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sigma-hole interactions\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Journal logoSTRUCTURAL
CHEMISTRY
ISSN: 2053-2296
Volume 78| Part 11| November 2022| Pages 578-590
https://doi.org/10.1107/S205322962200955X

Isolation and crystal and mol­ecular structures of [(C5H2Br3)2Fe], [(C5HBr4)2Fe] and [(C5Br5)(C5Br4HgBr)Fe]

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Tobias Blockhausa and Karlheinz Sünkela*

aChemistry, Ludwig-Maximilians-University Munich, Butenandtstrasse 5-13, Munich, D-81377, Germany
*Correspondence e-mail: suenk@cup.uni-muenchen.de

Edited by T. Roseveare, University of Sheffield, United Kingdom (Received 22 June 2022; accepted 28 September 2022; online 13 October 2022)

The reaction of [(C5H3Br2)2Fe] with lithium tetra­methyl­piperidinide (LiTMP) in a 1:10 molar ratio in tetra­hydro­furan yields, after quenching with C2H2Br4, a mixture of the polybromo­ferrocenes [C10H10–nBrnFe] with n = 4–9, from which single crystals of bis­(1,2,3-tri­bromo­cyclo­penta­dien­yl)iron(II), [Fe(C5H2Br3)2], and bis­(1,2,3,4-tetra­bromo­cyclo­penta­dien­yl)iron(II), [Fe(C5HBr4)2Fe], were obtained by a combination of chromatography and fractional crystallization. Treatment of `[C10(HgOAc)10Fe]' with KBr3 yields a mixture of polybromo­ferrocenes [C10H10–nBrnFe] with n = 8–10 and bromo­mercurioferrocenes [C10H9–nBrn(HgBr)Fe] with n = 7–9, from which single crystals of (1-bromo­mercurio-2,3,4,5-tetra­bromo­cyclo­penta­dien­yl)(1,2,3,4,5-penta­bromo­cyclo­penta­dien­yl)iron(II), [FeHgBr(C5Br4)(C5Br5)], were obtained by fractional crystallization. The crystal structures of all the com­pounds show Br⋯Br, Br⋯H and sometimes Br⋯Cp⋯π (Cp is a ring centroid) interactions, as well as π–π inter­actions. The findings are supported by Hirshfeld analyses.

CCDC references: 2210089; 2210088; 2210087

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1. Introduction

`Noncovalent inter­actions' are found in nearly all disciplines of chemistry, biochemistry and biology, and have been studied, at least in part, for quite a while (Hobza & Řezáč, 2016[Hobza, P. & Řezáč, J. (2016). Chem. Rev. 116, 4911-4912.]). This term brings together such apparently different inter­actions as hydrogen, halogen, lone-pair–π, anion–π, cation–π and π–π bonding, and these inter­actions can either act independently or co-operatively (Mahadevi & Sastry, 2016[Mahadevi, A. S. & Sastry, G. N. (2016). Chem. Rev. 116, 2775-2825.]; Portela & Fernández, 2021[Portela, S. & Fernández, I. (2021). Molecules, 26, 1885-1894.]). Among these, halogen bond(ing) has been studied continuously at a high level since about 1995. The last com­prehensive review dates back to 2016 (Cavallo et al., 2016[Cavallo, G., Metrangolo, P., Milani, R., Pilati, T., Priimagi, A., Resnati, G. & Terraneo, G. (2016). Chem. Rev. 116, 2478-2601.]). A look at SciFinder shows since then nearly 2000 new entries for the years 2021 and 2022, and already 492 entries with the concept `Halogen Bonding' (accessed on May 26th, 2022). The vast majority of these studies are centred on organic or biological systems, with a focus on crystal engineering (Mukherjee et al., 2014[Mukherjee, A., Tothadi, S. & Desiraju, G. R. (2014). Acc. Chem. Res. 47, 2514-2524.]). Relatively rarely studied were metal-containing systems (Brammer et al., 2008[Brammer, L., Mínguez Espallargas, G. & Libri, S. (2008). CrystEngComm, 10, 1712-1727.]), in particular, organometallic systems have so far been restricted to a few metal carbonyls, ruthenium-com­plexed aryl iodides (Kelly & Holman, 2022[Kelly, A. W. & Holman, K. T. (2022). Angew. Chem. Int. Ed. 61, e202115556.]) and one study on 1,1′-dihaloferrocenes (Shimizu & Ferreira da Silva, 2018[Shimizu, K. & Ferreira da Silva, J. (2018). Molecules, 23, 2959-2977.]). Our group has been working on polyhalogenated metallocenes for quite a while (Sünkel & Motz, 1988[Sünkel, K. & Motz, D. (1988). Angew. Chem. Int. Ed. Engl. 27, 939-941.]; Sünkel & Hofmann, 1992[Sünkel, K. & Hofmann, J. (1992). Organometallics, 11, 3923-3925.]; Sünkel et al., 1994[Sünkel, K., Kempinger, W. & Hofmann, J. (1994). J. Organomet. Chem. 475, 201-209.], 2015[Sünkel, K., Weigand, S., Hoffmann, A., Blomeyer, S., Reuter, C. G., Vishnevskiy, Y. V. & Mitzel, N. (2015). J. Am. Chem. Soc. 137, 126-129.]; Sünkel & Bernhartzeder, 2011[Sünkel, K. & Bernhartzeder, S. (2011). J. Organomet. Chem. 696, 1536-1540.]), and some very recent reports on the synthesis and crystal structure determinations of [(C5HnBr5–n)(C5H2Br3)Fe] (n = 1 or 2; Butler et al., 2021[Butler, I. R., Beaumont, M., Bruce, M. I., Zaitseva, N. N., Iggo, J. A., Robertson, C., Horton, P. N. & Coles, S. J. (2021). Aust. J. Chem. 74, 204-210.]; Butler, 2021[Butler, I. R. (2021). Organometallics, 40, 3240-3244.]) and [(C5HnBr5–n)(C5Br5)Fe] (n = 0 or 1; Rupf et al., 2022[Rupf, S. M., Dimitrova, I. S., Schröder, G. & Malischewski, M. (2022). Organometallics, 41, 1261-1267.]) prompted us to report on our synthetic and crystallographic studies of polybromo­ferrocenes. A special focus is made on the occurrence of halogen and hydrogen bonding in these systems.

2. Experimental

2.1. Synthesis and crystallization

2.1.1. Reaction of 1,1′,2,2′-tetra­bromo­ferrocene (1) with LiTMP in a 1:10 molar ratio and C2H2Br4

A solution of 1 (243 mg, 0.48 mmol) in tetra­hydro­furan (THF; 2 ml) was added to a freshly prepared solution of LiTMP (4.8 mmol) in THF (4 ml) at −30 °C. After stirring for 5 h, the temperature was lowered to −78 °C and C2H2Br4 (0.6 ml, 5.0 mmol) was added. With continuous stirring, the temperature was raised to ambient temperature over a period of 16 h. After this, water (10 ml) was added and the mixture was extracted with several 10 ml portions of CH2Cl2. The combined extracts were washed with water, then dried with MgSO4 and com­pletely evaporated in vacuo. The residue was taken up in the minimum amount of petroleum ether and chromatographed on an alumina column (20 × 2 cm), using petroleum ether as eluent. 21 fractions were collected and examined by mass spectroscopy and selected fractions were examined by 1H NMR spectroscopy (Figs. S1 and S2 in the supporting information). All fractions contained mixtures of poly­bromo­ferrocenes. While the first fraction consisted of a mix­ture of penta-, hexa- and hepta­bromo­ferrocene, the inter­­mediate fractions contained hexa-, hepta- and octa­bromo­ferrocene, and the last fraction was a mixture of hepta- and octa­bromo­ferrocene with traces of nona­bromo­ferrocene. Crystals of 1,1′,2,2′,3,3′-hexa­bromo­ferrocene (3) were ob­tained by slow evaporation of the sixth fraction in a refrigerator, and crystals of 1,1′,2,2′,3,3′,4,4′-octa­bromo­ferrocene (5) were obtained from the last fraction by the same method. All other fractions were also recrystallized from different solvents (petroleum ether, Et2O and CH2Cl2), but yielded neither crystals nor `pure' powders (according to 1H NMR spectra taken after redissolution).

Hexa­bromo­ferrocene (3). 1H NMR (270 MHz, CDCl3): δ 4.47 ppm (literature: 4.47 ppm; Butler, 2021[Butler, I. R. (2021). Organometallics, 40, 3240-3244.]). MS (DEI): m/z = 659.6 (calculated 659.5).

Octa­bromo­ferrocene (5). 1H NMR (400 MHz, DMSO-d6): δ 5.20 ppm. MS (DEI): m/z = 817.4 (calculated 817.3).

2.1.2. Reaction of `[C10(HgOAc)10Fe]' with KBr3

A suspension of `permercurated ferrocene' (2.78 g, ca 1 mmol) with KBr3, freshly prepared from KBr (1.19 g, 10 mmol) and Br2 (0.512 ml, 10 mmol) in water (100 ml), was stirred for 4 h at room temperature. After filtration, the residue was first washed with water and then extracted with di­chloro­methane. The combined extracts were evaporated in vacuo and the residue was placed on top of an alumina column. A 1:1 mixture of petroleum ether and di­chloro­methane eluted two yellow bands. The first fraction consisted, according to its mass spectrum (Fig. S3), of a mixture of deca-, nona- and octa­bromo­ferrocene, while the second fraction yielded a mixture of the bromo­mercurioferrocenes [C10HnBr9–nHgBrFe] with n = 0–2 (Fig. S4). The 1H NMR spectrum of the first fraction showed four weak signals, which unfortunately could not be assigned to individual com­pounds (Fig. S5). Recrystallization attempts with the first fraction yielded again only mixtures, while from the second fraction, crystals of [(C5Br5)(C5Br4HgBr)Fe] (8) could be obtained.

2.2. Refinement

Compound 3: SHELXT (Sheldrick, 2015a[Sheldrick, G. M. (2015a). Acta Cryst. A71, 3-8.]) provided the com­plete mol­ecule of 3 on the first run. The following difference Fourier synthesis (see Fig. S6 of the supporting information) showed two electron-density maxima (Q15 and Q16 in Fig. S6; d = 2.66 and 2.48 e Å−3) at radial distances of 1.54 and 1.40 Å from ring atoms C24 and C14, respectively. Despite these short distances (more typical for C—C bonds), we assigned these peaks to Br atoms (first named X1 and X2) with very low site-occupancy factors, since from the preceeding synthesis no other elements could have been present. The following refinement, however, showed rather short inter­molecular distances (2.581/3.328 and 2.955/3.106 Å) from these positions to atoms Br21i/Br22i and Br11i/Br12i, respectively [symmetry code: (i) x, y − 1, z] (Fig. S7). It was con­cluded that X1/X2 could not be present in the same mol­ecule as Br11/Br12/Br21 (and eventually Br22 also) and therefore it was assumed that com­pound 3 (with Br11–Br13 and Br21–Br23) cocrystallized with very small amounts (ca 3%) of com­pound 2 [with Br13–Br14 (= X2) and Br22–Br24 (= X1)], and this model was used for the subsequent refinements. The refinement procedure was as follows: first, it was assumed that all Br atoms would have the same isotropic U values and then the site-occupation factors for X1 = Br24/H24 and X2 = Br14/H14, as well as Br11/H11, Br12/H12, Br21/H21 and Br23/H23, were allowed to refine. The site-occupancy factors were then fixed at these values and the U values were allowed to refine freely for the main com­ponents even anisotropically. Any attempts to produce longer C14—Br14 and C24—Br24 `bonds' via the use of restraints met with failure. It should be noted at this point that the crystal structure of 1,1′,2,4-tetra­iodo­ferrocene showed a similar disorder and an apparent `bond shortening', which the authors were able to resolve (Evans et al., 2021[Evans, D. M., Hughes, D. D., Murphy, P. J., Horton, P. N., Coles, S. J., de Biani, F. F., Corsini, M. & Butler, I. R. (2021). Organometallics, 40, 2496-2503.]).

Compound 5: the measured crystal was recognized as a twin (two domains, rotated by 180° around 010) and a HKLF5 data file was created. The scale factor BASF refined to a final value of 0.17818. The refinement proceeded without any problems, and no signs of disorder were found.

Crystal data, data collection and structure refinement details of all com­pounds are summarized in Table 1[link].

Table 1
Experimental details

Experiments were carried out with Mo Kα radiation.
  3 5 8
Crystal data
Chemical formula [Fe(C5H2Br3)2] [Fe(C5HBr4)2] [FeHgBr(C5Br4)(C5Br5)]
Mr 656.69 817.25 1175.64
Crystal system, space group Triclinic, P[\overline{1}] Triclinic, P[\overline{1}] Monoclinic, P21/n
Temperature (K) 153 103 295
a, b, c (Å) 7.0903 (3), 7.4318 (5), 13.8071 (5) 6.9395 (2), 7.0548 (2), 8.9271 (3) 8.9784 (3), 14.0971 (4), 15.8485 (4)
α, β, γ (°) 88.745 (4), 84.993 (3), 77.728 (4) 67.577 (1), 76.160 (1), 86.461 (1) 90, 90.689 (1), 90
V (Å3) 708.21 (6) 392.06 (2) 2005.79 (10)
Z 2 1 4
μ (mm−1) 17.86 21.33 28.28
Crystal size (mm) 0.49 × 0.15 × 0.05 0.03 × 0.01 × 0.01 0.06 × 0.02 × 0.02
 
Data collection
Diffractometer Agilent XCalibur 2 Bruker D8 Venture Bruker D8 Venture
Absorption correction Multi-scan (CrysAlis PRO; Agilent, 2014[Agilent (2014). CrysAlis PRO. Agilent Technologies Ltd, Yarnton, Oxfordshire, England.]) Multi-scan (TWINABS; Bruker, 2012[Bruker (2012). APEX2, SAINT and TWINABS. Bruker AXS Inc., Madison, Wisconsin, USA.]) Multi-scan (SADABS; Krause et al., 2015[Krause, L., Herbst-Irmer, R., Sheldrick, G. M. & Stalke, D. (2015). J. Appl. Cryst. 48, 3-10.])
Tmin, Tmax 0.434, 1.000 0.180, 0.344 0.193, 0.332
No. of measured, independent and observed [I > 2σ(I)] reflections 9297, 3234, 2496 3772, 3772, 3107 33353, 4098, 3154
Rint 0.041 – 0.050
(sin θ/λ)max (Å−1) 0.649 0.832 0.625
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.043, 0.090, 1.09 0.037, 0.076, 1.06 0.036, 0.092, 1.06
No. of reflections 3234 3772 4098
No. of parameters 162 89 199
No. of restraints 2 0 0
H-atom treatment H-atom parameters constrained H-atom parameters constrained –
Δρmax, Δρmin (e Å−3) 2.31, −0.97 1.32, −1.31 1.63, −1.24
Computer programs: CrysAlis PRO (Agilent, 2014[Agilent (2014). CrysAlis PRO. Agilent Technologies Ltd, Yarnton, Oxfordshire, England.]), APEX2 (Bruker, 2012[Bruker (2012). APEX2, SAINT and TWINABS. Bruker AXS Inc., Madison, Wisconsin, USA.]), SAINT (Bruker, 2011[Bruker (2011). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]), SHELXT2014 (Sheldrick, 2015a[Sheldrick, G. M. (2015a). Acta Cryst. A71, 3-8.]) and SHELXL2018 (Sheldrick, 2015b[Sheldrick, G. M. (2015b). Acta Cryst. C71, 3-8.]).

3. Results and discussion

3.1. Synthesis

According to a recent review on haloferrocenes, there were only three heteroannularly substituted polybromo­ferrocenes known in 2018 (Butenschön, 2018[Butenschön, H. (2018). Synthesis, 50, 3787-3808.]): 1,1′-di­bromo­ferrocene, 1,1′,2-tri­bromo­ferrocene and deca­bromo­ferrocene. Since then, at least one isomer of each of the remaining [C10HnBr10–nFe] with n = 4–9 has been obtained, sometimes only as part of mixtures. There were two different synthetic approaches to achieve this: (i) stepwise li­thia­tion followed by elec­tro­philic quenching with `Br+', starting with 1,1′-di­­­bromo­ferrocene, or (ii) `permercuration' of ferrocene followed by treatment with KBr3. Both methods had their shortcomings, however. When 1,1′-di­bromo­ferrocene was treated with 2.1 equivalents of LiTMP in THF at low tem­per­ature, followed by electrophilic quenching with 1,1,2,2-tetra­bromo­ethane, a mixture of tri-, tetra-, penta-, hexa-, hepta- and octa­bromo­ferrocenes was obtained, from which the first two could be obtained in pure form (yields of 9.9 and 16.0%, respectively; Butler et al., 2021[Butler, I. R., Beaumont, M., Bruce, M. I., Zaitseva, N. N., Iggo, J. A., Robertson, C., Horton, P. N. & Coles, S. J. (2021). Aust. J. Chem. 74, 204-210.]). When the solvent was changed from THF to hexane, the electrophile to di­bromo­hexa­fluoro­propane and the temperature to room temperature, 1,1′,2,2′-tetra­bromo­ferrocene (1) was obtained in over 90% yield (Butler, 2021[Butler, I. R. (2021). Organometallics, 40, 3240-3244.]). Repeating the latter procedure on com­pound 1 gave rather high yields of 1,1′,2,2′,3,3′-hexa­bromo­ferrocene (3), contaminated, however, with hepta­bromo­ferrocene (4) and octa­bromo­ferrocene (5). All attempts to repeat this procedure on com­pound 3 met with failure, due to the very low solubility of this com­pound. On the other hand, the preparation of `permercurated ferrocenes' followed by the addition of KBr3, first reported in 1977, then later in 1994, 1997 and 2022, suffered from difficulties due to solubility problems (Boev & Dombrovskii, 1977[Boev, V. I. & Dombrovskii, A. V. (1977). Zh. Obshch. Khim. 47, 727-728.]; Han et al., 1994[Han, Y.-H., Heeg, M. J. & Winter, C. H. (1994). Organometallics, 13, 3009-3019.]; Neto et al., 1997[Neto, A. F., Borges, A. D. L., de Arruda Campos, P. & Miller, J. (1997). Synth. React. Inorg. Met.-Org. Chem. 27, 1543-1551.]; Rupf et al., 2022[Rupf, S. M., Dimitrova, I. S., Schröder, G. & Malischewski, M. (2022). Organometallics, 41, 1261-1267.]). For example, Han and co-workers showed that using Hg(O2CCF3)2 as the mercuration agent gave a `mixture of at least four partially brominated ferrocenes'. When they used Hg(O2CCH3)2 as the mercuration agent, deca­bromo­ferrocene (7) could be isolated in 60% yield, contaminated, however, with at least two partially brominated ferrocenes. Rupf and co-workers repeated this latter experiment and showed that besides 7 also nona­bromo­ferrocene (6) and nona­bromo(bromo­mer­cur­io)ferro­cene (8) were formed (based on 13C NMR spectroscopy; a closer look at Fig. S20 of their sup­porting information shows the additional formation of octa­bromo­ferrocene 5 and the bromo­mercurioferrocenes [C10HnBr9–nHgBrFe] with n = 1 and 2). When they used Hg(O2CC3H7)2, they apparently obtained a mixture of 7 and 8 with no other contaminants (based on NMR and IR). Neto and co-workers reported the use of Hg(O2CCCl3)2 as the mercuration agent, the transformation of the apparently formed [C10(HgO2CCl3)10Fe] to the deca­chloro­mercurio­ferrocene, followed by reaction with KBr3 to give pure 7 [characterization by NMR and IR spectroscopy, and elemental analysis (C and Fe)].

We decided to look at the li­thia­tion reactions with LiTMP as the li­thia­ting reagent, C2H2Br4 as the brominating agent and THF as the reaction medium at low temperatures again. We started with a solution of 1,1′,2,2′-tetra­bromo­ferrocene (1; purity > 95%) in THF and treated it with ten molar equivalents of LiTMP, followed by the addition of tetra­bromo­ethane. After standard work-up, a chromatographic separation was attempted. Since no band formation was recognizable, 21 fractions with equal volume were collected. Fractions 1, 10, 12 and 21 were examined by mass spectrometry (Fig. S1), while fractions 4, 6, 8 and 21 were studied by NMR spectroscopy (Fig. S2). All fractions were left standing in open vials for slow evaporation of the solvent. From these crystallization attempts, fractions 1, 6 and 21 gave crystals. The observation that some com­pounds were present in nearly all fractions is most likely due to the low solubility in the eluting solvent, which led to `smearing' over the length of the chromatography column. The use of different solvent mixtures for elution (PE/Et2O, PE/THF and PE/CH2Cl2; PE is petroleum ether) increased the solubility, but did not improve the resolution of the com­pounds. This problem might have been overcome by the use of high-performance liquid chromatography (HPLC); however, this was not available to us.

The mass spectrum of fraction 1 showed the presence of 2 (m/z = 579.7), 3 (m/z = 659.6) and 4 (m/z = 737.5), with 2 as the main com­ponent. In both of fractions 10 and 12, 4 was the main com­ponent, contaminated by 2 (traces), 3 and 5 (m/z = 817.5). Finally, the mass spectrum of fraction 21 showed 5 as the main com­ponent, contaminated by 4 and traces of 6 (m/z = 895.2). The 1H NMR spectra of fractions 4, 6 and 8 showed different mixtures of com­pounds 3 (δ = 4.47) and 4 (δ = 4.72 and 4.43) [assignments based on Butler (2021[Butler, I. R. (2021). Organometallics, 40, 3240-3244.])]. The 1H NMR spectrum of fraction 21 (in dimethyl sulfoxide) showed three very weak signals at δ = 5.33, 5.20 and 4.76, which might be assigned to 4 and 5 by com­parison with the mass spectra (no other NMR data in this solvent were available). The crystals obtained from fraction 1 suffered from disorder or cocrystallization effects, which could not be properly resolved. The crystals from fraction 6 also showed disorder, which could, however, be successfully modelled as cocrystallization of com­pounds 3 (ca 97% contribution) and 2. Fraction 21 yielded pure crystals of com­pound 5.

Fig. 1[link] shows the structural formulae of the com­pounds discussed in this study.

[Figure 1]
Figure 1
The structural formulae of com­pounds 1–8.

We also repeated the permercuration of ferrocene according to Winter and co-workers, using Hg(O2CCH3)2 as the mercurating agent and di­chloro­ethane as the solvent, followed by bromination with KBr3. Chromatography of the crude reaction product yielded two fractions (Han et al., 1994[Han, Y.-H., Heeg, M. J. & Winter, C. H. (1994). Organometallics, 13, 3009-3019.]). The first contained, according to its mass spectrum (Fig. S3), a mixture of bromo­ferrocenes 5–7 (with com­pound 6 dominating), while the second consisted of a mixture of bromo­mercurioferrocenes [C10HnBr10–nHgFe] (n = 0–2; Fig. S4). Fig. S5 shows the 1H NMR spectrum of the first fraction, which apparently consists of four proton-containing substances, of which one dominates. Although we did not perform these experiments, it can be assumed that com­pounds 5–7 are formed by further bromination of [C10HnBr10–nHgFe]. Therefore, we conclude that neither the permercuration nor the bromination reactions are com­plete. Although all fractions were used for crystallization attempts, only crystals of com­pound 8 could be obtained.

3.2. Mol­ecular structures

An intensely debated topic since the very early days of ferrocene chemistry was the question of the relative stability of the eclipsed and staggered conformers of this mol­ecule. While the very first crystal structure determination of ferrocene (Fischer & Pfab, 1952[Fischer, E. O. & Pfab, W. (1952). Z. Naturforsch. 7, 377-379.]) hinted at a staggered geometry, the most recent low-temperature IR and XANES (X-ray absorption near edge structure) spectra, as well as DFT (density functional theory) calculations showed that the eclipsed conformation is the energy minimum (Bourke et al., 2016[Bourke, J. D., Islam, M. T., Best, S. P., Tran, C. Q., Wang, F. & Chantler, C. T. (2016). J. Phys. Chem. Lett. 7, 2792-2796.]; Silva et al., 2014[Silva, P. A., Maria, T. M. R., Nunes, C. M., Eusébio, M. E. S. & Fausto, R. (2014). J. Mol. Struct. 1078, 90-105.]). For ferrocenes substituted on both rings, an additional conformational isomerism arises from the possibility of different relative positions of the substituents (Scheme 1[link]).

[Scheme 1]

While theoretical calculations on 1,1′-di­bromo­ferrocene showed that the two C2 isomers (II and III in Scheme 1) are minimum conformations (Silva et al., 2014[Silva, P. A., Maria, T. M. R., Nunes, C. M., Eusébio, M. E. S. & Fausto, R. (2014). J. Mol. Struct. 1078, 90-105.]), in the crystal structure, only the less favourable C2v structure (I in Scheme 1[link]) was obtained (Hnetinka et al., 2004[Hnetinka, C. A., Hunter, A. D., Zeller, M. & Lesley, M. J. G. (2004). Acta Cryst. E60, m1806-m1807.]). To obtain an overview of the `realized' structures, a Cambridge Structural Database (CSD; Groom et al., 2016[Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171-179.]) search on ferrocenes with at least one halogen substituent on each ring was undertaken. This search delivered 40 hits, of which 14 contained only halogen substituents: all four FdX2, two FdX3, three FdX4, FdCl6, FdBr9 and FdBr10; FdCl2 was determined twice and FdI4 exists as two positional isomers; `Fd' is a common abbreviation for ferrocenes with substituents on both rings, while `Fc' symbolizes ferrocenes with substituents only on one ring; strictly speaking, `Fc' stands only for the [C10H9Fe] residue, while `Fd' symbolizes a [(C5H4)2Fe] group. The four 1,1′-dihaloferrocenes have been discussed already with respect to supra­molecular inter­actions in general and halogen bonding in particular (Shimizu & Ferreira da Silva, 2018[Shimizu, K. & Ferreira da Silva, J. (2018). Molecules, 23, 2959-2977.]). All these com­pounds, except for FdI2, FdBr9 and FdBr10, showed eclipsed conformations (or nearly eclipsed in the case of FdBr3 and FdI3, with torsion angles of ca 14°). Within this group of eclipsed structures, most showed the apparent `higher energy' conformations I and IV, respectively. Only FdBr3, FdI3 and FdI4 crystallized in the most stable form VI. Table 2[link] gives an overview on these structures.

Table 2
Overview of the CSD structures of polyhaloferrocenes substituted on both rings

Chemical formula Abbreviation in this text Refcode in the CSD Conformation Reference
C10H8F2Fe FdF2 RACROF Eclipsed, I Inkpen et al. (2015[Inkpen, M. S., Du, S., Hildebrand, M., White, A. J. P., Harrison, N. M., Albrecht, T. & Long, N. J. (2015). Organometallics, 34, 5461-5469.])
C10H8Cl2Fe FdCl2 DUTSUH, DUTSUH01 Eclipsed, I Bryan & Leadbetter (1986[Bryan, R. F. & Leadbetter, A. J. (1986). American Crystallographic Association, Abstracts (Winter), 14, 28b.]); Inkpen et al. (2015[Inkpen, M. S., Du, S., Hildebrand, M., White, A. J. P., Harrison, N. M., Albrecht, T. & Long, N. J. (2015). Organometallics, 34, 5461-5469.])
C10H8Br2Fe FdBr2 BIPDOU Eclipsed, I Hnetinka et al. (2004[Hnetinka, C. A., Hunter, A. D., Zeller, M. & Lesley, M. J. G. (2004). Acta Cryst. E60, m1806-m1807.])
C10H8I2Fe FdI2 KOPFAY Staggered Roemer & Nijhuis (2014[Roemer, M. & Nijhuis, C. A. (2014). Dalton Trans. 43, 11815-11818.])
C10H7Br3Fe FdBr3 UTOBIR Nearly eclipsed, VI Butler et al. (2021[Butler, I. R., Beaumont, M., Bruce, M. I., Zaitseva, N. N., Iggo, J. A., Robertson, C., Horton, P. N. & Coles, S. J. (2021). Aust. J. Chem. 74, 204-210.])
C10H7I3Fe FdI3 EZAWUA Nearly eclipsed, VI Evans et al. (2021[Evans, D. M., Hughes, D. D., Murphy, P. J., Horton, P. N., Coles, S. J., de Biani, F. F., Corsini, M. & Butler, I. R. (2021). Organometallics, 40, 2496-2503.])
C10H6Cl4Fe FdCl4 CEVBEK Eclipsed, IV Sato et al. (1984[Sato, K., Konno, M. & Sano, H. (1984). Chem. Lett. 13, 17-20.])
C10H6Br4Fe FdBr4 UTOBUD Eclipsed, IV Butler et al. (2021[Butler, I. R., Beaumont, M., Bruce, M. I., Zaitseva, N. N., Iggo, J. A., Robertson, C., Horton, P. N. & Coles, S. J. (2021). Aust. J. Chem. 74, 204-210.])
C10H6I4Fe- FdI4 EZAWOU Eclipsed, VI Evans et al. (2021[Evans, D. M., Hughes, D. D., Murphy, P. J., Horton, P. N., Coles, S. J., de Biani, F. F., Corsini, M. & Butler, I. R. (2021). Organometallics, 40, 2496-2503.])
C10H4Cl6Fe FdCl6 DUTSUG No data in CSD Bryan & Leadbetter (1986[Bryan, R. F. & Leadbetter, A. J. (1986). American Crystallographic Association, Abstracts (Winter), 14, 28b.])
C10HBr9Fe FdBr9 FEFZAV Staggered Rupf et al. (2022[Rupf, S. M., Dimitrova, I. S., Schröder, G. & Malischewski, M. (2022). Organometallics, 41, 1261-1267.])
C10Br10Fe FdBr10 FEFYUO staggered Rupf et al. (2022[Rupf, S. M., Dimitrova, I. S., Schröder, G. & Malischewski, M. (2022). Organometallics, 41, 1261-1267.])

Compound 3 crystallizes in the triclinic space group P[\overline{1}], with one mol­ecule in the asymmetric unit. Fig. 2[link] shows the major orientation of the disordered mol­ecule. As in most polyhaloferrocene structures (see Table 2[link]), the cyclo­penta­dienyl (Cp) rings are nearly perfectly eclipsed, planar and parallel to each other. All Br atoms are shifted slightly to the distal side of the Cp rings with respect to the Fe atom.

[Figure 2]
Figure 2
Top view of the mol­ecular structure of com­pound 3 (major orientation), with displacement ellipsoids drawn at the 30% probability level.

Compound 5 also crystallizes in the triclinic space group P[\overline{1}], however, as a twin with half a mol­ecule in the asymmetric unit and the Fe atom residing on an inversion centre (Fig. 3[link]). As a consequence of this, the Cp rings are perfectly staggered, with the two C—H bonds in relative transoid positions. Both Cp rings are planar and parallel to each other and the Br atoms are all shifted to the distal sides of the Cp rings, however, to a smaller extent than in the eclipsed structures mentioned before. The iron–centroid distance (determined within PLATON) also seems to be more dependent on the relative orientation of the Cp rings than on the degree of bromination. Table 3[link] collects important geometrical parameters of several polybromo­ferrocenes from the literature, together with those of com­pounds 3, 5 and 8.

Table 3
Important geometrical parameters of com­pounds 3, 5 and 8 in com­parison with literature data for closely related com­pounds

FdBr2 is 1,1′-di­bromo­ferrocene; `Ct' is the abbreviation for the `centroid' of the Cp rings, as calculated by the corresponding feature in PLATON (Spek, 2020[Spek, A. L. (2020). Acta Cryst. E76, 1-11.]); δ (Br—Cp) is the distance of the Br atoms from the Cp plane.
Compound C—Br (Å) Fe—C (Å) Fe—Ct (Å) Ct—Fe—Ct′ (°) Br—Ct—Ct′—Br′ (°) δ (Br—Cp) (Å) Reference
FdBr2 1.882 (4)/1.866 (4) 2.035 (4)–2.054 (4) 1.6500 (5)/1.6483 (5) 177.71 (4) 1.55 (1) 0.137 (6)/0.082 (6) A
1 1.873 (2)–1.877 (2) 2.036 (2)–2.052 (2) 1.6482 (8) 177.75 (6) 1.59 (8) 0.130 (1)–0.149 (1)) B
3 1.862 (7)–1.881 (6) 2.033 (6)–2.064 (6) 1.653 (3)/1.654 (3) 176.3 (2) 2.09–2.38 0.123 (1)–0.168 (1) This work
5 1.865 (3)–1.874 (3) 2.036 (6)–2.056 (3) 1.6449 (16) 180 35.9–36.2 0.037 (1)–0.096 (1) This work
6 1.861 (10)–1.888 (11) 2.02 (1)–2.06 (1) 1.637 (1)/1.642 (1) 178.5 (3) 33.4 (5) 0.005 (1)–0.146 (1) C
7 1.863 (4)–1.874 (4) 2.041 (4)–2.049 (4) 1.645 (2) 180 33.8 (2) 0.085 (1)–0.142 (1) C
8 1.852 (9)–1.880 (8) 2.024 (8)–2.049 (8) 1.641 (4)/1.644 (4) 178.4 (7) 30.5 (1)–31.6 (1) 0.004 (14)–0.142 (13) This work
8+·AsF6 1.845 (8)–1.865 (8) 2.066 (8)–2.116 (8) 1.703 (4)/1.708 (4) 178.9 (5) 32.5 (4) −0.056 (1)–0.062 (1) C
References: (A) Hnetinka et al. (2004[Hnetinka, C. A., Hunter, A. D., Zeller, M. & Lesley, M. J. G. (2004). Acta Cryst. E60, m1806-m1807.]); (B) Butler et al. (2021[Butler, I. R., Beaumont, M., Bruce, M. I., Zaitseva, N. N., Iggo, J. A., Robertson, C., Horton, P. N. & Coles, S. J. (2021). Aust. J. Chem. 74, 204-210.]); (C) Rupf et al. (2022[Rupf, S. M., Dimitrova, I. S., Schröder, G. & Malischewski, M. (2022). Organometallics, 41, 1261-1267.]).
[Figure 3]
Figure 3
Top view of the mol­ecular structure of com­pound 5, showing a whole mol­ecule, with displacement ellipsoids drawn at the 30% probability level.

Compound 8 crystallizes in the monoclinic space group P21/n, with one mol­ecule in the asymmetric unit (Fig. 4[link]). The C10—Hg1—Br10 bond deviates slightly from being linear [171.0 (2)°]. The Cp rings are planar and parallel to each other, while their relative orientation is staggered. The distances from Fe1 to both Cp ring centroids are identical within 1σ. Except for atoms Br5 and Hg1, which are within the Cp ring planes, all the ring substituents are shifted again to the distal sides of the Cp rings. In com­parison with the structure of the ferricenium salt 8+·AsF6−, the C—Br bonds are slightly longer, while the iron–centroid distances are significantly shorter in 8, which is quite usual when com­paring ferrocenes with their oxidized counterparts (Rupf et al., 2022[Rupf, S. M., Dimitrova, I. S., Schröder, G. & Malischewski, M. (2022). Organometallics, 41, 1261-1267.]).

[Figure 4]
Figure 4
Top view of the mol­ecular structure of 8, with displacement ellipsoids drawn at the 30% probability level.

For all three com­pounds, an analysis with PLATON showed no residual solvent-accessible voids (Spek, 2020[Spek, A. L. (2020). Acta Cryst. E76, 1-11.]).

3.3. Hirshfeld analysis and inter­molecular contacts

To gain some insight into the inter­molecular inter­actions at work in these com­pounds, a Hirshfeld analysis was undertaken, using the program CrystalExplorer (Spackman et al., 2021[Spackman, P. R., Turner, M. J., McKinnon, J. J., Wolff, S. K., Grimwood, D. J., Jayatilaka, D. & Spackman, M. A. (2021). J. Appl. Cryst. 54, 1006-1011.]).

Fig. 5[link] shows the Hirshfeld surfaces of the three com­pounds, together with the closest contact atoms (within 3.8 Å).

[Figure 5]
Figure 5
Hirshfeld surfaces of com­pounds 3 (left), 5 (middle) and 8 (right), together with the closest contact atoms. Red spots show very close contacts between atoms inside and outside the Hirshfeld surface. The Hg com­pound differs from the other two by the appearance of such a red spot over the plane of the Cp ring.

The so-called `fingerprint plots', which summarize all contacts between atoms inside and outside the Hirshfeld surface (Spackman & McKinnon, 2002[Spackman, M. A. & McKinnon, J. J. (2002). CrystEngComm, 4, 378-392.]; Spackman & Jayatilaka, 2009[Spackman, M. A. & Jayatilaka, D. (2009). CrystEngComm, 11, 19-32.]), are shown in Fig. 6[link]. A common feature of all three plots is the occurrence of a red stripe around the main diagonal, reaching from ca de/di = 1.8/1.8 to 2.2/2.2, which corresponds to a large number of Br⋯Br contacts (de + di = 3.6 to 4.4 Å; the sum of the van der Waals radii of two Br atoms is 3.70 Å).

[Figure 6]
Figure 6
Fingerprint plots of com­pounds 3 (left), 5 (middle) and 8 (right). A red colour symbolizes a large number of points on the Hirshfeld surface at the corresponding de/di pair, green inter­mediate numbers and blue small numbers.

The very different appearance of these plots is mainly due to the decreasing number of H atoms present. Table 4[link] and Fig. S8 of the supporting information provide a more detailed analysis, showing the different contributions of the individual element contacts.

Table 4
Individual contributions (%) of the different inter­actions present in the crystal structures of FdBr2, 3, 5 and 8

Compound C⋯H C⋯Br C⋯C H⋯H H⋯Br Br⋯Br Hg⋯Br
FdBr2* 17.1 3.7 0 37.3 39.6 2.3 –
1** 6.2 1.6 6.0 14.2 52.4 19.6 –
3 3.3 4.0 5.9 0.8 48.0 38.2 –
5 1.2 6.8 5.9 0.9 20.9 64.3  
8 – 10.7 3.5 – – 77.7 8.2
Notes: (*) taken from Shimizu & Ferreira da Silva (2018[Shimizu, K. & Ferreira da Silva, J. (2018). Molecules, 23, 2959-2977.]); (**) calculated from the downloaded CIF file, available from the CCDC as CSD refcode UTOBUB.

Due to purely statistical effects (there are eight H atoms in FdBr2, four in 3, two in 5 and none in 8), the absolute numbers cannot be com­pared directly. However, it is quite obvious that the importance of C⋯H and especially H⋯H contacts decreases drastically with increasing bromine content, while the importance of Br⋯Br contacts increases in the same direction. At the same time, it appears quite inter­esting that H⋯Br contacts are very important in all com­pounds where H atoms are present.

To obtain a more detailed picture of the individual inter­actions, a Mercury analysis was undertaken (Macrae et al., 2020[Macrae, C. F., Sovago, I., Cottrell, S. J., Galek, P. T. A., McCabe, P., Pidcock, E., Platings, M., Shields, G. P., Stevens, J. S., Towler, M. & Wood, P. A. (2020). J. Appl. Cryst. 53, 226-235.])

3.3.1. Hydrogen bonds

The structures of the known polyhaloferrocenes collected in Table 2[link] show three different patterns of hydrogen bonding (Scheme 2): Type A is observed in the structures of FdF2, FdBr3, FdI3, FdCl4, FdBr4 and FdBr9. All FdX2, as well as iodo­ferrocenes and FdBr4, show Type B, while Type C is seen only in the two trihaloferrocenes.

[Scheme 2]

When using the standard settings of Mercury, no hydrogen bonds are indicated for com­pound 3. However, when increasing the limit by 0.2 Å, four (obviously very weak) hydrogen bonds appear [Fig. 7[link] (left) and Table 5[link]].

Table 5
Hydrogen-bond parameters (Å, °) in com­pounds 3 and 5

Calculated with SHELXL2018 (Sheldrick, 2015b[Sheldrick, G. M. (2015b). Acta Cryst. C71, 3-8.]) command HTAB.
  D—H⋯A D—H H⋯A D⋯A D—H⋯A
3 C24—H24⋯Br21i 0.95 3.10 3.965 (9) 151.8
  C25—H25⋯Br23ii 0.95 3.13 3.874 136.5
  C14—H14⋯Br11i 0.95 3.20 4.046 (9) 149.8
  C15—H15⋯Br13ii 0.95 3.24 3.927 (8) 131.8
5 C5—H5⋯Br2i 0.95 2.985 3.786 142.93
  C5—H5⋯Br3i 0.95 3.015 3.809 141.91
Symmetry codes: (i) x, y − 1, z; (ii) x − 1, y, z.
[Figure 7]
Figure 7
(Partial) packing plots (Mercury; Macrae et al., 2020[Macrae, C. F., Sovago, I., Cottrell, S. J., Galek, P. T. A., McCabe, P., Pidcock, E., Platings, M., Shields, G. P., Stevens, J. S., Towler, M. & Wood, P. A. (2020). J. Appl. Cryst. 53, 226-235.]) of com­pounds 3 (left), viewed along c, and 5 (right), viewed along a, showing the inter­molecular hydrogen bonds. Colour codes as defined by Mercury: carbon dark grey, hydrogen light grey, iron orange and bromine brown; the red lines are unexpanded contacts and the cyan lines are expanded contacts.

As can be seen from Fig. 7[link] (left), the atom pairs H14/Br11 and H24/Br21 connect the individual mol­ecules in the y direction, while the pairs H15/Br13 and H25/Br23 join them in the x direction. Atoms Br12 and Br22 are not involved in hydrogen bonding.

In com­pound 5, the standard settings of Mercury suffice to show that only atom H5 (and, of course, its inversion-symmetry-generated counterpart H5′) engages in a symmetrical bifurcated hydrogen bond (Type A in Scheme 2) with atoms Br2 and Br3 [Fig. 7[link] (right) and Table 5[link]]. As the figure shows, these inter­actions join individual mol­ecules in the y direction.

3.3.2. Halogen bonding and other Br⋯Br inter­actions

In the discussion of halogen bonding, a distinction is usually made between XB Type I and XB Type II. According to the IUPAC and IUCr classifications, Type I contacts are geometry based, arising from close-packing requirements, while Type II arise from inter­actions between an electron-rich region on one halogen atom and an electron-deficient region on the other. The distinction can be made on the basis of the angles Θ1 and Θ2, which occur at halogen atoms X and X′ of R—X⋯X′—R′, and their difference (Scheme 3).

[Scheme 3]

Usually it is assumed that for 0 < |Θ1 – Θ2| < 15°, a Type I contact is formed, while for Type II contacts, 30 < |Θ1 – Θ2| < 105° is found, and only the latter are regarded as real halogen bonds (Cavallo et al., 2016[Cavallo, G., Metrangolo, P., Milani, R., Pilati, T., Priimagi, A., Resnati, G. & Terraneo, G. (2016). Chem. Rev. 116, 2478-2601.]). In a more recent article, a distinction into Types I–IV was suggested, but was still based on these angles (Ibrahim et al., 2022[Ibrahim, M. A. A., Saeed, R. R. A., Shehata, M. N. I., Ahmed, M. N., Shawky, A. M., Khowdiary, M. M., Elkaeed, E. B., Soliman, M. E. S. & Moussa, N. A. M. (2022). Int. J. Mol. Sci. 23, 3114-3130.]): Type I: 90 < Θ1 ≃ Θ2 < 180°; Type II: Θ1 = 180° and Θ2 = 90°; Type III: Θ1 ≃ Θ2 = 180°; Type IV: Θ1 ≃ Θ2 = 90° (obviously, Types III and IV are only extrema of the more general Type I). The forces behind these attractions are either van der Waals (Type I), electrostatic (Type II) or dispersion (Types III and IV) forces. It was further found that `the Type I inter­actions were more frequent at the shortest distances' (Cavallo et al., 2016[Cavallo, G., Metrangolo, P., Milani, R., Pilati, T., Priimagi, A., Resnati, G. & Terraneo, G. (2016). Chem. Rev. 116, 2478-2601.]). Table 6[link] collects the structural parameters of com­pounds 3, 5 and 8, while Figs. S9–S11 show Mercury representations of these inter­actions.

Table 6
Characteristics of the Br⋯Br inter­actions found in com­pounds 1, 3, 5, 8 and FdBr2

Compound R—Br⋯Br′—R′ Br⋯Br (Å) Θ1 (°) Θ2 (°) |Θ1 − Θ2| (°) XB Type
FdBr2* C1—Br1⋯Br2—C6 3.586 89.7 153.1 63.2 II
1** C1—Br1⋯Br2—C2 3.564 145.2 156.4 11.2 I
3 C13—Br13⋯Br11—C11 3.617 135.2 153.8 18.6 Quasi-Type I/Type II
  C23—Br23⋯Br11—C11 3.582 137.3 143.3 6.0 I
  C23—Br23⋯Br21—C21 3.594 146.9 141.8 5.1 I
  C13—Br13⋯Br23—C23 3.656 84.7 85.1 0.4 IV
  C11—Br11⋯Br21—C21 3.657 85.2 84.4 0.8 IV
5 C1—Br1⋯Br3—C3 3.518 160.8 124.8 36.0 II
  C2—Br2⋯Br4—C4 3.538 128.9 163.8 34.9 II
8 C1—Br1⋯Br9—C9 3.545 154.8 117.4 37.4 II
  C4—Br4⋯Br6—C6 3.634 117.7 113.1 4.6 I
  C4—Br4⋯Br7—C7 3.657 171.4 112.5 58.9 II
  C3—Br3⋯Br6—C6 3.521 174.1 65.9 108.2 II
  C7—Br7⋯Br10—Hg1 3.658 167.0 97.9 69.1 II
  C9—Br9⋯Br10—Hg1 3.642 109.4 163.4 54.0 II
Notes: (*) taken from Shimizu & Ferreira da Silva (2018[Shimizu, K. & Ferreira da Silva, J. (2018). Molecules, 23, 2959-2977.]); (**) calculated from the downloaded CIF file, available from the CCDC as CSD refcode UTOBUB.

All the listed Br⋯Br contacts in Table 6[link] are well below the sum of the van der Waals radii (3.70 Å; Bondi, 1964[Bondi, A. (1964). J. Phys. Chem. 68, 441-451.]). When using the |Θ1 – Θ2| criterion, most inter­actions classified as Type II are also `real' halogen bonds. To look at the structural consequences of this halogen bonding, a visualization of the packing plots should be helpful.

Fig. 8[link] shows how the Br⋯Br inter­actions join the individual mol­ecules of com­pound 3 in the direction of the xy diagonal (b–a vector). It can also be seen that there are two intramol­ecular Br⋯Br contacts of Type IV, emphasized in italic in Table 5[link]. Two Br atoms (Br12 and Br22) are not involved in Br⋯Br inter­actions. Fig. 9[link] shows that in com­pound 5 the Br⋯Br contacts join the individual mol­ecules in the z direction. All eight Br atoms are involved in Br⋯Br inter­actions. In addition, there is also some π–π stacking in the x direction; the centroids of two adjacent Cp rings are only 3.773 Å apart, while the ring planes have an inter­planar distance of 3.507 Å (corresponding to an angle of 21.6° between the Ct—Ct′ vector and the plane normal).

[Figure 8]
Figure 8
Packing plot of com­pound 3, viewed along c. Colour codes as defined by Mercury: carbon dark grey, hydrogen light grey, iron orange and bromine brown; the red lines are unexpanded contacts and the cyan lines are expanded contacts.
[Figure 9]
Figure 9
Packing plot of com­pound 5, viewed along b. Colour codes as defined by Mercury: carbon dark grey, hydrogen light grey, iron orange and bromine brown; the red lines are unexpanded contacts and the cyan lines are expanded contacts.

In bromo­mercurio com­pound 8, matters are a bit more com­plicated. Fig. 10[link] shows that Br⋯Br contacts join the individual mol­ecules in all directions. All Br atoms, except for Br2, Br5 and Br8, are involved in Br⋯Br contacts.

[Figure 10]
Figure 10
Packing plots of com­pound 8, viewed along a (left) and along b (right). Colour codes as defined by Mercury: carbon dark grey, hydrogen light grey, iron orange and bromine brown; the red lines are unexpanded contacts and the cyan lines are expanded contacts.

But there are more inter­actions involving Br atoms. First there are Hg⋯Br contacts, shown in Fig. 11[link]. The Hg1⋯Hg1 distance is 4.4944 (6) Å and therefore any mercurophilic inter­actions (Schmidbaur & Schier, 2015[Schmidbaur, H. & Schier, A. (2015). Organometallics, 34, 2048-2066.]) can be excluded. In the crystal of the ferricenium com­plex 8+·AsF6−, there is also a Hg2Br2 ring with significantly shortened inter­molecular Hg⋯Br contacts of 3.061 Å and a Hg⋯Hg distance of 3.993 Å (Rupf et al., 2022[Rupf, S. M., Dimitrova, I. S., Schröder, G. & Malischewski, M. (2022). Organometallics, 41, 1261-1267.]). Furthermore, there are Br⋯π contacts of 3.543 Å to a close Cp ring, in addition to a weak π–π inter­action between two Cp rings (Fig. 12[link]); π–π stacking occurs between two inversion-related C5Br5 rings. Since the difference between the Ct—Ct′ distance of 3.756 Å and the perpendicular distance between the Cp ring planes (3.690 Å) is rather small (corresponding to an angle of 10.8° between the Ct—Ct′ vector and the plane normal), it can be regarded as a `true' π–π inter­action (though rather weak).

[Figure 11]
Figure 11
The Hg2Br2 ring in com­pound 8. Colour codes as defined by Mercury: carbon dark grey, hydrogen light grey, iron orange and bromine brown; the red lines are unexpanded contacts and the cyan lines are expanded contacts. Generic atom labels without symmetry codes ahve been used.
[Figure 12]
Figure 12
Partial packing diagram of com­pound 8, showing the Br⋯π and π–π contacts (Å). Colour codes as defined by Mercury: carbon dark grey, hydrogen light grey, iron orange, mercury blue and bromine brown; the red lines are unexpanded contacts and the cyan lines are expanded contacts. Ct1′/Ct1′′ and Ct2′/Ct2′′ are the centroids of inversion-related cyclo­penta­dienyl rings, with one Fe atom between Ct1′ and Ct2′, and another between Ct1′′ and Ct2′′.

A similar Br⋯π inter­action was found in the structure of FdBr2; however, it was, with a Br⋯centroid distance of 3.824 Å, substanti­ally weaker (Shimizu & Ferreira da Silva, 2018[Shimizu, K. & Ferreira da Silva, J. (2018). Molecules, 23, 2959-2977.]).

3.3.3. Co-operativity between H⋯Br and Br⋯Br contacts

The importance of co-operativity in noncovalent inter­actions in general (Mahadevi & Sastry, 2016[Mahadevi, A. S. & Sastry, G. N. (2016). Chem. Rev. 116, 2775-2825.]) and for the inter­play of halogen and hydrogen bonds (Decato et al., 2021[Decato, D. A., Riel, A. M. S., May, J. H., Bryantsev, V. S. & Berryman, O. B. (2021). Angew. Chem. Int. Ed. 60, 3685-3692.]; Portela & Fernández, 2021[Portela, S. & Fernández, I. (2021). Molecules, 26, 1885-1894.]) in particular has been recognized in recent years and has been modelled by DFT calculations. This inter­play has also been discussed for the 1,1′-dihaloferrocenes (Shimizu & Ferreira da Silva, 2018[Shimizu, K. & Ferreira da Silva, J. (2018). Molecules, 23, 2959-2977.]). In the preceding sections, we have discussed the individual contributions in com­pounds 3 and 5, and a look at Fig. 13[link] (and Tables 4[link] and 5[link]) shows that also in these com­pounds HB and XB work together on the same halogen atoms.

[Figure 13]
Figure 13
Co-operativity of hydrogen and halogen bonding in com­pounds 3 and 5. Colour codes as defined by Mercury: carbon dark grey, hydrogen light grey, iron orange and bromine brown; the red lines are unexpanded contacts and the cyan lines are expanded contacts.
3.3.4. Energetics of the inter­molecular inter­actions found in com­pounds 3, 5 and 8

The program CrystalExplorer allows for the calculation of inter­action energies using the DFT program TONTO at the HF/3-21G level (Mackenzie et al., 2017[Mackenzie, C. F., Spackman, P. R., Jayatilaka, D. & Spackman, M. A. (2017). IUCrJ, 4, 575-587.]). Fig. 14[link] shows the results of calculations for com­pounds 3 and 5 (apparently, due to the presence of Hg, the program cannot calculate wavefunctions for com­pound 8).

[Figure 14]
Figure 14
Inter­action energies (HF/3-21G) for com­pounds 3 (left) and 5 (right) (standard program settings). The colour codes in the images refer to the tables below them.

Inspection of the numerical values shows that the total inter­action energies are stronger for com­pound 3. This is apparently due to the larger repulsion terms for 5, because both the largest dispersion and the largest electrostatic terms are found in com­pound 5. Another graphical representation (`energy frameworks') of the individual contributions can be seen in Fig. 15[link].

[Figure 15]
Figure 15
Energy frameworks (Coulombic energy in red, dispersion energy in green and total energy in blue) for com­pounds 3 (top) and 5 (bottom).
3.3.5. Comparison with halogen bonding in other haloferrocenes FdXn with X ≠ Br and n > 2

At this point, it seems worthwhile to look at the occurrence of halogen bonding in the other polyhaloferrocenes mentioned in Table 2[link]. As mentioned already, this study has been performed for the 1,1′-dihaloferrocenes before, and therefore these structures will not be considered here again. Instead, the structure of the homoannularly substituted penta­bromo­ferrocene (FcBr5; Sünkel & Bernhartzeder, 2011[Sünkel, K. & Bernhartzeder, S. (2011). J. Organomet. Chem. 696, 1536-1540.]) is included (Table 7[link]). All the listed X⋯X contacts are below the sum of the van der Waals radii and of Type II except for the chloro com­pound (0.004 Å longer than this sum and Type I). This result (the increasing importance of X⋯X contacts when going from X = Cl to X = I) parallels the observations in the FdX2 sytems. In addition to the X⋯X inter­actions, C—H⋯X hydrogen bonds are important for all com­pounds, especially the chloro com­pound. π–π inter­actions are very strong for FdI4 (virtually no displacement of the Cp rings of different mol­ecules), while in FdCl4, the shift between the perpendicular projection of one centroid to the centroid of a neighbouring mol­ecule is quite substantial. In FdI3, C—H⋯π inter­actions seem to be of some importance, while in FcBr5, a weak C—Br⋯π inter­action can be observed.

Table 7
Characteristics of the X⋯X inter­actions in FdCl4, FdI3, FdI4 and FcBr5

  R—X⋯X′—R′ X⋯X (Å) Θ1 (°) Θ2 (°) |Θ1 − Θ2| (°) XB Type
FdI3 C1—I1⋯Br2—C2 3.74p 90.5 172.6 82.1 II
  C1—I1⋯I3—C6 3.728 174.4 115.1 59.3 II
FdI4 C1—I1⋯I3—C6 3.679 165.1 79.9 85.2 II
  C2—I2⋯I12—C12 3.933 159.6 97.1 62.5 II
  C6—I3⋯I13—C16 3.756 99.4 169.3 69.9 II
  C7—I4⋯I12—C12 3.823 83.0 165.8 82.8 II
  C11—I11⋯I13—C16 3.823 163.0 70.3 92.7 II
FdCl4 C11—Cl1⋯Cl2—C21 3.504 165.5 161.5 4.0 I
FcBr5 C2A—Br2A⋯Br3B—C3B 3.352 137.3 168.4 31.1 II
  C2B—Br2B⋯Br3B—C3B 3.656 164.7 123.2 41.5 II

4. Conclusion

Both stepwise deprotonation/electrophilic bromination starting from 1,1′,2,2′-tetra­bromo­ferrocene and permercuration/bromination of ferrocene lead to mixtures of polybrominated ferrocenes. However, by a combination of chromatography and recrystallization, it was possible to obtain crystals of hexa- and octa­bromo­ferrocene, as well as of nona­bromo(bromo­mer­cur­io)ferrocene. Hexa­bromo­ferrocene shows an eclipsed conformation of the Cp rings, as was also found for the already known structures of 1,1′-di­bromo- and 1,1′,2,2′-tetra­bromo­ferrocene. Ferrocenes with a higher bromine content apparently prefer a staggered conformation, as was observed before for nona- and deca­bromo­ferrocene. All three title com­pounds show a com­bination of halogen bonding with either hydrogen bonding or π–π inter­actions. Dispersion inter­actions appear to be stronger than electrostatic inter­actions.

Supporting information

CCDC references: 2210089; 2210088; 2210087

Crystal structure: contains datablocks compd_3, compd_5, compd_8, global. DOI: https://doi.org/10.1107/S205322962200955X/qw3001sup1.cif

Structure factors: contains datablock compd_3. DOI: https://doi.org/10.1107/S205322962200955X/qw3001compd_3sup2.hkl

Structure factors: contains datablock compd_5. DOI: https://doi.org/10.1107/S205322962200955X/qw3001compd_5sup3.hkl

Structure factors: contains datablock compd_8. DOI: https://doi.org/10.1107/S205322962200955X/qw3001compd_8sup4.hkl

Additional figures. DOI: https://doi.org/10.1107/S205322962200955X/qw3001sup5.pdf


Computing details top

Data collection: CrysAlis PRO (Agilent, 2014) for compd_3; APEX2 (Bruker, 2012) for compd_5, compd_8. Cell refinement: CrysAlis PRO (Agilent, 2014) for compd_3; APEX2 (Bruker, 2012) for compd_5, compd_8. Data reduction: CrysAlis PRO (Agilent, 2014) for compd_3; SAINT (Bruker, 2011) for compd_5, compd_8. Program(s) used to solve structure: SHELXT (Sheldrick, 2015a) for compd_3, compd_5; SHELXT2014 (Sheldrick, 2015a) for compd_8. For all structures, program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015b).

Bis(1,2,3-tribromocyclopentadienyl)iron(II) (compd_3) top
Crystal data top
[Fe(C5H2Br3)2]Z = 2
Mr = 656.69F(000) = 598
Triclinic, P1Dx = 3.079 Mg m−3
a = 7.0903 (3) ÅMo Kα radiation, λ = 0.71073 Å
b = 7.4318 (5) ÅCell parameters from 2222 reflections
c = 13.8071 (5) Åθ = 4.4–29.1°
α = 88.745 (4)°µ = 17.86 mm−1
β = 84.993 (3)°T = 153 K
γ = 77.728 (4)°Rod, yellow
V = 708.21 (6) Å30.49 × 0.15 × 0.05 mm
Data collection top
Agilent XCalibur 2
diffractometer		3234 independent reflections
Radiation source: Enhance (Mo) X-ray Source2496 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.041
Detector resolution: 15.9809 pixels mm-1θmax = 27.5°, θmin = 4.4°
ω scansh = −9→9
Absorption correction: multi-scan
(CrysAlis PRO; Agilent, 2014)		k = −9→9
Tmin = 0.434, Tmax = 1.000l = −17→17
9297 measured reflections
Refinement top
Refinement on F2Primary atom site location: dual
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.043H-atom parameters constrained
wR(F2) = 0.090 w = 1/[σ2(Fo2) + (0.0263P)2 + 2.1323P]
where P = (Fo2 + 2Fc2)/3
S = 1.09(Δ/σ)max = 0.001
3234 reflectionsΔρmax = 2.31 e Å−3
162 parametersΔρmin = −0.97 e Å−3
2 restraints
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
Br110.18791 (10)0.93782 (10)0.66385 (5)0.03293 (18)0.964
Br120.70467 (10)0.82612 (11)0.59801 (5)0.0373 (2)0.964
Br130.85028 (10)0.33022 (11)0.57625 (4)0.0392 (2)
Br210.28443 (10)0.90368 (10)0.92101 (5)0.03273 (18)0.962
Br220.80318 (10)0.77138 (11)0.86137 (5)0.03604 (18)
Br230.92650 (9)0.27609 (10)0.83466 (5)0.03364 (18)
Br140.434 (2)0.195 (3)0.6369 (13)0.035 (4)*0.036
Br240.468 (2)0.154 (3)0.8634 (13)0.034 (4)*0.038
Fe10.48302 (12)0.53419 (13)0.75694 (6)0.0237 (2)
C110.3423 (9)0.7001 (9)0.6536 (4)0.0261 (14)
H110.2643110.8201930.6632360.031*0.036
C120.5467 (9)0.6582 (9)0.6273 (4)0.0271 (15)
H120.6289800.7435530.6166560.033*0.036
C130.6018 (9)0.4628 (9)0.6202 (4)0.0284 (15)
C140.4345 (10)0.3851 (10)0.6407 (4)0.0326 (16)
H140.4305430.2582350.6394970.039*0.964
C150.2755 (10)0.5343 (10)0.6631 (4)0.0317 (16)
H150.1458280.5240530.6813420.038*
C210.4231 (8)0.6678 (9)0.8879 (4)0.0259 (14)
H210.3510210.7899820.8985730.031*0.038
C220.6274 (9)0.6154 (9)0.8647 (4)0.0237 (13)
C230.6743 (8)0.4208 (9)0.8548 (4)0.0233 (14)
C240.5032 (10)0.3515 (10)0.8713 (4)0.0332 (16)
H240.4935560.2261190.8689920.040*0.962
C250.3465 (9)0.5074 (10)0.8921 (4)0.0293 (15)
H250.2140460.5029750.9063350.035*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Br110.0307 (4)0.0358 (4)0.0253 (3)0.0076 (3)−0.0012 (3)0.0037 (3)
Br120.0340 (4)0.0432 (5)0.0328 (4)−0.0084 (3)0.0071 (3)0.0079 (3)
Br130.0371 (4)0.0508 (5)0.0200 (3)0.0122 (3)−0.0003 (3)−0.0041 (3)
Br210.0323 (4)0.0359 (4)0.0232 (3)0.0067 (3)0.0014 (3)−0.0041 (3)
Br220.0313 (4)0.0408 (4)0.0375 (4)−0.0107 (3)−0.0017 (3)−0.0080 (3)
Br230.0294 (4)0.0380 (4)0.0277 (3)0.0063 (3)−0.0045 (3)0.0020 (3)
Fe10.0240 (5)0.0314 (5)0.0143 (4)−0.0022 (4)−0.0029 (3)0.0016 (4)
C110.028 (3)0.031 (4)0.016 (3)0.002 (3)−0.003 (2)0.003 (3)
C120.031 (3)0.031 (4)0.016 (3)0.000 (3)−0.001 (3)−0.001 (3)
C130.032 (3)0.036 (4)0.015 (3)−0.002 (3)−0.004 (3)−0.003 (3)
C140.040 (4)0.038 (4)0.021 (3)−0.010 (3)−0.008 (3)−0.004 (3)
C150.030 (4)0.047 (5)0.021 (3)−0.014 (3)−0.009 (3)0.007 (3)
C210.019 (3)0.033 (4)0.021 (3)0.002 (3)0.001 (2)0.004 (3)
C220.023 (3)0.033 (4)0.015 (3)−0.005 (3)−0.003 (2)−0.001 (3)
C230.018 (3)0.037 (4)0.013 (3)−0.001 (3)−0.003 (2)0.001 (3)
C240.044 (4)0.037 (4)0.018 (3)−0.007 (3)−0.006 (3)0.006 (3)
C250.024 (3)0.045 (4)0.017 (3)−0.003 (3)−0.003 (2)0.002 (3)
Geometric parameters (Å, º) top
Br11—C111.871 (6)C11—C151.411 (9)
Br12—C121.862 (7)C11—C121.432 (9)
Br13—C131.883 (6)C11—H110.9500
Br21—C211.863 (6)C12—C131.424 (9)
Br22—C221.871 (7)C12—H120.9500
Br23—C231.881 (6)C13—C141.430 (9)
Br14—C141.41 (2)C14—C151.421 (9)
Br24—C241.55 (2)C14—H140.9500
Fe1—C132.033 (6)C15—H150.9500
Fe1—C232.039 (6)C21—C251.409 (9)
Fe1—C152.044 (6)C21—C221.427 (8)
Fe1—C222.048 (6)C21—H210.9500
Fe1—C112.049 (6)C22—C231.420 (9)
Fe1—C212.049 (6)C23—C241.415 (9)
Fe1—C252.052 (6)C24—C251.439 (9)
Fe1—C242.054 (6)C24—H240.9500
Fe1—C122.055 (6)C25—H250.9500
Fe1—C142.064 (6)
C13—Fe1—C23109.3 (2)C13—C12—H12126.9
C13—Fe1—C1568.3 (3)C11—C12—H12126.9
C23—Fe1—C15155.3 (3)Fe1—C12—H12126.5
C13—Fe1—C22124.8 (3)C12—C13—C14109.4 (6)
C23—Fe1—C2240.7 (2)C12—C13—Br13125.0 (5)
C15—Fe1—C22160.6 (3)C14—C13—Br13125.2 (5)
C13—Fe1—C1168.1 (2)C12—C13—Fe170.4 (3)
C23—Fe1—C11163.6 (3)C14—C13—Fe170.7 (4)
C15—Fe1—C1140.3 (3)Br13—C13—Fe1130.6 (3)
C22—Fe1—C11126.5 (3)Br14—C14—C15128.3 (8)
C13—Fe1—C21160.7 (3)Br14—C14—C13124.9 (8)
C23—Fe1—C2168.2 (2)C15—C14—C13106.8 (6)
C15—Fe1—C21122.3 (3)Br14—C14—Fe1128.2 (9)
C22—Fe1—C2140.8 (2)C15—C14—Fe169.0 (4)
C11—Fe1—C21108.6 (2)C13—C14—Fe168.4 (4)
C13—Fe1—C25158.4 (3)C15—C14—H14126.6
C23—Fe1—C2568.1 (2)C13—C14—H14126.6
C15—Fe1—C25104.6 (3)Fe1—C14—H14127.5
C22—Fe1—C2568.2 (2)C11—C15—C14108.6 (6)
C11—Fe1—C25120.6 (2)C11—C15—Fe170.0 (4)
C21—Fe1—C2540.2 (3)C14—C15—Fe170.5 (4)
C13—Fe1—C24122.9 (3)C11—C15—H15125.7
C23—Fe1—C2440.4 (3)C14—C15—H15125.7
C15—Fe1—C24118.6 (3)Fe1—C15—H15125.3
C22—Fe1—C2468.6 (3)C25—C21—C22108.3 (5)
C11—Fe1—C24155.0 (3)C25—C21—Br21125.3 (4)
C21—Fe1—C2468.5 (3)C22—C21—Br21126.0 (5)
C25—Fe1—C2441.0 (3)C25—C21—Fe170.0 (4)
C13—Fe1—C1240.8 (2)C22—C21—Fe169.5 (3)
C23—Fe1—C12126.6 (2)Br21—C21—Fe1131.4 (3)
C15—Fe1—C1268.8 (3)C25—C21—H21125.8
C22—Fe1—C12110.6 (3)C22—C21—H21125.8
C11—Fe1—C1240.8 (2)Fe1—C21—H21126.2
C21—Fe1—C12124.2 (3)C23—C22—C21107.3 (6)
C25—Fe1—C12157.7 (3)C23—C22—Br22126.3 (4)
C24—Fe1—C12161.0 (3)C21—C22—Br22126.1 (5)
C13—Fe1—C1440.9 (3)C23—C22—Fe169.3 (3)
C23—Fe1—C14121.4 (3)C21—C22—Fe169.7 (4)
C15—Fe1—C1440.5 (3)Br22—C22—Fe1131.0 (3)
C22—Fe1—C14158.8 (3)C24—C23—C22109.2 (5)
C11—Fe1—C1468.0 (3)C24—C23—Br23125.2 (5)
C21—Fe1—C14157.3 (3)C22—C23—Br23125.3 (5)
C25—Fe1—C14120.7 (3)C24—C23—Fe170.3 (3)
C24—Fe1—C14104.6 (3)C22—C23—Fe170.0 (3)
C12—Fe1—C1468.9 (3)Br23—C23—Fe1130.2 (3)
C15—C11—C12109.0 (6)C23—C24—C25106.8 (6)
C15—C11—Br11125.9 (5)C23—C24—Br24131.1 (8)
C12—C11—Br11124.9 (5)C25—C24—Br24121.9 (8)
C15—C11—Fe169.6 (3)C23—C24—Fe169.2 (4)
C12—C11—Fe169.8 (3)C25—C24—Fe169.4 (4)
Br11—C11—Fe1130.3 (3)Br24—C24—Fe1123.0 (7)
C15—C11—H11125.5C23—C24—H24126.6
C12—C11—H11125.5C25—C24—H24126.6
Fe1—C11—H11126.7Fe1—C24—H24126.3
C13—C12—C11106.2 (6)C21—C25—C24108.4 (6)
C13—C12—Br12126.8 (5)C21—C25—Fe169.8 (4)
C11—C12—Br12126.8 (5)C24—C25—Fe169.6 (3)
C13—C12—Fe168.8 (3)C21—C25—H25125.8
C11—C12—Fe169.4 (3)C24—C25—H25125.8
Br12—C12—Fe1130.2 (3)Fe1—C25—H25126.4
C15—C11—C12—C130.5 (6)C25—C21—C22—C230.1 (6)
Br11—C11—C12—C13−175.1 (4)Br21—C21—C22—C23173.6 (4)
Fe1—C11—C12—C1359.2 (4)Fe1—C21—C22—C23−59.4 (4)
C15—C11—C12—Br12175.8 (4)C25—C21—C22—Br22−173.9 (4)
Br11—C11—C12—Br120.3 (8)Br21—C21—C22—Br22−0.4 (8)
Fe1—C11—C12—Br12−125.4 (5)Fe1—C21—C22—Br22126.6 (5)
C15—C11—C12—Fe1−58.7 (4)C25—C21—C22—Fe159.5 (4)
Br11—C11—C12—Fe1125.7 (4)Br21—C21—C22—Fe1−127.0 (5)
C11—C12—C13—C140.7 (6)C21—C22—C23—C240.1 (6)
Br12—C12—C13—C14−174.7 (4)Br22—C22—C23—C24174.0 (4)
Fe1—C12—C13—C1460.2 (4)Fe1—C22—C23—C24−59.6 (4)
C11—C12—C13—Br13174.0 (4)C21—C22—C23—Br23−174.6 (4)
Br12—C12—C13—Br13−1.4 (8)Br22—C22—C23—Br23−0.7 (7)
Fe1—C12—C13—Br13−126.5 (4)Fe1—C22—C23—Br23125.7 (4)
C11—C12—C13—Fe1−59.6 (4)C21—C22—C23—Fe159.6 (4)
Br12—C12—C13—Fe1125.1 (5)Br22—C22—C23—Fe1−126.4 (4)
C12—C13—C14—Br14177.6 (11)C22—C23—C24—C25−0.1 (6)
Br13—C13—C14—Br144.3 (13)Br23—C23—C24—C25174.6 (4)
Fe1—C13—C14—Br14−122.3 (11)Fe1—C23—C24—C25−59.5 (4)
C12—C13—C14—C15−1.5 (7)C22—C23—C24—Br24175.6 (10)
Br13—C13—C14—C15−174.8 (4)Br23—C23—C24—Br24−9.7 (12)
Fe1—C13—C14—C1558.5 (4)Fe1—C23—C24—Br24116.2 (10)
C12—C13—C14—Fe1−60.0 (4)C22—C23—C24—Fe159.3 (4)
Br13—C13—C14—Fe1126.7 (5)Br23—C23—C24—Fe1−126.0 (4)
C12—C11—C15—C14−1.4 (7)C22—C21—C25—C24−0.1 (7)
Br11—C11—C15—C14174.1 (4)Br21—C21—C25—C24−173.7 (4)
Fe1—C11—C15—C14−60.2 (4)Fe1—C21—C25—C2459.0 (4)
C12—C11—C15—Fe158.8 (4)C22—C21—C25—Fe1−59.2 (4)
Br11—C11—C15—Fe1−125.7 (4)Br21—C21—C25—Fe1127.3 (5)
Br14—C14—C15—C11−177.3 (11)C23—C24—C25—C210.2 (6)
C13—C14—C15—C111.8 (7)Br24—C24—C25—C21−176.0 (9)
Fe1—C14—C15—C1159.9 (4)Fe1—C24—C25—C21−59.2 (4)
Br14—C14—C15—Fe1122.8 (12)C23—C24—C25—Fe159.4 (4)
C13—C14—C15—Fe1−58.2 (4)Br24—C24—C25—Fe1−116.8 (9)
Bis(1,2,3,4-tetrabromocyclopentadienyl)iron(II) (compd_5) top
Crystal data top
[Fe(C5HBr4)2]Z = 1
Mr = 817.25F(000) = 368
Triclinic, P1Dx = 3.461 Mg m−3
a = 6.9395 (2) ÅMo Kα radiation, λ = 0.71073 Å
b = 7.0548 (2) ÅCell parameters from 7252 reflections
c = 8.9271 (3) Åθ = 3.0–36.2°
α = 67.577 (1)°µ = 21.33 mm−1
β = 76.160 (1)°T = 103 K
γ = 86.461 (1)°Rod, yellow
V = 392.06 (2) Å30.03 × 0.01 × 0.01 mm
Data collection top
D8 Venture
diffractometer		3772 independent reflections
Radiation source: rotating anode generator3107 reflections with I > 2σ(I)
Detector resolution: 7.4074 pixels mm-1θmax = 36.3°, θmin = 3.0°
mix of ω and phi scansh = −11→11
Absorption correction: multi-scan
(TWINABS; Bruker, 2012)		k = −10→11
Tmin = 0.180, Tmax = 0.344l = 0→14
3772 measured reflections
Refinement top
Refinement on F2Primary atom site location: dual
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.037H-atom parameters constrained
wR(F2) = 0.076 w = 1/[σ2(Fo2) + (0.0237P)2 + 1.5954P]
where P = (Fo2 + 2Fc2)/3
S = 1.06(Δ/σ)max = 0.001
3772 reflectionsΔρmax = 1.32 e Å−3
89 parametersΔρmin = −1.31 e Å−3
0 restraints
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refined as a 2-component twin.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
C10.2630 (5)0.5035 (5)0.3994 (4)0.0110 (5)
C20.2568 (5)0.6705 (5)0.4545 (4)0.0100 (5)
C30.2493 (5)0.5846 (5)0.6289 (4)0.0095 (5)
C40.2505 (5)0.3669 (5)0.6804 (4)0.0094 (5)
C50.2606 (5)0.3150 (5)0.5389 (4)0.0094 (5)
H50.2649900.1808130.5375790.011*
Br10.26938 (5)0.52654 (6)0.18277 (4)0.01451 (7)
Br20.24350 (5)0.94767 (5)0.32428 (4)0.01363 (7)
Br30.22892 (5)0.73434 (5)0.76565 (4)0.01270 (7)
Br40.23435 (5)0.17894 (5)0.89794 (4)0.01490 (7)
Fe10.5000000.5000000.5000000.00706 (11)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0120 (12)0.0147 (14)0.0079 (12)0.0016 (10)−0.0035 (10)−0.0054 (11)
C20.0112 (11)0.0101 (13)0.0088 (12)0.0018 (10)−0.0030 (9)−0.0036 (10)
C30.0109 (12)0.0098 (13)0.0070 (12)−0.0002 (10)−0.0006 (9)−0.0033 (10)
C40.0099 (11)0.0095 (13)0.0076 (12)−0.0002 (9)−0.0010 (9)−0.0024 (10)
C50.0112 (12)0.0092 (13)0.0076 (12)0.0006 (10)−0.0019 (10)−0.0032 (10)
Br10.01640 (14)0.01897 (17)0.01080 (14)0.00160 (12)−0.00560 (11)−0.00720 (12)
Br20.01950 (15)0.00938 (14)0.01115 (14)0.00466 (11)−0.00569 (11)−0.00231 (11)
Br30.01718 (15)0.01280 (15)0.01024 (14)0.00378 (11)−0.00345 (11)−0.00702 (11)
Br40.01921 (15)0.01260 (15)0.00856 (14)−0.00057 (11)−0.00061 (11)−0.00070 (11)
Fe10.0084 (2)0.0070 (3)0.0056 (2)0.00118 (19)−0.0021 (2)−0.0021 (2)
Geometric parameters (Å, º) top
C1—C51.431 (5)C3—Br31.874 (3)
C1—C21.434 (5)C3—Fe12.036 (3)
C1—Br11.868 (3)C4—C51.429 (5)
C1—Fe12.048 (3)C4—Br41.869 (3)
C2—C31.427 (5)C4—Fe12.046 (3)
C2—Br21.865 (3)C5—Fe12.056 (3)
C2—Fe12.041 (3)C5—H50.9500
C3—C41.426 (5)
C5—C1—C2108.6 (3)C2i—Fe1—C4111.21 (13)
C5—C1—Br1125.4 (3)C2—Fe1—C468.79 (13)
C2—C1—Br1125.9 (2)C3i—Fe1—C4i40.88 (13)
C5—C1—Fe169.90 (18)C3—Fe1—C4i139.12 (13)
C2—C1—Fe169.19 (18)C2i—Fe1—C4i68.79 (13)
Br1—C1—Fe1127.49 (17)C2—Fe1—C4i111.21 (13)
C3—C2—C1107.5 (3)C4—Fe1—C4i180.0
C3—C2—Br2126.5 (2)C3i—Fe1—C1i68.80 (13)
C1—C2—Br2125.9 (2)C3—Fe1—C1i111.20 (13)
C3—C2—Fe169.33 (18)C2i—Fe1—C1i41.06 (14)
C1—C2—Fe169.75 (18)C2—Fe1—C1i138.94 (14)
Br2—C2—Fe1129.31 (17)C4—Fe1—C1i111.66 (13)
C4—C3—C2108.0 (3)C4i—Fe1—C1i68.34 (13)
C4—C3—Br3126.6 (2)C3i—Fe1—C1111.20 (13)
C2—C3—Br3125.3 (2)C3—Fe1—C168.80 (13)
C4—C3—Fe169.94 (18)C2i—Fe1—C1138.94 (14)
C2—C3—Fe169.68 (18)C2—Fe1—C141.06 (14)
Br3—C3—Fe1128.15 (17)C4—Fe1—C168.34 (13)
C3—C4—C5108.8 (3)C4i—Fe1—C1111.66 (13)
C3—C4—Br4125.8 (2)C1i—Fe1—C1180.00 (8)
C5—C4—Br4125.4 (2)C3i—Fe1—C5110.92 (12)
C3—C4—Fe169.18 (17)C3—Fe1—C569.08 (13)
C5—C4—Fe170.00 (17)C2i—Fe1—C5110.77 (13)
Br4—C4—Fe1128.05 (17)C2—Fe1—C569.23 (13)
C4—C5—C1107.1 (3)C4—Fe1—C540.76 (13)
C4—C5—Fe169.24 (18)C4i—Fe1—C5139.24 (13)
C1—C5—Fe169.29 (18)C1i—Fe1—C5139.19 (13)
C4—C5—H5126.5C1—Fe1—C540.81 (13)
C1—C5—H5126.5C3i—Fe1—C5i69.08 (13)
Fe1—C5—H5126.6C3—Fe1—C5i110.92 (13)
C3i—Fe1—C3180.0C2i—Fe1—C5i69.23 (13)
C3i—Fe1—C2i40.99 (13)C2—Fe1—C5i110.77 (13)
C3—Fe1—C2i139.01 (13)C4—Fe1—C5i139.24 (13)
C3i—Fe1—C2139.01 (13)C4i—Fe1—C5i40.76 (13)
C3—Fe1—C240.99 (13)C1i—Fe1—C5i40.81 (13)
C2i—Fe1—C2180.0C1—Fe1—C5i139.19 (13)
C3i—Fe1—C4139.12 (13)C5—Fe1—C5i180.0
C3—Fe1—C440.88 (13)
C5—C1—C2—C3−0.4 (4)Br3—C3—C4—C5177.8 (2)
Br1—C1—C2—C3178.8 (2)Fe1—C3—C4—C5−59.0 (2)
Fe1—C1—C2—C3−59.3 (2)C2—C3—C4—Br4−177.9 (2)
C5—C1—C2—Br2−176.6 (2)Br3—C3—C4—Br4−0.6 (4)
Br1—C1—C2—Br22.6 (4)Fe1—C3—C4—Br4122.6 (2)
Fe1—C1—C2—Br2124.5 (3)C2—C3—C4—Fe159.5 (2)
C5—C1—C2—Fe158.9 (2)Br3—C3—C4—Fe1−123.2 (3)
Br1—C1—C2—Fe1−121.9 (3)C3—C4—C5—C1−0.8 (4)
C1—C2—C3—C4−0.1 (4)Br4—C4—C5—C1177.7 (2)
Br2—C2—C3—C4176.1 (2)Fe1—C4—C5—C1−59.2 (2)
Fe1—C2—C3—C4−59.7 (2)C3—C4—C5—Fe158.5 (2)
C1—C2—C3—Br3−177.4 (2)Br4—C4—C5—Fe1−123.1 (2)
Br2—C2—C3—Br3−1.3 (4)C2—C1—C5—C40.7 (4)
Fe1—C2—C3—Br3123.0 (2)Br1—C1—C5—C4−178.5 (2)
C1—C2—C3—Fe159.6 (2)Fe1—C1—C5—C459.2 (2)
Br2—C2—C3—Fe1−124.3 (3)C2—C1—C5—Fe1−58.5 (2)
C2—C3—C4—C50.5 (4)Br1—C1—C5—Fe1122.4 (3)
Symmetry code: (i) −x+1, −y+1, −z+1.
(1-Bromomercurio-2,3,4,5-tetrabromocyclopentadienyl)(1,2,3,4,5-pentabromocyclopentadienyl)iron(II) (compd_8) top
Crystal data top
[FeHgBr(C5Br4)(C5Br5)]F(000) = 2064
Mr = 1175.64Dx = 3.893 Mg m−3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
a = 8.9784 (3) ÅCell parameters from 9571 reflections
b = 14.0971 (4) Åθ = 2.6–26.1°
c = 15.8485 (4) ŵ = 28.28 mm−1
β = 90.689 (1)°T = 295 K
V = 2005.79 (10) Å3Rod, yellow
Z = 40.06 × 0.02 × 0.02 mm
Data collection top
D8 Venture
diffractometer		4098 independent reflections
Radiation source: rotating anode generator3154 reflections with I > 2σ(I)
Detector resolution: 7.4074 pixels mm-1Rint = 0.050
mix of ω and phi scansθmax = 26.4°, θmin = 2.9°
Absorption correction: multi-scan
(SADABS; Krause et al., 2015)		h = −11→11
Tmin = 0.193, Tmax = 0.332k = −17→17
33353 measured reflectionsl = −19→19
Refinement top
Refinement on F20 restraints
Least-squares matrix: fullPrimary atom site location: dual
R[F2 > 2σ(F2)] = 0.036 w = 1/[σ2(Fo2) + (0.0321P)2 + 17.6846P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.092(Δ/σ)max = 0.001
S = 1.06Δρmax = 1.63 e Å−3
4098 reflectionsΔρmin = −1.24 e Å−3
199 parameters
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
C10.3728 (11)0.6144 (7)0.4691 (5)0.048 (2)
C20.3219 (10)0.5425 (6)0.4119 (6)0.046 (2)
C30.4378 (9)0.5238 (6)0.3545 (6)0.0386 (19)
C40.5618 (9)0.5838 (6)0.3754 (5)0.0376 (19)
C50.5205 (10)0.6401 (6)0.4451 (5)0.041 (2)
C60.1984 (9)0.7471 (6)0.3246 (5)0.0372 (19)
C70.2227 (9)0.6896 (6)0.2538 (5)0.0381 (19)
C80.3692 (10)0.7103 (6)0.2257 (5)0.0387 (19)
C90.4324 (9)0.7793 (6)0.2789 (5)0.0360 (18)
C100.3276 (9)0.8041 (6)0.3418 (5)0.0374 (19)
Br10.27025 (16)0.66542 (10)0.55928 (7)0.0828 (4)
Br20.13919 (12)0.48144 (10)0.41585 (10)0.0881 (5)
Br30.43841 (15)0.43142 (8)0.27139 (8)0.0744 (4)
Br40.74361 (11)0.58160 (8)0.32153 (8)0.0633 (3)
Br50.64199 (14)0.73095 (8)0.49869 (7)0.0657 (3)
Br60.02030 (11)0.75651 (8)0.38521 (7)0.0565 (3)
Br70.08463 (12)0.61035 (8)0.20025 (7)0.0584 (3)
Br80.45641 (13)0.65863 (9)0.12890 (6)0.0664 (3)
Br90.61817 (11)0.83682 (8)0.26468 (6)0.0561 (3)
Br100.30895 (15)1.00135 (9)0.56050 (8)0.0737 (3)
Fe10.37661 (12)0.66252 (8)0.34720 (7)0.0310 (2)
Hg10.33752 (4)0.89788 (3)0.44073 (2)0.04929 (13)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.055 (6)0.053 (6)0.035 (5)0.012 (5)0.013 (4)0.018 (4)
C20.038 (5)0.039 (5)0.061 (6)0.001 (4)0.000 (4)0.024 (4)
C30.038 (5)0.029 (4)0.049 (5)0.000 (4)−0.009 (4)0.000 (4)
C40.036 (4)0.035 (5)0.042 (5)0.001 (4)0.003 (4)0.002 (4)
C50.052 (5)0.037 (5)0.035 (4)0.003 (4)−0.007 (4)0.001 (4)
C60.037 (4)0.038 (5)0.037 (4)0.006 (4)0.000 (4)0.009 (4)
C70.042 (5)0.039 (5)0.033 (4)0.002 (4)−0.004 (4)0.006 (4)
C80.046 (5)0.040 (5)0.030 (4)0.002 (4)0.003 (4)0.002 (4)
C90.039 (5)0.035 (5)0.033 (4)−0.002 (4)0.001 (3)0.011 (4)
C100.042 (5)0.028 (4)0.042 (5)−0.001 (4)−0.003 (4)0.006 (4)
Br10.0975 (9)0.1086 (10)0.0430 (6)0.0443 (8)0.0300 (6)0.0162 (6)
Br20.0453 (6)0.0826 (9)0.1366 (12)−0.0178 (6)0.0029 (7)0.0531 (9)
Br30.0965 (9)0.0442 (6)0.0819 (8)0.0015 (6)−0.0275 (7)−0.0233 (6)
Br40.0380 (5)0.0672 (7)0.0849 (8)0.0044 (5)0.0131 (5)−0.0040 (6)
Br50.0853 (8)0.0504 (6)0.0606 (6)0.0006 (5)−0.0303 (6)−0.0166 (5)
Br60.0387 (5)0.0638 (6)0.0673 (6)0.0041 (4)0.0110 (5)0.0041 (5)
Br70.0510 (6)0.0672 (7)0.0566 (6)−0.0122 (5)−0.0081 (5)−0.0058 (5)
Br80.0728 (7)0.0840 (8)0.0426 (5)−0.0054 (6)0.0139 (5)−0.0096 (5)
Br90.0541 (6)0.0614 (6)0.0532 (6)−0.0209 (5)0.0129 (5)0.0008 (5)
Br100.0875 (9)0.0667 (7)0.0670 (7)−0.0043 (6)0.0120 (6)−0.0210 (6)
Fe10.0313 (6)0.0302 (6)0.0316 (6)0.0001 (5)0.0034 (4)0.0027 (5)
Hg10.0585 (2)0.0407 (2)0.0488 (2)−0.00033 (17)0.00521 (17)−0.00432 (17)
Geometric parameters (Å, º) top
C1—C51.431 (13)C6—C101.434 (12)
C1—C21.432 (14)C6—Br61.880 (8)
C1—Br11.855 (9)C6—Fe12.024 (8)
C1—Fe12.049 (8)C7—C81.424 (12)
C2—C31.415 (13)C7—Br71.866 (9)
C2—Br21.855 (9)C7—Fe12.048 (8)
C2—Fe12.041 (8)C8—C91.404 (12)
C3—C41.434 (11)C8—Br81.877 (8)
C3—Br31.852 (9)C8—Fe12.041 (8)
C3—Fe12.034 (8)C9—C101.422 (11)
C4—C51.413 (12)C9—Br91.870 (8)
C4—Br41.852 (8)C9—Fe12.037 (8)
C4—Fe12.044 (8)C10—Fe12.045 (8)
C5—Br51.879 (9)C10—Hg12.052 (9)
C5—Fe12.032 (8)Br10—Hg12.4101 (12)
C6—C71.403 (12)
C5—C1—C2107.5 (8)Br9—C9—Fe1129.8 (4)
C5—C1—Br1125.3 (8)C9—C10—C6105.6 (7)
C2—C1—Br1127.3 (7)C9—C10—Fe169.3 (5)
C5—C1—Fe168.9 (5)C6—C10—Fe168.6 (5)
C2—C1—Fe169.2 (5)C9—C10—Hg1132.1 (6)
Br1—C1—Fe1127.8 (5)C6—C10—Hg1122.3 (6)
C3—C2—C1107.9 (8)Fe1—C10—Hg1126.1 (4)
C3—C2—Br2126.4 (7)C6—Fe1—C5136.1 (3)
C1—C2—Br2125.6 (7)C6—Fe1—C3142.1 (3)
C3—C2—Fe169.4 (5)C5—Fe1—C368.8 (3)
C1—C2—Fe169.8 (5)C6—Fe1—C968.2 (3)
Br2—C2—Fe1128.3 (5)C5—Fe1—C9111.9 (4)
C2—C3—C4108.4 (8)C3—Fe1—C9137.7 (4)
C2—C3—Br3126.6 (7)C6—Fe1—C867.8 (3)
C4—C3—Br3124.8 (6)C5—Fe1—C8141.7 (4)
C2—C3—Fe169.9 (5)C3—Fe1—C8112.1 (3)
C4—C3—Fe169.8 (5)C9—Fe1—C840.3 (3)
Br3—C3—Fe1129.7 (5)C6—Fe1—C2112.5 (3)
C5—C4—C3107.6 (7)C5—Fe1—C269.0 (4)
C5—C4—Br4127.6 (7)C3—Fe1—C240.6 (4)
C3—C4—Br4124.7 (6)C9—Fe1—C2177.9 (4)
C5—C4—Fe169.3 (5)C8—Fe1—C2137.9 (4)
C3—C4—Fe169.1 (5)C6—Fe1—C4176.2 (4)
Br4—C4—Fe1128.9 (4)C5—Fe1—C440.6 (3)
C4—C5—C1108.6 (8)C3—Fe1—C441.2 (3)
C4—C5—Br5125.5 (7)C9—Fe1—C4110.5 (3)
C1—C5—Br5126.0 (7)C8—Fe1—C4113.7 (3)
C4—C5—Fe170.2 (5)C2—Fe1—C468.9 (3)
C1—C5—Fe170.1 (5)C6—Fe1—C1041.3 (3)
Br5—C5—Fe1126.8 (5)C5—Fe1—C10108.6 (3)
C7—C6—C10110.0 (7)C3—Fe1—C10176.6 (3)
C7—C6—Br6126.2 (7)C9—Fe1—C1040.8 (3)
C10—C6—Br6123.7 (6)C8—Fe1—C1068.5 (3)
C7—C6—Fe170.8 (5)C2—Fe1—C10141.0 (4)
C10—C6—Fe170.2 (5)C4—Fe1—C10135.5 (3)
Br6—C6—Fe1128.8 (4)C6—Fe1—C740.3 (3)
C6—C7—C8106.6 (7)C5—Fe1—C7176.3 (4)
C6—C7—Br7126.9 (6)C3—Fe1—C7113.6 (3)
C8—C7—Br7126.2 (6)C9—Fe1—C768.5 (3)
C6—C7—Fe168.9 (5)C8—Fe1—C740.8 (3)
C8—C7—Fe169.3 (5)C2—Fe1—C7110.7 (4)
Br7—C7—Fe1131.0 (5)C4—Fe1—C7143.0 (3)
C9—C8—C7108.8 (7)C10—Fe1—C769.2 (3)
C9—C8—Br8126.2 (6)C6—Fe1—C1109.9 (3)
C7—C8—Br8124.9 (6)C5—Fe1—C141.0 (4)
C9—C8—Fe169.7 (5)C3—Fe1—C168.6 (4)
C7—C8—Fe169.9 (5)C9—Fe1—C1140.9 (4)
Br8—C8—Fe1129.4 (5)C8—Fe1—C1177.2 (4)
C8—C9—C10109.0 (7)C2—Fe1—C141.0 (4)
C8—C9—Br9125.6 (6)C4—Fe1—C168.7 (3)
C10—C9—Br9125.2 (6)C10—Fe1—C1110.9 (4)
C8—C9—Fe170.0 (5)C7—Fe1—C1136.4 (4)
C10—C9—Fe169.9 (5)C10—Hg1—Br10171.0 (2)
Overview of CSD structures of polyhaloferrocenes substituted on both rings top
Chemical formulaAbbreviation in this textRefcode in the CSDConformationReference
C10H8F2FeFdF2RACROFEclipsed, IInkpen et al. (2015)
C10H8Cl2FeFdCl2DUTSUH, DUTSUH01Eclipsed, IBryan & Leadbetter (1986); Inkpen et al. (2015)
C10H8Br2FeFdBr2BIPDOUEclipsed, IHnetinka et al. (2004)
C10H8I2FeFdI2KOPFAYStaggeredRoemer & Nijhuis (2014)
C10H7Br3FeFdBr3UTOBIRNearly eclipsed, VIButler et al. (2021)
C10H7I3FeFdI3EZAWUANearly eclipsed, VIEvans et al. (2021)
C10H6Cl4FeFdCl4CEVBEKEclipsed, IVSato et al. (1984)
C10H6Br4FeFdBr4UTOBUDEclipsed, IVButler et al. (2021)
C10H6I4Fe-FdI4ezawouEclipsed, VIEvans et al., 2021
C10H4Cl6FeFdCl6DUTSUGNo data in CSDBryan & Leadbetter (1986)
C10HBr9FeFdBr9FEFZAVStaggeredRupf et al. (2022)
C10Br10FeFdBr10FEFYUOstaggeredRupf et al. (2022)
Important geometrical parameters of compounds 3, 5 and 8 in comparison with literature data of closely related compounds top
CompoundC—Br (Å)Fe—C (Å)Fe—Ct (Å)Ct—Fe—Ct' (°)Br—Ct—Ct'—Br' (°)δ (Br—Cp) (Å)Reference
FdBr21.882 (4)/1.866 (4)2.035 (4)–2.054 (4)1.6500 (5)/1.6483 (5)177.71 (4)1.55 (1)0.137 (6)/0.082 (6)A
11.873 (2)–1.877 (2)2.036 (2)–2.052 (2)1.6482 (8)177.75 (6)1.59 (8)0.130 (1)–0.149 (1))B
31.863 (8)–1.880 (7)2.032 (7)–2.076 (8)1.653 (3)/1.654 (3)176.3 (2)2.09–2.380.123 (1)–0.168 (1)This work
51.865 (4)–1.873 (4)2.036 (4)–2.057 (4)1.6449 (16)18035.9–36.20.037 (1)–0.096 (1)This work
61.861 (10)–1.888 (11)2.02 (1)–2.06 (1)1.637 (1)/1.642 (1)178.5 (3)33.4 (5)0.005 (1)–0.146 (1)C
71.863 (4)–1.874 (4)2.041 (4)–2.049 (4)1.645 (2)18033.8 (2)0.085 (1)–0.142 (1)C
81.852 (9)–1.880 (8)2.024 (8)–2.049 (8)1.641 (4)/1.644 (4)178.4 (7)30.5 (1)–31.6 (1)0.004 (14)–0.142 (13)This work
8+AsF61.845 (8)–1.865 (8)2.066 (8)–2.116 (8)1.703 (4)/1.708 (4)178.9 (5)32.5 (4)-0.056 (1)–0.062 (1)C
FdBr2 is 1,1'-dibromoferrocene. `Ct' is the abbreviation for `centroid' of the Cp rings, as calculated by the corresponding feature in PLATON (Spek, 2020); δ (Br—Cp) is the distance of the Br atoms from the Cp plane. References: (A) Hnetinka et al. (2004); (B) Butler et al. (2021); (C) Rupf et al. (2022).
Individual contributions of the different interactions present in the crystal structures of FdBr2, 3, 5 and 8 top
CompoundC—HC—BrC—CH—HH—BrBr—BrHg—Br
FdBr2*17.13.7037.339.62.3–
1**6.21.66.014.252.419.6–
33.34.05.90.848.038.2–
51.26.85.90.920.964.3
8–10.73.5––77.78.2
Notes: (*) taken from: Shimizu & Ferreira da Silva (2018); (**) calculated from the downloaded CIF file, available from the CCDC as CSD refcode UTOBUB.
Hydrogen-bond parameters (Å, °) in compounds 3 and 5 top
CompoundD—H···AD—H (Å)H···A (Å)D···A (Å)D—H···A (°)
3C24—H24···Br21i0.953.103.965 (9)151.8
C25—H25···Br23ii0.953.133.874136.5
C14—H14···Br11i0.953.204.046 (9)149.8
C15—H15···Br13ii0.953.243.927 (8)131.8
5C5—H5···Br2i0.952.9853.786142.93
C5—H5···Br3i0.953.0153.809141.91
Symmetry codes: (i) x, y-1, z; (ii) x-1, y, z.
Characteristics of the Br···Br interactions found in compounds 1, 3, 5 and 8 and FdBr2 top
CompoundR—Br···Br'—R'Br···Br (Å)Θ1 (°)Θ2 (°)|Θ1 – Θ2| (°)XB Type
FdBr2*C1—Br1···Br2—C63.58689.7153.163.2II
1**C1—Br1···Br2—C23.564145.2156.411.2I
3C13—Br13···Br11—C113.617135.2153.818.6Quasi-Type I/Type II
C23—Br23···Br11—C113.582137.3143.36.0I
C23—Br23···Br21—C213.594146.9141.85.1I
C13—Br13···Br23—C233.65684.785.10.4IV
C11—Br11···Br21—C213.65785.284.40.8IV
5C1—Br1···Br3—C33.518160.8124.836.0II
C2—Br2···Br4—C43.538128.9163.834.9II
8C1—Br1···Br9—C93.545154.8117.437.4II
C4—Br4···Br6—C63.634117.7113.14.6I
C4—Br4···Br7—C73.657171.4112.558.9II
C3—Br3···Br6—C63.521174.165.9108.2II
C7—Br7···Br10—Hg13.658167.097.969.1II
C9—Br9···Br10—Hg13.642109.4163.454.0II
Notes: (*) taken from Shimizu & Ferreira da Silva (2018); (**) calculated from the downloaded CIF file, available from the CCDC as CSD refcode UTOBUB.
Characteristics of the X···X interactions in FdCl4, FdI3, FdI4 and FcBr5 top
CompoundR—X···X'—R'X···X (Å)Θ1 (°)Θ2 (°)|Θ1 – Θ2| (°)XB Type
FdI3C1—I1···Br2—C23.74p90.5172.682.1II
C1—I1···I3—C63.728174.4115.159.3II
FdI4C1—I1···I3—C63.679165.179.985.2II
C2—I2···I12—C123.933159.697.162.5II
C6—I3···I13—C163.75699.4169.369.9II
C7—I4···I12—C123.82383.0165.882.8II
C11—I11···I13—C163.823163.070.392.7II
FdCl4C11—Cl1···Cl2—C213.504165.5161.54.0I
FcBr5C2A—Br2A···Br3B—C3B3.352137.3168.431.1II
C2B—Br2B···Br3B—C3B3.656164.7123.241.5II
 

Acknowledgements

Open access funding enabled and organized by Projekt DEAL.

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Journal logoSTRUCTURAL
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ISSN: 2053-2296
Volume 78| Part 11| November 2022| Pages 578-590
https://doi.org/10.1107/S205322962200955X
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