metal-organic compounds
mer-Triiodotripyridineindium(III)
aInorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, England, and bDepartment of Chemistry, University of Exeter, Stocker Road, Exeter EX4 4QD, England
*Correspondence e-mail: tony.downs@chem.ox.ac.uk
Crystals of the title compound, [InI3(C5H5N)3], consist of discrete molecules lying on a twofold axis running parallel to the crystallographic b axis. The molecules exhibit meridional octahedral stereochemistry, with In—I bond lengths of 2.8390 (6) and 2.8676 (3) Å, and In—N bond lengths of 2.323 (5) and 2.309 (4) Å.
Comment
In an attempt to extend the chemistry of subvalent indium compounds, we have been investigating the feasibility of producing solutions in which an indium(I) halide is acceptably stable to e.g. toluene or toluene/ether), followed by warming of the mixture to see whether a solution of practical use in synthesis can be formed. Although ready dissolution without is rare, indium(I) iodide has proved to be the halide most prone to dissolve in organic solvents, of which pyridine or pyridine-containing mixtures have been among the most promising. Solutions of indium(I) iodide in a pyridine/m-xylene (2:1) mixture are lastingly stable below 243 K but undergo slow at room temperature, giving a mixture of indium metal and triiodotripyridineindium(III), (I). Crystallographic studies of (I) at 150 K have afforded a rare structural characterization of a neutral six-coordinate indium(III) iodide complex.
at temperatures between 190 and 300 K. One strategy has involved co-condensation of the vapours of the halide and an excess of a potential solvent (The orthorhombic crystals of (I) (Fig. 1) consist of neutral molecules with indium in a pseudo-octahedral environment and with the meridional stereochemistry suggested in a preliminary report (Small & Worrall, 1982) but different from that deduced on the basis of IR measurements (Adams et al., 1968). Unlike the corresponding chloride (Jeffs et al., 1984) and bromide (Small & Worrall, 1982) adducts, the iodo compound takes up no additional pyridine molecules of solvation, presumably as a result of the extra bulk of the iodide ligands.
The In—I bond lengths [2.8390 (6) and 2.8676 (3) Å] are comparable to those found in the related complex [InI3(4-MeC5H4N)3], (II) [2.803 (4), 2.848 (4) and 2.893 (4) Å; Brown & Tuck, 1996], there being a less pronounced but still distinct shortening of the unique In—I bond trans to a pyridine ring. For these two neutral six-coordinate InI3 complexes, the In—I distances occur in the range 2.80–2.90 Å. As expected, the corresponding distances are shorter in similar five-coordinate complexes (2.66–2.80 Å), and shorter still in four-coordinate complexes (2.50–2.74 Å), as revealed by the 19 hits in a search of the Cambridge Structural Database (Version 5.26; Allen, 2002). The terminal and bridging In—I distances of the In2I6 molecules of solid indium(III) iodide are 2.644 (2) and 2.842 (2) Å, respectively (Kniep et al., 1982).
The In—N bond lengths in (I), with an average of 2.316 Å, are not significantly different from those in (II) (2.31 Å), [InCl3(C5H5N)3]·C5H5N (2.327 Å) and [InBr3(C5H5N)3]·C5H5N (2.30 Å). In every case, the longest In—N bond is that trans to a halogen, viz. 2.323 (5) versus 2.309 (4) Å in (I), 2.34 (2) versus 2.28 (3)/2.30 (3) Å in (II), 2.377 (21) versus 2.302 (7) Å in [InCl3(C5H5N)3]·C5H5N and 2.32 (2) versus 2.28 (3)/2.31 (2) Å in [InBr3(C5H5N)3]·C5H5N, even if the difference is not always statistically significant. Any systematic dependence on the nature of the halogen is, at best, small, although no strict comparison can be made in view of the diversity of the data (most of which relate to crystals at room temperature).
The molecules in (I) each lie on a twofold rotation axis running through the I2—In—N2 group and parallel to the crystallographic b axis. As in (II), the I1—In—I1i and N1—In—N1i angles (symmetry code as in Table 1) depart from linearity, and each pyridine ring is tilted out of the appropriate plane by an average of 40 (2)°, in keeping with both the stronger non-bonded repulsion exerted by atom I2, as compared with N2, and minimization of the interaction between the iodide and pyridine functions. Analysis of the dimensions of the coordinated pyridine molecules indicate no unusual features. The packing of the molecules of (I) (Fig. 2) gives little evidence of specific interactions. At 3.17 Å, for example, the shortest H⋯I distance is consistent with a normal van der Waals contact, although the existence of weak hydrogen bonding is not precluded (Table 2). Likewise, short I⋯I contacts are evidently disfavoured (there are none below 5 Å), which could imply that the I atoms carry a substantial negative charge.
Experimental
Crystals of (I) were grown from a solution initially containing InI in pyridine/m-xylene (2:1) over a period of one month at room temperature.
Crystal data
|
Refinement
H atoms were positioned geometrically and treated using a riding model, with C—H distances assumed to be 1.00 Å. The Uiso(H) values were taken to be 1.2Ueq(C).
Data collection: COLLECT (Nonius, 2000); cell DENZO (Otwinowski & Minor, 1997); data reduction: DENZO; program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: CRYSTALS; software used to prepare material for publication: CRYSTALS.
Supporting information
10.1107/S0108270105006360/jz1705sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock . DOI: 10.1107/S0108270105006360/jz1705Isup2.hkl
Crystals of (I) were grown from a solution initially containing InI in pyridine/m-xylene (2:1) over a period of one month at room temperature.
H atoms were positioned geometrically and refined using a riding model, with C—H distances assumed to be 1.00 Å. The Uiso(H) values were taken to be 1.2Ueq(C). A three-term Chebychev polynomial weighting scheme was applied.
Data collection: Collect (Nonius, 2000); cell
DENZO (Otwinowski & Minor, 1997); data reduction: DENZO; program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: CRYSTALS; software used to prepare material for publication: CRYSTALS.Fig. 1. The molecular structure of (I), showing the atom-labelling scheme (ORTEPIII; Burnett & Johnson, 1996). Displacement ellipsoids are drawn at the 40% probability level. | |
Fig. 2. A packing diagram of (I), viewed along the a axis, with the b axis aligned vertically. Dotted lines indicate relatively short H···I distances, which may be indicative of weak hydrogen bonding. In atoms: horizontally hatched; I atoms: vertically hatched; N, C and H atoms: white. |
[InI3(C5H5N)3] | Dx = 2.415 Mg m−3 |
Mr = 732.84 | Mo Kα radiation, λ = 0.71073 Å |
Orthorhombic, Pbcn | Cell parameters from 13983 reflections |
a = 9.6622 (2) Å | θ = 5–28° |
b = 14.9139 (4) Å | µ = 5.77 mm−1 |
c = 13.9850 (4) Å | T = 150 K |
V = 2015.25 (9) Å3 | Block, colourless |
Z = 4 | 0.11 × 0.09 × 0.06 mm |
F(000) = 1336 |
Nonius KappaCCD diffractometer | 1670 reflections with I > 3.00u(I) |
Graphite monochromator | Rint = 0.038 |
ω scans | θmax = 27.5°, θmin = 5.1° |
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997) | h = −12→12 |
Tmin = 0.53, Tmax = 0.71 | k = −19→19 |
13983 measured reflections | l = −18→18 |
2293 independent reflections |
Refinement on F | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.025 | H-atom parameters constrained |
wR(F2) = 0.029 | Method, part 1, Chebychev polynomial, (Watkin, 1994, Prince, 1982) [weight] = 1.0/[A0*T0(x) + A1*T1(x) ··· + An-1]*Tn-1(x)] where Ai are the Chebychev coefficients listed below and x = F /Fmax Method = Robust Weighting (Prince, 1982) W = [weight] * [1-(ΔF/6*σF)2]2 Ai are: 0.403 0.231 0.196 |
S = 1.02 | (Δ/σ)max = 0.006 |
1670 reflections | Δρmax = 0.60 e Å−3 |
102 parameters | Δρmin = −0.86 e Å−3 |
0 restraints |
[InI3(C5H5N)3] | V = 2015.25 (9) Å3 |
Mr = 732.84 | Z = 4 |
Orthorhombic, Pbcn | Mo Kα radiation |
a = 9.6622 (2) Å | µ = 5.77 mm−1 |
b = 14.9139 (4) Å | T = 150 K |
c = 13.9850 (4) Å | 0.11 × 0.09 × 0.06 mm |
Nonius KappaCCD diffractometer | 2293 independent reflections |
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997) | 1670 reflections with I > 3.00u(I) |
Tmin = 0.53, Tmax = 0.71 | Rint = 0.038 |
13983 measured reflections |
R[F2 > 2σ(F2)] = 0.025 | 0 restraints |
wR(F2) = 0.029 | H-atom parameters constrained |
S = 1.02 | Δρmax = 0.60 e Å−3 |
1670 reflections | Δρmin = −0.86 e Å−3 |
102 parameters |
Experimental. Crystal cooling was performed with an Oxford Cryosystems CRYOSTREAM unit. |
x | y | z | Uiso*/Ueq | ||
In1 | 0.5000 | 0.38825 (2) | 0.7500 | 0.0176 | |
I1 | 0.68422 (3) | 0.399859 (18) | 0.589709 (18) | 0.0239 | |
I2 | 0.5000 | 0.19789 (2) | 0.7500 | 0.0299 | |
N1 | 0.3136 (4) | 0.3984 (2) | 0.6472 (2) | 0.0213 | |
C1 | 0.3117 (5) | 0.3478 (3) | 0.5668 (3) | 0.0245 | |
C2 | 0.1983 (5) | 0.3459 (3) | 0.5060 (3) | 0.0278 | |
C3 | 0.0823 (5) | 0.3948 (3) | 0.5306 (3) | 0.0294 | |
C4 | 0.0835 (5) | 0.4470 (4) | 0.6123 (3) | 0.0287 | |
C5 | 0.2020 (5) | 0.4477 (3) | 0.6682 (3) | 0.0242 | |
N2 | 0.5000 | 0.5440 (3) | 0.7500 | 0.0209 | |
C6 | 0.4785 (5) | 0.5902 (3) | 0.6688 (3) | 0.0262 | |
C7 | 0.4761 (6) | 0.6827 (3) | 0.6668 (4) | 0.0373 | |
C8 | 0.5000 | 0.7304 (4) | 0.7500 | 0.0404 | |
H11 | 0.3946 | 0.3107 | 0.5507 | 0.0294* | |
H21 | 0.2006 | 0.3099 | 0.4457 | 0.0334* | |
H31 | −0.0023 | 0.3925 | 0.4895 | 0.0352* | |
H41 | 0.0009 | 0.4835 | 0.6306 | 0.0344* | |
H51 | 0.2040 | 0.4865 | 0.7265 | 0.0290* | |
H61 | 0.4638 | 0.5564 | 0.6079 | 0.0315* | |
H71 | 0.4571 | 0.7151 | 0.6055 | 0.0448* | |
H81 | 0.5000 | 0.7974 | 0.7500 | 0.0485* |
U11 | U22 | U33 | U12 | U13 | U23 | |
In1 | 0.01875 (19) | 0.01875 (19) | 0.01533 (19) | 0.0000 | −0.00157 (15) | 0.0000 |
I1 | 0.02398 (15) | 0.02873 (15) | 0.01895 (14) | −0.00281 (11) | 0.00273 (11) | −0.00098 (11) |
I2 | 0.0435 (3) | 0.0190 (2) | 0.0272 (2) | 0.0000 | 0.00680 (19) | 0.0000 |
N1 | 0.0198 (17) | 0.0272 (19) | 0.0168 (15) | −0.0005 (15) | −0.0008 (14) | 0.0016 (14) |
C1 | 0.028 (2) | 0.026 (2) | 0.0197 (19) | −0.0001 (18) | −0.0068 (18) | −0.0026 (16) |
C2 | 0.036 (3) | 0.023 (2) | 0.025 (2) | −0.006 (2) | −0.0053 (19) | 0.0015 (17) |
C3 | 0.027 (2) | 0.032 (2) | 0.029 (2) | −0.0053 (19) | −0.0107 (19) | 0.010 (2) |
C4 | 0.022 (2) | 0.038 (3) | 0.026 (2) | 0.0047 (19) | −0.0029 (19) | 0.0094 (19) |
C5 | 0.022 (2) | 0.025 (2) | 0.026 (2) | 0.0025 (17) | −0.0033 (18) | 0.0070 (17) |
N2 | 0.025 (2) | 0.018 (2) | 0.020 (2) | 0.0000 | −0.006 (2) | 0.0000 |
C6 | 0.032 (3) | 0.027 (2) | 0.020 (2) | 0.0027 (18) | −0.0077 (18) | 0.0032 (18) |
C7 | 0.062 (4) | 0.022 (2) | 0.029 (3) | 0.007 (2) | −0.008 (2) | 0.0059 (19) |
C8 | 0.068 (5) | 0.019 (3) | 0.034 (4) | 0.0000 | −0.008 (4) | 0.0000 |
In1—I1 | 2.8676 (3) | C3—C4 | 1.382 (7) |
In1—I1i | 2.8676 (3) | C3—H31 | 1.000 |
In1—I2 | 2.8390 (6) | C4—C5 | 1.386 (6) |
In1—N1 | 2.309 (4) | C4—H41 | 1.000 |
In1—N1i | 2.309 (4) | C5—H51 | 1.000 |
In1—N2 | 2.323 (5) | N2—C6 | 1.343 (5) |
N1—C1 | 1.354 (5) | N2—C6i | 1.343 (5) |
N1—C5 | 1.338 (6) | C6—C7 | 1.381 (6) |
C1—C2 | 1.387 (6) | C6—H61 | 1.000 |
C1—H11 | 1.000 | C7—C8 | 1.383 (6) |
C2—C3 | 1.381 (7) | C7—H71 | 1.000 |
C2—H21 | 1.000 | C8—H81 | 1.000 |
I1—In1—I1i | 173.079 (18) | C3—C2—H21 | 120.728 |
I1—In1—I2 | 93.460 (9) | C2—C3—C4 | 119.7 (4) |
I1i—In1—I2 | 93.460 (9) | C2—C3—H31 | 120.138 |
I1—In1—N1 | 89.64 (9) | C4—C3—H31 | 120.137 |
I1i—In1—N1 | 89.91 (9) | C3—C4—C5 | 118.5 (4) |
I2—In1—N1 | 93.74 (9) | C3—C4—H41 | 120.729 |
I1—In1—N1i | 89.91 (9) | C5—C4—H41 | 120.730 |
I1i—In1—N1i | 89.64 (9) | N1—C5—C4 | 122.5 (4) |
I2—In1—N1i | 93.74 (9) | N1—C5—H51 | 118.738 |
N1—In1—N1i | 172.52 (18) | C4—C5—H51 | 118.738 |
I1—In1—N2 | 86.540 (9) | In1—N2—C6 | 120.8 (3) |
I1i—In1—N2 | 86.540 (9) | In1—N2—C6i | 120.8 (3) |
I2—In1—N2 | 179.995 | C6—N2—C6i | 118.4 (5) |
N1—In1—N2 | 86.26 (9) | N2—C6—C7 | 122.2 (4) |
N1i—In1—N2 | 86.26 (9) | N2—C6—H61 | 118.910 |
In1—N1—C1 | 119.4 (3) | C7—C6—H61 | 118.910 |
In1—N1—C5 | 121.9 (3) | C6—C7—C8 | 119.5 (5) |
C1—N1—C5 | 118.5 (4) | C6—C7—H71 | 120.229 |
N1—C1—C2 | 122.1 (4) | C8—C7—H71 | 120.227 |
N1—C1—H11 | 118.954 | C7—C8—C7i | 118.2 (6) |
C2—C1—H11 | 118.955 | C7—C8—H81 | 120.918 |
C1—C2—C3 | 118.5 (4) | C7i—C8—H81 | 120.918 |
C1—C2—H21 | 120.729 |
Symmetry code: (i) −x+1, y, −z+3/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
C2—H21···I1ii | 1.00 | 3.17 | 3.904 (5) | 131 |
C6—H61···I1iii | 1.00 | 3.18 | 3.946 (4) | 135 |
Symmetry codes: (ii) x−1/2, −y+1/2, −z+1; (iii) −x+1, −y+1, −z+1. |
Experimental details
Crystal data | |
Chemical formula | [InI3(C5H5N)3] |
Mr | 732.84 |
Crystal system, space group | Orthorhombic, Pbcn |
Temperature (K) | 150 |
a, b, c (Å) | 9.6622 (2), 14.9139 (4), 13.9850 (4) |
V (Å3) | 2015.25 (9) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 5.77 |
Crystal size (mm) | 0.11 × 0.09 × 0.06 |
Data collection | |
Diffractometer | Nonius KappaCCD diffractometer |
Absorption correction | Multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997) |
Tmin, Tmax | 0.53, 0.71 |
No. of measured, independent and observed [I > 3.00u(I)] reflections | 13983, 2293, 1670 |
Rint | 0.038 |
(sin θ/λ)max (Å−1) | 0.649 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.025, 0.029, 1.02 |
No. of reflections | 1670 |
No. of parameters | 102 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.60, −0.86 |
Computer programs: Collect (Nonius, 2000), DENZO (Otwinowski & Minor, 1997), DENZO, SIR92 (Altomare et al., 1994), CRYSTALS (Betteridge et al., 2003), CRYSTALS.
In1—I1 | 2.8676 (3) | In1—N1 | 2.309 (4) |
In1—I2 | 2.8390 (6) | In1—N2 | 2.323 (5) |
I1—In1—I1i | 173.079 (18) | N1—In1—N1i | 172.52 (18) |
I1—In1—I2 | 93.460 (9) | I1—In1—N2 | 86.540 (9) |
I1—In1—N1 | 89.64 (9) | I2—In1—N2 | 179.995 |
I2—In1—N1 | 93.74 (9) | N1—In1—N2 | 86.26 (9) |
I1—In1—N1i | 89.91 (9) |
Symmetry code: (i) −x+1, y, −z+3/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
C2—H21···I1ii | 1.00 | 3.17 | 3.904 (5) | 131 |
C6—H61···I1iii | 1.00 | 3.18 | 3.946 (4) | 135 |
Symmetry codes: (ii) x−1/2, −y+1/2, −z+1; (iii) −x+1, −y+1, −z+1. |
Acknowledgements
The authors thank the EPSRC for the award of a research grant including the funding of a postdoctoral assistantship for JAJP.
References
Adams, D. M., Carty, A. J., Carty, P. & Tuck, D. G. (1968). J. Chem. Soc. A, pp. 162–164. CrossRef Google Scholar
Allen, F. H. (2002). Acta Cryst. B58, 380–388. Web of Science CrossRef CAS IUCr Journals Google Scholar
Altomare, A., Cascarano, G., Giacovazzo, C., Guagliardi, A., Burla, M. C., Polidori, G. & Camalli, M. (1994). J. Appl. Cryst. 27, 435. CrossRef Web of Science IUCr Journals Google Scholar
Betteridge, P. W., Carruthers, J. R., Cooper, R. I., Prout, K. & Watkin, D. J. (2003). J. Appl. Cryst. 36, 1487. Web of Science CrossRef IUCr Journals Google Scholar
Brown, M. A. & Tuck, D. G. (1996). Inorg. Chim. Acta, 247, 135–138. CSD CrossRef CAS Web of Science Google Scholar
Burnett, M. N. & Johnson, C. K. (1996). ORTEPIII. Report ORNL-6895. Oak Ridge National Laboratory, Tennessee, USA. Google Scholar
Jeffs, S. E., Small, R. W. H. & Worrall, I. J. (1984). Acta Cryst. C40, 1329–1331. CSD CrossRef CAS Web of Science IUCr Journals Google Scholar
Kniep, R., Blees, P. & Poll, W. (1982). Angew. Chem. Int. Ed. Engl. 21, 386. CrossRef Web of Science Google Scholar
Nonius (2000). COLLECT. Nonius BV, Delft, The Netherlands. Google Scholar
Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307–326. New York: Academic Press. Google Scholar
Prince, E. (1982). Mathematical Techniques in Crystallography and Materials Science. New York: Springer-Verlag. Google Scholar
Small, R. W. H. & Worrall, I. J. (1982). Acta Cryst. B38, 932–934. CSD CrossRef CAS Web of Science IUCr Journals Google Scholar
Watkin, D. (1994). Acta Cryst. A50, 411–427. CrossRef CAS Web of Science IUCr Journals Google Scholar
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In an attempt to extend the chemistry of subvalent indium compounds, we have been investigating the feasibility of producing solutions in which an indium(I) halide is acceptably stable to disproportionation at temperatures between 190 and 300 K. One strategy has involved co-condensation of the vapours of the halide and an excess of a potential solvent (e.g. toluene or toluene/ether), followed by warming of the mixture to see whether a solution of practical use in synthesis can be formed. Although ready dissolution without disproportionation is rare, indium(I) iodide has proved to be the halide most prone to dissolve in organic solvents, of which pyridine or pyridine-containing mixtures have been among the most promising. Solutions of indium(I) iodide in a 2:1 pyridine/m-xylene mixture are lastingly stable below 243 K but undergo slow disproportionation at room temperature, giving a mixture of indium metal and triiodotris(pyridine)indium(III). Crystallographic studies of the latter at 150 K have afforded a rare structural characterization of a neutral hexacoordinated indium(III) iodide complex.
The orthorhombic crystals of [InI3(C5H5N)3], (I), consist of neutral molecules with indium in a pseudo-octahedral environment and with the meridional stereochemistry suggested in a preliminary report (Small & Worrall, 1982) but different from that deduced on the basis of IR measurements (Adams et al., 1968). Unlike the corresponding chloride (Jeffs et al., 1984) and bromide (Small & Worrall, 1982) adducts, (I) takes up no additional pyridine molecules of solvation, presumably as a result of the extra bulk of the iodide ligands.
The In—I bond lengths [2.8390 (6) and 2.8676 (3) Å] are comparable to those in the related complex [InI3(4-MeC5H4N)3], (II) [2.803 (4), 2.848 (4) and 2.893 (4) Å; Brown & Tuck, 1996], there being a less pronounced but still distinct shortening of the unique In—I bond trans to the pyridine ring. For these two neutral hexacoordinated InI3 complexes, In—I distances occur therefore in the range 2.80–2.90 Å. As expected, the corresponding distances are shorter in similar pentacoordinated complexes (2.66–2.80 Å), and shorter still in tetracoordinated ones (2.50–2.74 Å), as revealed by the 19 hits in the Cambridge Structural Database (Version 5.26; Allen, 2002). The terminal and bridging In—I distances of the In2I6 molecules of solid indium(III) iodide are 2.644 (2) and 2.842 (2) Å, respectively (Kneep et al., 1982).
The In—N bond lengths in (I), averaging to 2.316 Å, are not significantly different from those in (II) (2.31 Å), [InCl3(C5H5N)3]·C5H5N (2.327 Å) and [InBr3(C5H5N)3]·C5H5N (2.30 Å). In every case, the longest In—N bond is that trans to a halogen, viz. 2.323 (5) versus 2.309 (4) Å in (I), 2.34 (2) versus 2.28 (3)/2.30 (3) Å in (II), 2.377 (21) versus 2.302 (7) Å in [InCl3(C5H5N)3]·C5H5N, and 2.32 (2) versus 2.28 (3)/2.31 (2) Å in [InBr3(C5H5N)3]·C5H5N, even if the difference is not always statistically significant. Any systematic dependence on the nature of the halogen is, at best, small, although no strict comparison can be made in view of the diversity of the data (most of which relate to crystals at room temperature).
The [InI3(C5H5N)3] molecules in (I) each lie on a twofold rotation axis running through the I2—In—N2 bond and parallel to the crystallographic b axis. As in (II), the I1—In—I1i and N1—In—N1i units (symmetry code as in Table 1) depart from linearity, and each pyridine ring is tilted out of the appropriate plane by an average of 40 (2)°, in keeping with the stronger non-bonded repulsion exerted by atom I2 as compared with N2, and minimization of the interaction between the iodide and pyridine functions. By their dimensions, the coordinated pyridine molecules indicate no unusual features. The packing of the molecules of (I) (Fig. 2) gives little evidence of specific interactions. At 3.17 Å, for example, the shortest H···I distance is consistent with a normal van der Waals contact, although the existence of weak hydrogen bonding is not precluded (Table 2). Likewise, short I···I contacts are evidently disfavoured (there are none below 5 Å), which could imply that the I atoms carry a substantial negative charge.