Formation of extended polyiodides at large cation templates

Blake, A.J.; Castellano, C.; Lippolis, V.; Podda, E.; Schröder, M.

doi:10.1107/S2053229624004194

research papers

STRUCTURAL
CHEMISTRY

ISSN: 2053-2296

Volume 80| Part 7| July 2024| Pages 311-318

https://doi.org/10.1107/S2053229624004194

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Formation of extended polyiodides at large cation templates

Alexander J. Blake,^a ^* Carlo Castellano,^b Vito Lippolis,^c Enrico Podda ^d and Martin Schröder ^e

^aSchool of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom, ^bDipartimento di Chimica, Università degli Studi di Milano, Via Golgi 19, Milano, 20133, Italy, ^cDipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Cagliari, S.S. 554 Bivio per Sestu, Monserrato (CA), 09042, Italy, ^dCentre for Research University Services (CeSAR), Università degli Studi di Cagliari, S.S. 554 Bivio per Sestu, Monserrato (CA), 09042, Italy, and ^eDepartment of Chemistry, The University of Manchester, Manchester, M139PL, United Kingdom
^*Correspondence e-mail: alexanderjohnblake@outlook.com

Edited by I. Oswald, University of Strathclyde, United Kingdom (Received 9 April 2024; accepted 7 May 2024; online 13 May 2024)

By studying the structures of (μ-1,4,10,13-tetrathia-7,16-diazacyclooctadecane)bis[iodidopalladium(II)] diiodide penta(diiodine), [Pd₂I₂(C₁₂H₂₆N₂S₄)](I)₂·5I₂ or [Pd₂I₂([18]aneN₂S₄)](I)₂·(I₂)₅, and 4,7,13,16,21,24-hexaoxa-1,10-diazoniabicyclo[8.8.8]hexacosane triiodide iodide hemipenta(diiodine) dichloromethane monosolvate, C₁₈H₃₈N₂O₆²⁺·I₃⁻·I⁻·2.5I₂·CH₂Cl₂ or [H₂([2.2.2]cryptand)](I₃)(I)(I₂)_2.5·CH₂Cl₂, we confirm the structural variety of extended polyiodides achievable upon changing the shape, charge and dimensions of the cation template, by altering the synthetic strategy adopted and/or the experimental conditions. Although it is still often difficult to characterize discrete [I_2m+n]ⁿ⁻ polyiodides higher than I₃⁻ on the basis of structural parameters, such as I—I bond distances, FT–Raman spectroscopy appears to identify them as aggregates of I₂, I⁻ and (symmetric or slightly asymmetric) I₃⁻ building blocks linked by I⋯I interactions of varying strengths. However, because FT–Raman spectroscopy carries no information about the topological features of extended polyiodides, the two techniques should therefore be applied in combination to enhance the analysis of this kind of compounds.

Keywords: crystal structure; mixed-donor macrocycles; [2.2.2]cryptand; palladium(II) complexes; diiodine; polyiodides; FT-Raman spectroscopy.

CCDC references: 2353843; 2353842

1. Introduction

Among extended anionic inorganic frameworks, the formation of polyhalides (Sonnenberg et al., 2020 ; Aragoni et al., 2003 , 2022 ) and, in particular, polyiodides represents a remarkable example of supramolecular self-assembly (Blake et al., 1998c ; Svensson et al., 2003 ), and it continues to capture the interest of many researchers in the field (Savastano, 2021 ; Savastano et al., 2022 ; Horn et al., 2003a ,b ; Aragoni et al., 2004 , 2023a ) due to the richness of its unpredictable and puzzling structural chemistry, and interesting applicative possibilities (Paulsson et al., 2004 ; Yin et al., 2012 ; Fei et al., 2015 ). Iodine and iodides together tend to catenate (Arca et al., 1999 ; Garau et al., 2022 ) via the combination of (Lewis acidic) I₂ with (Lewis basic) I⁻/I₃⁻ building blocks (Ciancaleoni et al., 2016 ). This affords extended arrays exhibiting a range of topologies, and these are highly dependent on the size, shape and charge of the countercation acting as a template. Some polyiodides are present in the crystal structure as discrete aggregates, but frequently they form extended networks in which the identification of the basic repeat unit of general formula [I_n(I₂)_m]ⁿ⁻ or [I_2m+n]ⁿ⁻ (n, m > 0) can become arbitrary. Consequently, they are better described as aggregates of I₂, I⁻ and I₃⁻, held together by I⋯I interactions of varying strengths, from rather strong (ca 3.3 Å) to fairly weak, up to the van der Waals contact distance (ca 4 Å). Our interest in this field has been mainly focused on the use of metal complexes of macrocyclic ligands (mainly thioether crowns) as templating cations for controlling the self-assembly of extended polyiodide arrays (Blake et al., 1996 , 1998a ,b ). These complex cations are relatively chemically inert and their shape, size and charge can be changed readily, thus providing cationic templates for different targeted polyiodide topologies. Furthermore, we have also been interested in the reactivity of macrocyclic ligands with I₂ and inter-halogens IX (X = Br and Cl) to better understand the structural nature of the resulting products (Blake et al., 1997 ). The formation of polyiodide networks featuring spirals, belts, ribbons, sheets and cages as their structural motifs has been achieved either by reacting the PF₆⁻ or BF₄⁻ salts of the complex cation

templates with an excess of I₂ in a single phase, or by addition of an NaI/I₂ mixture in a single phase, the preferred polyiodide being formed via self-assembly. As a further example of the versatility of this synthetic approach to the formation of multidimensional polyiodide networks, we report here the use of the metal complex [Pd₂Cl₂([18]aneN₂S₄)](PF₆)₂ ([18]aneN₂S₄ is 1,4,10,13-tetrathia-7,16-diazacyclooctadecane; see Scheme 1

) and the neutral [2.2.2]cryptand (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane) (Scheme 1

) as templates in the reaction with I₂.

2. Experimental

2.1. Materials and methods

All starting materials, including [18]aneN₂S₄ and [2.2.2]cryptand, and solvents, were obtained from Aldrich or Merck and were used without further purification. [Pd₂Cl₂([18]aneN₂S₄)](PF₆)₂ was prepared according to the literature (Blake et al., 1990 ). Microanalytical data were obtained on a Fisons EA 1108 CHNS-O instrument operating at 1000 °C. FT–Raman spectra (resolution 4 cm⁻¹) were recorded on a Bruker RF100FTR spectrometer fitted with an indium–gallium–arsenide detector operating at room temperature with an excitation wavelength of 1064 nm (Nd:YAG laser). No sample decomposition was observed during the experiments at the power level of the laser source used between 20 and 40 mW. The values in parentheses next to the values represent the intensities of the peaks relative to the strongest, which is taken to be equal to 10.

2.2. Synthesis and crystallization

2.2.1. Synthesis of (I)

To a solution of [Pd₂Cl₂([18]aneN₂S₄)](PF₆)₂ (17.1 mg, 0.019 mmol) in MeCN (4 ml) was added a solution of I₂ (17.7 mg, 0.070 mmol) in MeCN (4 ml). No precipitate formed upon mixing, but dark-brown prismatic crystals of title compound (I) (Scheme 2) formed after several days by slow evaporation of the solvent from the reaction mixture. These were isolated from the mother liquor and washed with diethyl ether (8.4 mg, 36.3% yield). Elemental analysis found [calculated (%) for C₆H₁₃I₇NPdS₂]: C 6.28 (6.22), H 1.15 (1.13), N 1.24 (1.21), S 5.52 (5.54). FT–Raman (range 500–50 cm⁻¹): ν(I–I) 169.7 (10).

2.2.2. Synthesis of (II)

To a solution of [2.2.2]cryptand (20 mg, 0.053 mmol) in CH₂Cl₂ (4 ml) was added a solution of I₂ (53.8 mg, 0.212 mmol) in CH₂Cl₂ (4 ml). A dark-brown microcrystalline precipitate corresponding to the formulation of title compound (II) (Scheme 2) formed immediately. This was isolated by filtration and washed with diethyl ether (58.5 mg, 77.3% yield). Elemental analysis found [calculated (%) for C₁₉H₄₀Cl₂I₉N₂O₆]: C 14.25 (14.21), H 2.47 (2.51), N 1.80 (1.75). FT–Raman (range 500–50 cm⁻¹): ν(I–I) 167.40 (10), 149.8 (6), 106.1 (5). Dark-brown prismatic single crystals suitable for X-ray diffraction analysis were grown from a solution of the obtained solid in MeCN by slow evaporation of the solvent.

2.3. Refinement of X-ray crystal structures

Crystal data, data collection and structure refinement details are summarized in Table 1. H atoms were placed geometrically and refined isotropically riding on their parent C atoms, with U_iso(H) = 1.2U_eq(C). For (II), H atoms bonded to quaternary N atoms could be located from the difference Fourier map and their positions were refined freely. OLEX2 (Dolomanov et al., 2009 ) was used both as the graphical interface for the structural investigation and for the preparation of the figures.

Table 1
Experimental details

For both structures: Z = 4. Experiments were carried out with Mo Kα radiation.

	(I)	(II)
Crystal data
Chemical formula	[Pd₂I₂(C₁₂H₂₆N₂S₄)](I)₂·5I₂	C₁₈H₃₈N₂O₆²⁺·I₃⁻·I⁻·2.5I₂·CH₂Cl₂
M_r	2315.99	1605.53
Crystal system, space group	Monoclinic, C2/c	Monoclinic, P2₁/n
Temperature (K)	220	293
a, b, c (Å)	21.609 (4), 8.198 (3), 24.151 (3)	13.831 (2), 14.820 (2), 20.266 (3)
β (°)	100.170 (13)	96.70 (1)
V (Å³)	4211.1 (18)	4125.6 (10)
μ (mm⁻¹)	11.33	6.92
Crystal size (mm)	0.26 × 0.14 × 0.13	0.2 × 0.15 × 0.11

Data collection
Diffractometer	STOE STADI4 4-circle	Bruker APEXII CCD
Absorption correction	Integration (REDU4; Stoe & Cie, 1996 )	Empirical (using intensity measurements) (SADABS; Bruker, 2001 )
T_min, T_max	0.222, 0.306	0.569, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	4584, 3715, 3059	30347, 8100, 5518
R_int	0.029	0.047
(sin θ/λ)_max (Å⁻¹)	0.595	0.617

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.051, 0.136, 1.08	0.033, 0.088, 1.00
No. of reflections	3715	8100
No. of parameters	163	349
H-atom treatment	H-atom parameters constrained	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	1.35, −1.62	1.37, −1.20
Computer programs: STADI4 (Stoe & Cie, 1996), SAINT (Bruker, 2001), REDU4 (Stoe & Cie, 1996), SHELXS97 (Sheldrick, 1997 ), SHELXT2018 (Sheldrick, 2015a ), SHELXL2018 (Sheldrick, 2015b ) and OLEX2 (Dolomanov et al., 2009).

3. Results and discussion

3.1. Synthesis and crystal structures

Previously, we have reported the crystal structures of [Pd₂Cl₂([18]aneN₂S₄)](I₃)₂ (Blake at al., 1998c,d ) and [Pd₂Cl₂([18]aneN₂S₄)]_1.5(I₅)(I₃)₂ (Blake et al., 1998a,c) obtained from the reaction in MeCN of [Pd₂Cl₂([18]aneN₂S₄)](PF₆)₂ with ⁿBu₄NI and I₂ in 1:2:2 and 1:2:4 molar ratios, respectively. In the former compound, dinuclear palladium(II) complexes are linked via Pd⋯I contacts into ⋯I₃⁻⋯I₃⁻⋯I₃⁻⋯ sinusoidal chains. In [Pd₂Cl₂([18]aneN₂S₄)]_1.5(I₅)(I₃)₂, [Pd₂Cl₂([18]aneN₂S₄)]²⁺ cations are held together by N—H⋯Cl hydrogen bonds and occupy channels formed within the self-assembled three-dimensional (3D) polyiodide network. This network is made up of offset layers of stacked poly-I₃⁻ moieties (including those I₃⁻ belonging to the I₅⁻ units), featuring fused 14- and 24-membered rings interwoven by I₈²⁻ units (I₅⁻⋯I₃⁻). We sought to attempt also the direct reaction of [Pd₂Cl₂([18]aneN₂S₄)](PF₆)₂ with I₂ in the absence of preformed I⁻ (see §2.2.1) and, surprisingly, this afforded a different compound corresponding to the formulation [Pd₂I₂([18]aneN₂S₄)]I₁₂, as deep-red column-shaped crystals. A single-crystal X-ray structure determination (see Table 1 for crystal data) showed an asymmetric unit consisting of half a [Pd₂I₂([18]aneN₂S₄)]²⁺ dication, one iodide anion interacting with two crystallographically-independent I₂ molecules, and an additional half-occupied I₂ molecule disordered across a twofold axis parallel to the b axis. One of the two I atoms is located on a glide plane, thus defining an overall stoichiometry of [Pd₂I₂([18]aneN₂S₄)](I)₂·(I₂)₅, (I), for the obtained salt. The complete dication is generated through an inversion centre and features the hexadentate macrocycle binding to the two metal centres via NS₂ coordination. A distorted square-planar coordination geometry at each Pd^II metal ion is completed by coordinated iodide anions that have replaced the chloride ions (Fig. 1) in the starting material upon reaction with I₂ (see Table 2 for selected geometric parameters).

Table 2
Selected geometric parameters (Å, °)

[Pd₂I₂([18]aneN₂S₄)](I)₂·(I₂)₅, (I)
Pd—I	2.5722 (14)	S7—C8	1.816 (12)
Pd—N1	2.076 (9)	C8—C9	1.511 (16)
Pd—S4	2.314 (3)	I—Iⁱⁱ	3.545 (2)
Pd—S7ⁱ	2.313 (3)	I1—I2	2.7899 (15)
N1—C2	1.459 (15)	I2—I3	3.1214 (16)
N1—C9ⁱ	1.489 (16)	I3—I4	3.205 (2)
C2—C3	1.514 (17)	I4—I5	2.7644 (16)
C3—S4	1.809 (11)	I3—I6	3.351 (3)
S4—C5	1.838 (10)	I6—I7	2.771 (4)
C5—C6	1.507 (15)	I7—I3ⁱⁱⁱ	3.432 (3)
C6—S7	1.796 (10)

N1—Pd—S4	86.8 (3)	S7ⁱ—Pd—I	92.20 (8)
N1—Pd—S7ⁱ	87.7 (3)	S7ⁱ—Pd—S4	173.88 (11)
S4—Pd—I	93.57 (8)

[H₂([2.2.2]cryptand)](I₃)(I)(I₂)_2.5·CH₂Cl₂, (II)
I3—I2	2.9799 (8)	O1—C2	1.402 (8)
I3—I4	2.8629 (8)	O1—C3	1.422 (8)
I6—I5	2.8015 (8)	O2—C4	1.426 (8)
I6—I7	3.0952 (8)	O2—C5	1.430 (8)
I8—I9	2.8001 (8)	O3—C9	1.415 (8)
I8—I7	3.0940 (9)	O3—C8	1.431 (8)
I1—I1^iv	2.7595 (11)	O4—C11	1.421 (8)
N1—C1	1.495 (9)	O4—C10	1.428 (8)
N1—C12	1.493 (8)	O5—C17	1.421 (8)
N1—C13	1.507 (8)	O5—C16	1.403 (8)
N2—C6	1.500 (8)	O6—C15	1.408 (8)
N2—C7	1.495 (8)	O6—C14	1.429 (8)
N2—C18	1.506 (8)

I4—I3—I2	176.54 (2)	I9—I8—I7	175.52 (2)
I5—I6—I7	173.63 (2)	I8—I7—I6	89.70 (2)
Symmetry codes: (i) −x + $[{3\over 2}]$ , −y + $[{1\over 2}]$ , −z + 1; (ii) −x + $[{3\over 2}]$ , −y − $[{1\over 2}]$ , −z + 1; (iii) −x + 1, y + 1, −z + $[{1\over 2}]$ ; (iv) −x + 2, −y + 1, −z.

Figure 1
View of the dication in (I)

, showing the atom-numbering scheme adopted. Displacement ellipsoids are drawn at the 50% probability level. Intramolecular C—H⋯I hydrogen bonds: C6⋯I = 3.779 (11), H6A⋯I = 2.84, C5ⁱ⋯I = 3.755 (10), H5A⋯I = 2.80 Å, C6—H6A⋯I = 162 and C5—H5A⋯Iⁱ = 161°. [Symmetry code: (i) −x + $[{3\over 2}]$ , −y + $[{1\over 2}]$ , −z + 1.]

In (I), the Pd—N [Pd—N1 = 2.076 (9) Å] and Pd—S [Pd—S4 = 2.314 (3) and Pd—S7ⁱ = 2.313 (3) Å; symmetry code: (i) −x + $[{3\over 2}]$ , −y + $[{1\over 2}]$ , −z + 1] distances are very close to those observed in previously reported [Pd₂Cl₂([18]aneN₂S₄)]²⁺ dications (Blake et al., 1990, 1998a,c,d), while the Pd—I bond distance [2.5722 (14) Å] is significantly longer than the Pd—Cl distances [2.305 (4)–2.374 (1) Å]. As with the [Pd₂Cl₂([18]aneN₂S₄)]²⁺ dications reported previously, the dications in (I) adopt a stepped conformation. Interestingly, in [Pd₂Cl₂([18]aneN₂S₄)]_1.5(I₅)(I₃)₂ (Blake et al., 1998a,c), the dications are linked pairwise by hydrogen bonds between the (N)H and Cl atoms to form extended chains. The [Pd₂I₂([18]aneN₂S₄)]²⁺ dications in (I) are linked by intermolecular I⋯I contacts of 3.545 (2) Å to form chains running parallel to the b axis (Fig. 2). In both compounds, the complex dications feature intermolecular interactions of the type C—H⋯X (X = Cl and I) (see Figs. 1 and 2).

Figure 2
View of a chain of interacting [Pd₂I₂([18]aneN₂S₄)]²⁺ dications found in the crystal structure of (I)

. The dications are arranged into chains via I⋯I interactions of 3.545 (2) Å running along the b axis. [Symmetry codes: (i) −x + $[{3\over 2}]$ , −y + $[{1\over 2}]$ , −z + 1; (ii) −x + $[{3\over 2}]$ , −y − $[{1\over 2}]$ , −z + 1.]

The polyiodide network in (I) can also be regarded as comprising I₁₂²⁻ anions (Fig. 3) built up by [(I⁻)₂·(I₂)₅] adducts formed by interaction of the disordered I₂ molecules (I6—I7) [2.771 (4) Å] and `V-shaped' I₅⁻ of the type [(I⁻)·(I₂)₂] with the iodide anion (I3) interacting with two crystallographically-independent I₂ molecules [I1—I2 and I4—I5: I1—I2 = 2.7899 (15), I2⋯I3 = 3.1214 (16), I4—I5 = 2.7644 (16), I3⋯I4 = 3.205 (2) Å, I1—I2⋯I3 = 173.23 (5), I3⋯I4—I5 = 173.60 (5) and I2⋯I3⋯I4 = 95.36 (4)°].

Figure 3
View of the two symmetry-related I₁₂²⁻ anions in (I)

formed by the interaction of the two components of the disordered I₂ molecules with two `V-shaped' I₅⁻ moieties of the type [(I⁻)·(I₂)₂]. [Symmetry codes: (iii) x, y + 1, z; (iv) −x + 1, y + 1, −z + $[{1\over 2}]$ ; (v) −x + 1, y, −z + $[{1\over 2}]$ .]

Each component of the disordered and half-occupied I₂ molecule interacts at both I atoms with the iodide atom (I3) of the I₅⁻ moiety via I⋯I interactions of 3.351 (3) (I3⋯I6) and 3.432 (3) Å [I7⋯I3^iv; symmetry code: (iv) −x + 1, y + 1, −z + $[{1\over 2}]$ ]. This gives rise to two I₁₂²⁻ anions in the structure, which are symmetry-related by a screw axis parallel to the b axis and a glide plane (the same symmetry elements that relate the two disorder components of the half-occupied I6—I7 diiodine molecule) (Fig. 3).

I₁₂²⁻ of the same orientation (blue or green in Fig. 3) interact with each other via I⋯I interactions of 3.625 (2) [I1⋯I7^vi; symmetry code: (vi) x − $[{1\over 2}]$ , y − $[{1\over 2}]$ , z] and 3.800 (2) Å [I6⋯I5^vii; symmetry code: (vii) −x + 1, −y + 1, −z + 1] (Fig. 4) to give one-dimensional (1D) tubes of fused pseudo-cubic cavities defined by 8- and 14-membered polyiodide rings (Fig. 4). Two differently-oriented 1D tubes of this type therefore co-exist at 50% occupancy in the crystal structure, depending on the orientation of the generating I₁₂²⁻ units; one type is approximately perpendicular and the other approximately parallel to the [110] direction (blue and green, respectively, in Fig. 5).

Figure 4
View along the b axis of one of the two 1D polyiodide tubes in (I)

formed via I₁₂²⁻⋯I₁₂²⁻ interactions involving I₁₂²⁻ anions of the same orientation (in this case, I₁₂²⁻ is the component depicted in green as in Fig. 3

). [Symmetry codes: (iv) −x + 1, y + 1, −z + $[{1\over 2}]$ ; (vi) x − $[{1\over 2}]$ , y − $[{1\over 2}]$ , z; (vii) −x + 1, −y + 1, −z + 1.]

Figure 5
View of the two differently-oriented polyiodide 1D tubes of interacting I₁₂²⁻ units co-existing at 50% occupancy in the crystal structure of (I)

. Colours are consistent with those in Fig. 3

for the differently-oriented I₁₂²⁻ units generating the two 1D polyiodides tubes.

Chains of [Pd₂I₂([18]aneN₂S₄)]²⁺ complex dications (Fig. 2) run parallel to the b axis crossing adjacent 1D polyiodide tubes through the pseudo-cubic cavities (Fig. 6). It is interesting to note that, as the I7 atom of the disordered I₂ molecule lies on a glide plane, the resulting ratio between the two components is imposed by symmetry and the maximum occupancy possible is 0.5. As a consequence, the ratio between the two types of tubes described above remains constant in the crystal structure and cannot vary between different crystals. That said, a unique crystal packing is observed in the crystal structure of (I) featuring the two sets of tubes formed by fused pseudo-cubic boxes (see above) running parallel (green) and perpendicular (blue) to the [110] direction, alternatively layered along the c axis [Figs. 6(b) and 6(c)].

Figure 6
(a) View along the b axis of the crystal packing in (I)

, showing the relative positions between the 1D polyiodide tubes and the chains of [Pd₂I₂([18]aneN₂S₄)]²⁺ complex dications. The polyiodide network is also portrayed in parts (b) and (c) as blue and green tubes according to Fig. 3

, and cations are coloured according to the type of tubes they cross.

To illustrate further the importance of the shape, charge and dimensions of the template cation in the polyiodide network assembly, we treated the macropolycyclic ligand [2.2.2]cryptand (Scheme 1) with I₂ in a 1:4 molar ratio in CH₂Cl₂. Upon slow evaporation of the solvent at room temperature, dark prismatic crystals formed corresponding to the formulation [H₂([2.2.2]cryptand)]I₉·CH₂Cl₂, (II). An X-ray crystal structure determination (see Table 1 for crystal data) confirmed the presence of an asymmetric unit consisting of an [H₂([2.2.2]cryptand)]²⁺ dication in which both tertiary N atoms of the starting macropolycyclic ligand are protonated (Fig. 7). Half an I₂ molecule [I1—I1ⁱ = 2.7595 (11) Å; symmetry code: (i) −x + 2, −y + 1, −z], an asymmetric triiodide [I2—I3—I4: I2—I3 = 2.9799 (8) and I3—I4 = 2.8629 (8) Å], a `V-shaped' pentaiodide consisting of an iodide anion (I7) interacting with two diiodine molecules [(I⁻)·(I₂)₂] (I5—I6 and I8—I9) [I5—I6 = 2.8015 (8), I8—I9 = 2.8001 (8), I6—I7 = 3.0952 (8) and I7—I8 = 3.0940 (9) Å] and a cocrystallized CH₂Cl₂ solvent molecule define the [H₂([2.2.2]cryptand)](I₃)(I)(I₂)_2.5·CH₂Cl₂ (II) stoichiometry for the obtained polyiodide salt (see Table 2 for selected geometric parameters).

Figure 7
The crystal structure of (II)

, showing the numbering scheme adopted. Displacement ellipsoids are drawn at the 50% probability level. H atoms and the cocrystallized CH₂Cl₂ molecules are not shown. [Symmetry code: (i) −x + 2, −y + 1, −z.]

In (II), all three diiodine molecules are slightly elongated with respect to the I—I distance found in the crystal structure of orthorhombic I₂ [2.715 (6) Å] (Blake et al., 1998b). Each I1 atom interacts with an asymmetric triiodide unit at the I2 atom to afford a `Z-shaped' I₈²⁻ dianion [I1⋯I2 = = 3.4123 (9) Å] that can be regarded as an I₃⁻·I₂·I₃⁻ [(I₃⁻)₂·(I₂)] complex (Savastano et al., 2022). Additional longer contacts of 3.907 (1) Å, still within the sum of the van der Waals radii for iodine, between each I1 atom and the terminal iodine (I5) of a pentaiodide moiety, lead to an overall discrete `grasshopper-shaped' I₁₈⁴⁻ polyiodide. This can be envisaged as an [(I₈²⁻)·(I₅⁻)₂] with a long contact between the I₈²⁻ anion and the two I₅⁻ moieties or, in terms of fundamental building blocks, as an [(I⁻)₂·(I₃⁻)₂·(I₂)₅] adduct (Fig. 8). I₁₈⁴⁻ polyiodides are quite rare in the literature: in [Co(12C4)₂]₂(I₁₈) (12C4 is 12-crown-4), a unique central planar I₉⁻ [(I⁻)·(I₂)₄] is attached to four triiodides at I⋯I distances of 3.240 (4)–3.478 (4) Å, and the [(I₉⁻)(I₃⁻)₄] units are connected via two bridging I₃⁻ to form polymeric chains of I₁₈⁴⁻ = [(I₉⁻)(I₃⁻)_2/1(I₃⁻)_2/2] (Fiolka et al. 2011 ); in [SnI₂(mbit)₂](I₃)₂· $[2 \over 3]$ I₂ [mbit is 1,1′-bis(3-methyl-4-imidazoline-2-thione)methane], two I₈²⁻ dianions of the type I₂·I⁻·I₂·I⁻·I₂ [(I⁻)₂·(I₂)₃] and related through an inversion centre are linked to each other at the iodide atoms by a bridging disordered I₂ molecule via non-negligible I⋯I interactions of 3.55 (1) Å (Bigoli et al., 1998 ).

Figure 8
(a)/(b) Views of the I₁₈⁴⁻ polyiodide in (II)

formed by interaction of a central diiodine molecule with two I₃⁻ and two I₅⁻ [(I⁻)·(I₂)₂] species, showing the numbering scheme adopted. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry code: (i) −x + 2, −y + 1, −z.]

The discrete I₁₈⁴⁻ polyiodide units are located side-by-side and interdigitated along the [101] direction, with [H₂([2.2.2]cryptand)]²⁺ dications sitting in the resulting voids (Fig. 9).

Figure 9
Views along approximately (a) the a axis and (b) the [101] direction of the crystal packing in (II)

. The blue colour and the ball-and-stick representation have been used for one of the discrete I₁₈⁴⁻ polyiodide units to better highlight its atomic connectivity in the crystal packing. H atoms and the cocrystallized CH₂Cl₂ molecules are not shown.

3.2. FT–Raman spectroscopy

Despite the high number of extended polyiodides that have been structurally characterized, and the associated crystal structure data available, the assignment of higher molecular polyiodides (higher than I₃⁻) with their own distinctive structural features is still a matter of debate (Savastano et al., 2022). The reductionist approach whereby higher polyiodides are considered as aggregates of I₂, I⁻ and I₃⁻ held together by I⋯I interactions of varying strengths, from rather strong (up to ca 3.3–3.4 Å) (covalent interactions) to fairly weak (up to the van der Waals contact distance, ca 4 Å) (supramolecular interactions), is still the most reasonable and least arbitrary. On the basis of structural data, all known higher discrete polyiodides can be regarded, therefore, as weak or medium-weak adducts of the type [(I⁻)_n–y·(I₃⁻)_y·(I₂)_m–y] ≡ [I_2m+n]ⁿ⁻ (n, m > 0), whose geometrical and topological features can be very different and often unpredictable (Arca et al. 2006 ). This way of considering higher polyiodides from a structural point of view is strongly supported by spectroscopic evidence. In particular, FT–Raman spectroscopy confirms that extended polyiodides do not have distinctive vibrational properties other than those of perturbed (slightly elongated) I₂ molecules and symmetric/slightly asymmetric I₃⁻. Perturbed I₂ molecules are characterized by only one strong band in the range 180–140 cm⁻¹ in the FT–Raman spectrum, the wavenumber depending on the extent of the I⋯I elongation; for linear and symmetric I₃⁻, only the Raman-active symmetric stretch (ν₁) occurs near 110 cm⁻¹, while the antisymmetric stretch (ν₃) and the bending deformation (ν₂) are only IR-active (Aragoni et al., 2023b ). The latter two modes also become Raman-active for slightly asymmetric I₃⁻ and they are found near 134 (ν₃) and 80 cm⁻¹ (ν₂), having medium and medium–weak intensities, respectively. Highly asymmetric I₃⁻ ions show only one band in their FT–Raman spectra in the range 180–140 cm⁻¹, so that they should be regarded as weak (I⁻)·I₂ adducts. To date, FT–Raman spectra of polyiodides of the general formula [I_2m+n]ⁿ⁻ show peaks in the low wavenumber region with either one strong peak in the range 180–140 cm⁻¹ or the characteristic peaks due to both perturbed I₂ and symmetric/slightly asymmetric I₃⁻. They would therefore be better described as [(I⁻)_n·(I₂)_m] or [(I⁻)_n–y·(I₃⁻)_y·(I₂)_m–y] (n > y ≠ 0)/[(I₃⁻)_n·(I₂)_m–n] (n = y ≠ 0) systems. The polyiodides here described are no exception. The FT–Raman spectrum of (I) features only a strong and broad peak centred at 169 cm⁻¹ indicative of the presence of differently perturbed I₂ molecules (Fig. S1 in the supporting information). The FT–Raman spectrum of (II) is shown in Fig. 10. The two peaks at about 167 and 150 cm⁻¹ can be assigned to the stretching vibration of the two differently elongated I₂ molecules I5—I6/I6—I7 and I1—I1ⁱ [symmetry code: (i) −x + 2, −y + 1, −z], respectively. These data correspond closely to the established linear correlation ν(I–I)/cm⁻¹ versus d(I–I)/Å for weak or medium–weak adducts (Arca et al., 2006). The peak at 106 cm⁻¹ can be attributed to the symmetric stretch (ν₁) of the I₃⁻ ion (I2—I3—I4), thus confirming the description of the I₁₈⁴⁻ polyiodide as an [(I⁻)₂·(I₃⁻)₂·(I₂)₅] adduct.

Figure 10
FT–Raman spectrum of (II)

in the low frequency region.

4. Conclusions

In this article, we confirm the structural variety of extended polyiodides that can be generated by changing the shape, charge and dimension of the cation template, as well as the synthetic strategy adopted and the experimental conditions. Although it is still often difficult to characterize [I_2m+n]ⁿ⁻ polyiodides higher than I₃⁻ on the grounds of any distinctive structural parameters, such as I—I bond distances, FT–Raman spectroscopy appears to confirm their characterization as aggregates of I₂, I⁻ and (symmetric or slightly asymmetric) I₃⁻ building blocks held together by I⋯I interactions of varying strengths. On the other hand, FT–Raman spectroscopy cannot provide any information on the topological features of extended polyiodides. The two techniques should therefore be used together in the analysis of this kind of compound.

Supporting information

CCDC references: 2353843; 2353842

Crystal structure: contains datablocks I, II, global. DOI: https://doi.org/10.1107/S2053229624004194/vp3036sup1.cif

Structure factors: contains datablock i. DOI: https://doi.org/10.1107/S2053229624004194/vp3036isup2.hkl

Structure factors: contains datablock ii. DOI: https://doi.org/10.1107/S2053229624004194/vp3036iisup3.hkl

Additional FT-Raman spectrum. DOI: https://doi.org/10.1107/S2053229624004194/vp3036sup4.pdf

Computing details top

(µ-1,4,10,13-Tetrathia-7,16-diazacyclooctadecane)bis[iodidopalladium(II)] diiodide penta(diiodine) (I) top

Crystal data top

[Pd₂I₂(C₁₂H₂₆N₂S₄)](I)₂·5I₂	F(000) = 4040
M_r = 2315.99	D_x = 3.653 Mg m⁻³
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 21.609 (4) Å	Cell parameters from 25 reflections
b = 8.198 (3) Å	θ = 5–20°
c = 24.151 (3) Å	µ = 11.33 mm⁻¹
β = 100.170 (13)°	T = 220 K
V = 4211.1 (18) Å³	Column, red
Z = 4	0.26 × 0.14 × 0.13 mm

Data collection top

STOE STADI4 4-circle diffractometer	R_int = 0.029
Scan width (ω) = 1.64 – 2.20, scan ratio 2θ:ω = 1.00 I(Net) and sigma(I) from profile fitting (Clegg, 1981)	θ_max = 25.0°, θ_min = 2.7°
Absorption correction: integration (REDU4; Stoe & Cie, 1996)	h = −25→25
T_min = 0.222, T_max = 0.306	k = 0→9
4584 measured reflections	l = −28→28
3715 independent reflections	3 standard reflections every 60 reflections
3059 reflections with I > 2σ(I)	intensity decay: 5.0%

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.051	H-atom parameters constrained
wR(F²) = 0.136	w = 1/[σ²(F_o²) + (0.0681P)² + 91.8532P] where P = (F_o² + 2F_c²)/3
S = 1.08	(Δ/σ)_max = 0.001
3715 reflections	Δρ_max = 1.35 e Å⁻³
163 parameters	Δρ_min = −1.61 e Å⁻³
0 restraints

Special details top

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

Refinement. Diffraction data were collected on Stoe STADI4 4-circle and APEXII CCD area detector diffractometers for [Pd₂I₂([18]aneN₂S₄)](I)₂.(I₂)₅, (I)< and [H₂([2.2.2]cryptand)](I₃)(I)(I₂)_2.5.CH₂Cl₂, (II), respectively. The structures were solved by direct methods using SHELXS (Sheldrick, 1997) or SHELXT2018 (Sheldrick, 2015a) and developed by iterative cycles of least-squares refinement on F² using SHELXL2018 (Sheldrick, 2015b). OLEX2 (Dolomanov et al., 2009) was used both as the graphical interface for the structural investigation and for the preparation of the figures.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Pd	0.74558 (4)	0.20976 (10)	0.41095 (3)	0.0265 (2)
I	0.74355 (4)	−0.07058 (10)	0.45843 (3)	0.0396 (2)
N1	0.7472 (4)	0.4224 (12)	0.3645 (4)	0.033 (2)
H1	0.745717	0.388974	0.324940	0.039*
C2	0.6914 (6)	0.5217 (15)	0.3658 (5)	0.036 (3)
H2A	0.689655	0.611209	0.338668	0.043*
H2B	0.693364	0.568860	0.403345	0.043*
C3	0.6334 (5)	0.4162 (15)	0.3512 (4)	0.032 (3)
H3A	0.628665	0.382092	0.311775	0.039*
H3B	0.596243	0.480422	0.355395	0.039*
S4	0.63730 (13)	0.2371 (4)	0.39546 (11)	0.0307 (6)
C5	0.6221 (5)	0.3303 (14)	0.4610 (4)	0.028 (2)
H5A	0.654611	0.411792	0.474030	0.034*
H5B	0.581340	0.385964	0.453828	0.034*
C6	0.6220 (5)	0.2026 (14)	0.5058 (4)	0.029 (2)
H6A	0.650767	0.114176	0.500145	0.035*
H6B	0.579687	0.156393	0.502622	0.035*
S7	0.64573 (13)	0.2877 (4)	0.57479 (11)	0.0283 (6)
C8	0.6386 (5)	0.1087 (15)	0.6175 (5)	0.033 (3)
H8A	0.637648	0.143110	0.656212	0.040*
H8B	0.598808	0.053577	0.603074	0.040*
C9	0.6921 (6)	−0.0100 (14)	0.6177 (5)	0.033 (3)
H9A	0.688681	−0.099724	0.643794	0.040*
H9B	0.690389	−0.055880	0.580004	0.040*
I1	0.17411 (5)	0.49110 (13)	0.27632 (4)	0.0541 (3)
I2	0.30416 (5)	0.44729 (11)	0.29934 (3)	0.0471 (3)
I3	0.44647 (5)	0.35848 (16)	0.33110 (4)	0.0632 (3)
I4	0.44322 (4)	0.28503 (11)	0.46091 (4)	0.0498 (3)
I5	0.45421 (5)	0.21053 (14)	0.57386 (5)	0.0615 (3)
I6	0.48062 (11)	0.7092 (3)	0.27188 (9)	0.0694 (6)	0.5
I7	0.50658 (10)	1.0005 (3)	0.22248 (9)	0.0692 (6)	0.5

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Pd	0.0277 (4)	0.0317 (5)	0.0191 (4)	0.0014 (4)	0.0018 (3)	0.0031 (3)
I	0.0446 (5)	0.0385 (5)	0.0356 (4)	0.0007 (4)	0.0066 (3)	0.0056 (3)
N1	0.036 (5)	0.036 (5)	0.025 (5)	0.005 (4)	0.004 (4)	0.007 (4)
C2	0.040 (6)	0.034 (6)	0.032 (6)	0.005 (5)	0.002 (5)	0.011 (5)
C3	0.033 (6)	0.041 (7)	0.021 (5)	0.010 (5)	−0.003 (4)	0.007 (5)
S4	0.0275 (13)	0.0446 (17)	0.0183 (12)	0.0019 (12)	−0.0011 (10)	0.0005 (12)
C5	0.031 (5)	0.034 (6)	0.019 (5)	0.006 (5)	0.005 (4)	0.000 (5)
C6	0.032 (6)	0.038 (6)	0.015 (5)	0.000 (5)	−0.004 (4)	−0.004 (5)
S7	0.0296 (13)	0.0367 (15)	0.0189 (12)	0.0031 (12)	0.0048 (10)	0.0007 (11)
C8	0.030 (6)	0.042 (7)	0.027 (6)	0.000 (5)	0.005 (5)	−0.005 (5)
C9	0.048 (7)	0.027 (6)	0.026 (6)	−0.004 (5)	0.011 (5)	0.000 (5)
I1	0.0707 (6)	0.0609 (6)	0.0275 (4)	0.0073 (5)	−0.0003 (4)	−0.0030 (4)
I2	0.0735 (6)	0.0451 (5)	0.0243 (4)	−0.0062 (4)	0.0128 (4)	−0.0044 (3)
I3	0.0516 (6)	0.0845 (8)	0.0538 (6)	−0.0055 (5)	0.0096 (5)	−0.0075 (5)
I4	0.0310 (4)	0.0478 (5)	0.0666 (6)	0.0020 (4)	−0.0023 (4)	−0.0141 (5)
I5	0.0483 (5)	0.0740 (7)	0.0617 (6)	0.0060 (5)	0.0080 (5)	−0.0112 (5)
I6	0.0612 (12)	0.0961 (17)	0.0465 (11)	0.0254 (12)	−0.0021 (9)	−0.0094 (11)
I7	0.0578 (12)	0.1024 (18)	0.0451 (10)	0.0283 (12)	0.0026 (9)	−0.0041 (11)

Geometric parameters (Å, º) top

Pd—I	2.5722 (14)	C5—H5B	0.9800
Pd—N1	2.076 (9)	C5—C6	1.507 (15)
Pd—S4	2.314 (3)	C6—H6A	0.9800
Pd—S7ⁱ	2.313 (3)	C6—H6B	0.9800
N1—H1	0.9900	C6—S7	1.796 (10)
N1—C2	1.459 (15)	S7—C8	1.816 (12)
N1—C9ⁱ	1.489 (16)	C8—H8A	0.9800
C2—H2A	0.9800	C8—H8B	0.9800
C2—H2B	0.9800	C8—C9	1.511 (16)
C2—C3	1.514 (17)	C9—H9A	0.9800
C3—H3A	0.9800	C9—H9B	0.9800
C3—H3B	0.9800	I1—I2	2.7899 (15)
C3—S4	1.809 (11)	I3—I7ⁱⁱ	3.432 (3)
S4—C5	1.838 (10)	I4—I5	2.7644 (16)
C5—H5A	0.9800	I6—I7	2.771 (4)

N1—Pd—I	173.8 (3)	S4—C5—H5A	109.5
N1—Pd—S4	86.8 (3)	S4—C5—H5B	109.5
N1—Pd—S7ⁱ	87.7 (3)	H5A—C5—H5B	108.1
S4—Pd—I	93.57 (8)	C6—C5—S4	110.7 (8)
S7ⁱ—Pd—I	92.20 (8)	C6—C5—H5A	109.5
S7ⁱ—Pd—S4	173.88 (11)	C6—C5—H5B	109.5
Pd—N1—H1	106.8	C5—C6—H6A	109.4
C2—N1—Pd	111.4 (7)	C5—C6—H6B	109.4
C2—N1—H1	106.8	C5—C6—S7	111.1 (8)
C2—N1—C9ⁱ	114.4 (9)	H6A—C6—H6B	108.0
C9ⁱ—N1—Pd	110.3 (7)	S7—C6—H6A	109.4
C9ⁱ—N1—H1	106.8	S7—C6—H6B	109.4
N1—C2—H2A	109.8	C6—S7—Pdⁱ	104.9 (4)
N1—C2—H2B	109.8	C6—S7—C8	100.0 (5)
N1—C2—C3	109.3 (10)	C8—S7—Pdⁱ	96.2 (4)
H2A—C2—H2B	108.3	S7—C8—H8A	109.1
C3—C2—H2A	109.8	S7—C8—H8B	109.1
C3—C2—H2B	109.8	H8A—C8—H8B	107.9
C2—C3—H3A	109.2	C9—C8—S7	112.4 (8)
C2—C3—H3B	109.2	C9—C8—H8A	109.1
C2—C3—S4	112.1 (7)	C9—C8—H8B	109.1
H3A—C3—H3B	107.9	N1ⁱ—C9—C8	109.0 (9)
S4—C3—H3A	109.2	N1ⁱ—C9—H9A	109.9
S4—C3—H3B	109.2	N1ⁱ—C9—H9B	109.9
C3—S4—Pd	96.6 (4)	C8—C9—H9A	109.9
C3—S4—C5	100.0 (5)	C8—C9—H9B	109.9
C5—S4—Pd	103.3 (4)	H9A—C9—H9B	108.3

Pd—N1—C2—C3	−49.8 (11)	S4—C5—C6—S7	151.6 (6)
Pd—S4—C5—C6	−81.5 (8)	C5—C6—S7—Pdⁱ	−82.2 (8)
Pdⁱ—S7—C8—C9	−30.4 (8)	C5—C6—S7—C8	178.6 (8)
N1—C2—C3—S4	53.8 (11)	C6—S7—C8—C9	76.0 (9)
C2—C3—S4—Pd	−29.9 (9)	S7—C8—C9—N1ⁱ	54.5 (11)
C2—C3—S4—C5	74.9 (9)	C9ⁱ—N1—C2—C3	−175.8 (9)
C3—S4—C5—C6	179.2 (8)

Symmetry codes: (i) −x+3/2, −y+1/2, −z+1; (ii) −x+1, y−1, −z+1/2.

4,7,13,16,21,24-Hexaoxa-1,10-diazoniabicyclo[8.8.8]hexacosane triiodide iodide hemipenta(diiodine) dichloromethane monosolvate (II) top

Crystal data top

C₁₈H₃₈N₂O₆²⁺·I₃⁻·I⁻·2.5I₂·CH₂Cl₂	F(000) = 2908
M_r = 1605.53	D_x = 2.585 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.71073 Å
a = 13.831 (2) Å	Cell parameters from 1024 reflections
b = 14.820 (2) Å	θ = 2.3–25.0°
c = 20.266 (3) Å	µ = 6.92 mm⁻¹
β = 96.70 (1)°	T = 293 K
V = 4125.6 (10) Å³	Prism, dark brown
Z = 4	0.2 × 0.15 × 0.11 mm

Data collection top

Bruker APEXII CCD diffractometer	5518 reflections with I > 2σ(I)
ω scan	R_int = 0.047
Absorption correction: empirical (using intensity measurements) (SADABS; Bruker, 2001)	θ_max = 26.0°, θ_min = 1.7°
T_min = 0.569, T_max = 1.000	h = −17→17
30347 measured reflections	k = −17→18
8100 independent reflections	l = −24→24

Refinement top

Refinement on F²	Primary atom site location: dual
Least-squares matrix: full	Hydrogen site location: mixed
R[F² > 2σ(F²)] = 0.033	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.088	w = 1/[σ²(F_o²) + (0.0409P)² + 2.6443P] where P = (F_o² + 2F_c²)/3
S = 1.00	(Δ/σ)_max = 0.002
8100 reflections	Δρ_max = 1.37 e Å⁻³
349 parameters	Δρ_min = −1.20 e Å⁻³
0 restraints

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
I3	0.97532 (3)	0.09815 (3)	−0.09154 (2)	0.05246 (13)
I6	1.18118 (3)	0.25227 (3)	0.29099 (2)	0.05446 (13)
I8	1.02564 (4)	0.12201 (3)	0.44048 (2)	0.05614 (13)
I1	1.04190 (4)	0.41593 (4)	−0.00367 (2)	0.06090 (14)
I5	1.14617 (4)	0.36573 (4)	0.18021 (3)	0.06725 (15)
I9	0.84017 (4)	0.12912 (4)	0.48279 (3)	0.07124 (16)
I2	1.11920 (4)	0.19711 (4)	0.00283 (3)	0.07161 (16)
I4	0.84421 (4)	−0.00647 (4)	−0.18076 (3)	0.07345 (17)
I7	1.23723 (4)	0.11657 (4)	0.40516 (3)	0.08026 (18)
Cl1	0.95495 (16)	0.38674 (16)	0.32137 (13)	0.0828 (6)
Cl2	0.7726 (2)	0.39206 (15)	0.37582 (16)	0.1031 (9)
O3	1.0138 (3)	0.5948 (3)	0.4173 (2)	0.0507 (11)
O4	0.8153 (3)	0.6262 (3)	0.4468 (2)	0.0505 (11)
O6	0.7318 (3)	0.8559 (3)	0.3468 (2)	0.0572 (12)
O5	0.9379 (3)	0.8313 (3)	0.3301 (2)	0.0546 (12)
O2	0.8968 (3)	0.6260 (3)	0.2316 (2)	0.0557 (12)
O1	0.7020 (3)	0.6014 (3)	0.2611 (2)	0.0571 (12)
N2	1.0574 (4)	0.6895 (4)	0.3026 (3)	0.0418 (12)
H2	1.001 (5)	0.686 (4)	0.314 (3)	0.050*
N1	0.6452 (4)	0.6877 (3)	0.3760 (3)	0.0413 (12)
H1	0.699 (5)	0.691 (4)	0.362 (3)	0.050*
C11	0.7283 (5)	0.6077 (5)	0.4753 (4)	0.0549 (18)
H11A	0.716852	0.654111	0.507249	0.066*
H11B	0.733234	0.549923	0.497966	0.066*
C7	1.1296 (4)	0.6832 (4)	0.3634 (3)	0.0473 (16)
H7A	1.125640	0.737570	0.389610	0.057*
H7B	1.194607	0.680113	0.350046	0.057*
C9	0.9878 (5)	0.6552 (5)	0.4663 (4)	0.0548 (18)
H9A	0.975004	0.714386	0.446738	0.066*
H9B	1.041407	0.660797	0.501438	0.066*
C2	0.6032 (5)	0.6010 (5)	0.2706 (4)	0.0609 (19)
H2A	0.587977	0.544205	0.290791	0.073*
H2B	0.564287	0.604898	0.227653	0.073*
C15	0.8113 (5)	0.8730 (5)	0.3951 (4)	0.0540 (17)
H15A	0.827712	0.818663	0.420665	0.065*
H15B	0.793995	0.919471	0.425342	0.065*
C8	1.1135 (5)	0.6028 (5)	0.4057 (4)	0.0542 (18)
H8A	1.132992	0.548567	0.383870	0.065*
H8B	1.154018	0.608160	0.447929	0.065*
C12	0.6466 (5)	0.6061 (4)	0.4194 (4)	0.0549 (18)
H12A	0.653090	0.552702	0.392511	0.066*
H12B	0.585150	0.601838	0.437805	0.066*
C4	0.8137 (5)	0.6384 (6)	0.1838 (3)	0.062 (2)
H4A	0.797239	0.581965	0.161018	0.074*
H4B	0.828128	0.682662	0.151120	0.074*
C6	1.0670 (5)	0.6125 (5)	0.2557 (4)	0.0565 (18)
H6A	1.069183	0.556145	0.280203	0.068*
H6B	1.127538	0.618509	0.236363	0.068*
C17	1.0294 (5)	0.8552 (5)	0.3096 (4)	0.061 (2)
H17A	1.077173	0.864245	0.348067	0.073*
H17B	1.023659	0.910587	0.284027	0.073*
C13	0.6242 (5)	0.7734 (4)	0.4118 (4)	0.0523 (17)
H13A	0.557033	0.772228	0.421256	0.063*
H13B	0.665384	0.775461	0.453878	0.063*
C18	1.0600 (5)	0.7792 (5)	0.2680 (4)	0.061 (2)
H18A	1.125533	0.790410	0.257413	0.073*
H18B	1.017123	0.777002	0.226584	0.073*
C16	0.8968 (5)	0.9029 (5)	0.3625 (4)	0.0578 (19)
H16A	0.876653	0.949941	0.330521	0.069*
H16B	0.945446	0.928241	0.395730	0.069*
C3	0.7294 (5)	0.6700 (5)	0.2179 (4)	0.0590 (19)
H3A	0.747298	0.724232	0.243136	0.071*
H3B	0.674802	0.684256	0.184983	0.071*
C10	0.8991 (5)	0.6225 (5)	0.4950 (3)	0.0553 (18)
H10A	0.909439	0.560824	0.510303	0.066*
H10B	0.888319	0.659487	0.532918	0.066*
C5	0.9834 (5)	0.6101 (6)	0.2012 (4)	0.062 (2)
H5A	0.991440	0.656283	0.168403	0.074*
H5B	0.980229	0.551744	0.179350	0.074*
C14	0.6405 (5)	0.8573 (5)	0.3732 (4)	0.061 (2)
H14A	0.588429	0.863464	0.337011	0.074*
H14B	0.638214	0.909355	0.402005	0.074*
C1	0.5754 (5)	0.6783 (5)	0.3143 (4)	0.0563 (18)
H1A	0.574059	0.734240	0.289300	0.068*
H1B	0.510513	0.667798	0.326374	0.068*
C19	0.8493 (6)	0.4487 (6)	0.3270 (5)	0.080 (3)
H19A	0.815558	0.458231	0.282869	0.096*
H19B	0.866206	0.507217	0.346411	0.096*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
I3	0.0500 (3)	0.0529 (3)	0.0579 (3)	0.0116 (2)	0.0208 (2)	0.0112 (2)
I6	0.0374 (2)	0.0686 (3)	0.0589 (3)	−0.0009 (2)	0.0123 (2)	−0.0057 (2)
I8	0.0663 (3)	0.0498 (3)	0.0490 (3)	0.0015 (2)	−0.0071 (2)	−0.0035 (2)
I1	0.0563 (3)	0.0793 (3)	0.0488 (3)	−0.0036 (2)	0.0133 (2)	0.0120 (2)
I5	0.0550 (3)	0.0809 (4)	0.0649 (3)	0.0043 (3)	0.0032 (2)	0.0090 (3)
I9	0.0566 (3)	0.0829 (4)	0.0709 (4)	0.0029 (3)	−0.0070 (3)	−0.0118 (3)
I2	0.0556 (3)	0.0782 (4)	0.0817 (4)	0.0073 (3)	0.0109 (3)	−0.0141 (3)
I4	0.0570 (3)	0.0763 (4)	0.0870 (4)	−0.0116 (3)	0.0080 (3)	0.0080 (3)
I7	0.0750 (4)	0.0988 (4)	0.0689 (4)	0.0195 (3)	0.0168 (3)	0.0200 (3)
Cl1	0.0651 (12)	0.0855 (15)	0.1010 (17)	0.0109 (11)	0.0239 (12)	−0.0196 (13)
Cl2	0.1055 (19)	0.0674 (14)	0.152 (3)	−0.0064 (13)	0.0815 (19)	−0.0079 (14)
O3	0.041 (2)	0.059 (3)	0.053 (3)	−0.004 (2)	0.008 (2)	−0.005 (2)
O4	0.039 (2)	0.067 (3)	0.046 (3)	0.003 (2)	0.009 (2)	0.006 (2)
O6	0.046 (3)	0.067 (3)	0.062 (3)	−0.010 (2)	0.017 (2)	−0.011 (2)
O5	0.045 (3)	0.051 (3)	0.072 (3)	−0.001 (2)	0.025 (2)	−0.004 (2)
O2	0.042 (3)	0.085 (4)	0.039 (3)	0.001 (2)	0.003 (2)	0.000 (2)
O1	0.048 (3)	0.067 (3)	0.057 (3)	0.012 (2)	0.010 (2)	0.000 (2)
N2	0.026 (2)	0.053 (3)	0.048 (3)	0.005 (2)	0.016 (2)	0.007 (3)
N1	0.033 (3)	0.038 (3)	0.056 (3)	−0.005 (2)	0.014 (2)	−0.011 (2)
C11	0.054 (4)	0.062 (4)	0.053 (4)	−0.002 (3)	0.023 (3)	0.008 (3)
C7	0.030 (3)	0.058 (4)	0.053 (4)	−0.003 (3)	0.004 (3)	0.007 (3)
C9	0.047 (4)	0.057 (4)	0.060 (5)	−0.006 (3)	0.000 (3)	−0.002 (4)
C2	0.049 (4)	0.077 (5)	0.056 (5)	−0.008 (4)	0.005 (3)	−0.017 (4)
C15	0.044 (4)	0.064 (4)	0.055 (4)	0.000 (3)	0.008 (3)	−0.008 (4)
C8	0.038 (4)	0.066 (5)	0.060 (5)	0.008 (3)	0.014 (3)	0.011 (4)
C12	0.048 (4)	0.046 (4)	0.075 (5)	−0.005 (3)	0.024 (4)	−0.005 (4)
C4	0.050 (4)	0.096 (6)	0.039 (4)	0.002 (4)	0.001 (3)	0.001 (4)
C6	0.047 (4)	0.064 (5)	0.061 (5)	0.003 (3)	0.017 (3)	−0.008 (4)
C17	0.060 (4)	0.044 (4)	0.085 (6)	−0.004 (3)	0.031 (4)	0.013 (4)
C13	0.050 (4)	0.047 (4)	0.065 (5)	−0.003 (3)	0.028 (3)	−0.015 (3)
C18	0.051 (4)	0.069 (5)	0.066 (5)	0.012 (4)	0.027 (4)	0.028 (4)
C16	0.051 (4)	0.043 (4)	0.080 (5)	−0.007 (3)	0.011 (4)	−0.003 (4)
C3	0.053 (4)	0.067 (5)	0.056 (5)	0.009 (4)	0.005 (3)	0.006 (4)
C10	0.056 (4)	0.067 (5)	0.044 (4)	0.003 (4)	0.011 (3)	0.006 (3)
C5	0.054 (4)	0.084 (6)	0.049 (4)	0.002 (4)	0.009 (3)	−0.005 (4)
C14	0.048 (4)	0.045 (4)	0.095 (6)	0.000 (3)	0.023 (4)	−0.011 (4)
C1	0.037 (3)	0.061 (4)	0.069 (5)	0.004 (3)	0.002 (3)	−0.016 (4)
C19	0.068 (5)	0.072 (5)	0.106 (7)	0.020 (4)	0.040 (5)	0.022 (5)

Geometric parameters (Å, º) top

I3—I2	2.9799 (8)	C2—H2A	0.9700
I3—I4	2.8629 (8)	C2—H2B	0.9700
I6—I5	2.8015 (8)	C2—C1	1.525 (9)
I6—I7	3.0952 (8)	C15—H15A	0.9700
I8—I9	2.8001 (8)	C15—H15B	0.9700
I8—I7	3.0940 (9)	C15—C16	1.487 (10)
I1—I1ⁱ	2.7595 (11)	C8—H8A	0.9700
Cl1—C19	1.741 (8)	C8—H8B	0.9700
Cl2—C19	1.747 (8)	C12—H12A	0.9700
O3—C9	1.415 (8)	C12—H12B	0.9700
O3—C8	1.431 (8)	C4—H4A	0.9700
O4—C11	1.421 (8)	C4—H4B	0.9700
O4—C10	1.428 (8)	C4—C3	1.497 (10)
O6—C15	1.408 (8)	C6—H6A	0.9700
O6—C14	1.429 (8)	C6—H6B	0.9700
O5—C17	1.421 (8)	C6—C5	1.503 (10)
O5—C16	1.403 (8)	C17—H17A	0.9700
O2—C4	1.426 (8)	C17—H17B	0.9700
O2—C5	1.430 (8)	C17—C18	1.497 (10)
O1—C2	1.402 (8)	C13—H13A	0.9700
O1—C3	1.422 (8)	C13—H13B	0.9700
N2—H2	0.84 (7)	C13—C14	1.500 (10)
N2—C7	1.495 (8)	C18—H18A	0.9700
N2—C6	1.500 (8)	C18—H18B	0.9700
N2—C18	1.506 (8)	C16—H16A	0.9700
N1—H1	0.83 (7)	C16—H16B	0.9700
N1—C12	1.493 (8)	C3—H3A	0.9700
N1—C13	1.507 (8)	C3—H3B	0.9700
N1—C1	1.495 (9)	C10—H10A	0.9700
C11—H11A	0.9700	C10—H10B	0.9700
C11—H11B	0.9700	C5—H5A	0.9700
C11—C12	1.505 (10)	C5—H5B	0.9700
C7—H7A	0.9700	C14—H14A	0.9700
C7—H7B	0.9700	C14—H14B	0.9700
C7—C8	1.500 (9)	C1—H1A	0.9700
C9—H9A	0.9700	C1—H1B	0.9700
C9—H9B	0.9700	C19—H19A	0.9700
C9—C10	1.497 (9)	C19—H19B	0.9700

I4—I3—I2	176.54 (2)	C3—C4—H4A	109.7
I5—I6—I7	173.63 (2)	C3—C4—H4B	109.7
I9—I8—I7	175.52 (2)	N2—C6—H6A	109.3
I8—I7—I6	89.70 (2)	N2—C6—H6B	109.3
C9—O3—C8	113.1 (5)	N2—C6—C5	111.5 (6)
C11—O4—C10	111.8 (5)	H6A—C6—H6B	108.0
C15—O6—C14	113.0 (6)	C5—C6—H6A	109.3
C16—O5—C17	111.9 (5)	C5—C6—H6B	109.3
C4—O2—C5	112.2 (5)	O5—C17—H17A	110.3
C2—O1—C3	114.9 (5)	O5—C17—H17B	110.3
C7—N2—H2	110 (5)	O5—C17—C18	107.3 (6)
C7—N2—C6	112.0 (5)	H17A—C17—H17B	108.5
C7—N2—C18	112.9 (5)	C18—C17—H17A	110.3
C6—N2—H2	106 (4)	C18—C17—H17B	110.3
C6—N2—C18	111.6 (6)	N1—C13—H13A	108.9
C18—N2—H2	104 (4)	N1—C13—H13B	108.9
C12—N1—H1	108 (5)	H13A—C13—H13B	107.7
C12—N1—C13	113.0 (5)	C14—C13—N1	113.6 (6)
C12—N1—C1	112.4 (5)	C14—C13—H13A	108.9
C13—N1—H1	111 (5)	C14—C13—H13B	108.9
C1—N1—H1	103 (5)	N2—C18—H18A	109.2
C1—N1—C13	109.8 (5)	N2—C18—H18B	109.2
O4—C11—H11A	110.3	C17—C18—N2	112.2 (6)
O4—C11—H11B	110.3	C17—C18—H18A	109.2
O4—C11—C12	107.0 (6)	C17—C18—H18B	109.2
H11A—C11—H11B	108.6	H18A—C18—H18B	107.9
C12—C11—H11A	110.3	O5—C16—C15	111.7 (6)
C12—C11—H11B	110.3	O5—C16—H16A	109.3
N2—C7—H7A	109.0	O5—C16—H16B	109.3
N2—C7—H7B	109.0	C15—C16—H16A	109.3
N2—C7—C8	113.0 (5)	C15—C16—H16B	109.3
H7A—C7—H7B	107.8	H16A—C16—H16B	107.9
C8—C7—H7A	109.0	O1—C3—C4	109.7 (6)
C8—C7—H7B	109.0	O1—C3—H3A	109.7
O3—C9—H9A	109.5	O1—C3—H3B	109.7
O3—C9—H9B	109.5	C4—C3—H3A	109.7
O3—C9—C10	110.7 (6)	C4—C3—H3B	109.7
H9A—C9—H9B	108.1	H3A—C3—H3B	108.2
C10—C9—H9A	109.5	O4—C10—C9	111.0 (5)
C10—C9—H9B	109.5	O4—C10—H10A	109.4
O1—C2—H2A	108.9	O4—C10—H10B	109.4
O1—C2—H2B	108.9	C9—C10—H10A	109.4
O1—C2—C1	113.1 (6)	C9—C10—H10B	109.4
H2A—C2—H2B	107.8	H10A—C10—H10B	108.0
C1—C2—H2A	108.9	O2—C5—C6	106.9 (6)
C1—C2—H2B	108.9	O2—C5—H5A	110.3
O6—C15—H15A	109.7	O2—C5—H5B	110.3
O6—C15—H15B	109.7	C6—C5—H5A	110.3
O6—C15—C16	110.0 (6)	C6—C5—H5B	110.3
H15A—C15—H15B	108.2	H5A—C5—H5B	108.6
C16—C15—H15A	109.7	O6—C14—C13	112.1 (6)
C16—C15—H15B	109.7	O6—C14—H14A	109.2
O3—C8—C7	111.7 (5)	O6—C14—H14B	109.2
O3—C8—H8A	109.3	C13—C14—H14A	109.2
O3—C8—H8B	109.3	C13—C14—H14B	109.2
C7—C8—H8A	109.3	H14A—C14—H14B	107.9
C7—C8—H8B	109.3	N1—C1—C2	111.9 (5)
H8A—C8—H8B	107.9	N1—C1—H1A	109.2
N1—C12—C11	112.8 (5)	N1—C1—H1B	109.2
N1—C12—H12A	109.0	C2—C1—H1A	109.2
N1—C12—H12B	109.0	C2—C1—H1B	109.2
C11—C12—H12A	109.0	H1A—C1—H1B	107.9
C11—C12—H12B	109.0	Cl1—C19—Cl2	110.7 (5)
H12A—C12—H12B	107.8	Cl1—C19—H19A	109.5
O2—C4—H4A	109.7	Cl1—C19—H19B	109.5
O2—C4—H4B	109.7	Cl2—C19—H19A	109.5
O2—C4—C3	109.7 (6)	Cl2—C19—H19B	109.5
H4A—C4—H4B	108.2	H19A—C19—H19B	108.1

O3—C9—C10—O4	−67.8 (7)	C12—N1—C1—C2	−62.5 (8)
O4—C11—C12—N1	−51.0 (7)	C4—O2—C5—C6	171.4 (6)
O6—C15—C16—O5	−72.6 (8)	C6—N2—C7—C8	−65.1 (7)
O5—C17—C18—N2	−52.5 (8)	C6—N2—C18—C17	167.7 (6)
O2—C4—C3—O1	−65.1 (8)	C17—O5—C16—C15	−169.0 (6)
O1—C2—C1—N1	−47.5 (9)	C13—N1—C12—C11	−65.1 (7)
N2—C7—C8—O3	−48.4 (8)	C13—N1—C1—C2	170.9 (6)
N2—C6—C5—O2	−43.6 (8)	C18—N2—C7—C8	167.9 (5)
N1—C13—C14—O6	−47.8 (9)	C18—N2—C6—C5	−62.6 (7)
C11—O4—C10—C9	−171.7 (6)	C16—O5—C17—C18	−172.5 (6)
C7—N2—C6—C5	169.8 (6)	C3—O1—C2—C1	−73.2 (8)
C7—N2—C18—C17	−65.1 (7)	C10—O4—C11—C12	−175.5 (6)
C9—O3—C8—C7	−77.9 (7)	C5—O2—C4—C3	−170.5 (6)
C2—O1—C3—C4	−150.6 (6)	C14—O6—C15—C16	−159.8 (6)
C15—O6—C14—C13	−75.9 (8)	C1—N1—C12—C11	170.0 (5)
C8—O3—C9—C10	−158.4 (5)	C1—N1—C13—C14	−64.4 (7)
C12—N1—C13—C14	169.3 (6)

Symmetry code: (i) −x+2, −y+1, −z.

Selected geometric parameters (Å, °) top

[Pd₂I₂([18]aneN₂S₄)](I)₂.(I₂)₅
Pd—I	2.5722 (14)	C6—S7	1.796 (10)
Pd—N1	2.076 (9)	S7—C8	1.816 (12)
Pd—S4	2.314 (3)	C8—C9	1.511 (16)
Pd—S7ⁱ	2.313 (3)	I—Iⁱⁱ	3.545 (2)
N1—C2	1.459 (15)	I1—I2	2.7899 (15)
N1—C9ⁱ	1.489 (16)	I2—I3	3.1214 (16)
C2—C3	1.514 (17)	I3—I4	3.205 (2)
C3—S4	1.809 (11)	I4—I5	2.7644 (16)
S4—C5	1.838 (10)	I3—I6	3.351 (3)
C5—C6	1.507 (15)	I6—I7	2.771 (4)
		I7—I3ⁱⁱⁱ	3.432 (3)

N1—Pd—S4	86.8 (3)	S7ⁱ—Pd—I	92.20 (8)
N1—Pd—S7ⁱ	87.7 (3)	S7ⁱ—Pd—S4	173.88 (11)
S4—Pd—I	93.57 (8)

[H₂([2.2.2]cryptand)](I₃)(I)(I₂)_2.5.CH₂Cl₂
I3—I2	2.9799 (8)	O1—C2	1.402 (8)
I3—I4	2.8629 (8)	O1—C3	1.422 (8)
I6—I5	2.8015 (8)	O2—C4	1.426 (8)
I6—I7	3.0952 (8)	O2—C5	1.430 (8)
I8—I9	2.8001 (8)	O3—C9	1.415 (8)
I8—I7	3.0940 (9)	O3—C8	1.431 (8)
I1—I1^iv	2.7595 (11)	O4—C11	1.421 (8)
N1—C1	1.495 (9)	O4—C10	1.428 (8)
N1—C12	1.493 (8)	O5—C17	1.421 (8)
N1—C13	1.507 (8)	O5—C16	1.403 (8)
N2—C6	1.500 (8)	O6—C15	1.408 (8)
N2—C7	1.495 (8)	O6—C14	1.429 (8)
N2—C18	1.506 (8)

I4—I3—I2	176.54 (2)	C3—C4—H4A	109.7
I5—I6—I7	173.63 (2)	C3—C4—H4B	109.7
I9—I8—I7	175.52 (2)	N2—C6—H6A	109.3
I8—I7—I6	89.70 (2)	N2—C6—H6B	109.3

Symmetry codes: (i) -x+3/2, -y+1/2, -z+1; (ii) -x+3/2, -y-1/2, -z+1; (iii) -x+1, y+1, -z+1/2; (iv) -x+2, -y+1, -z.

Acknowledgements

We thank Professor Francesco Demartin for useful discussions. We thank the University of Cagliari for financial support and the EPSRC (UK) for the award of X-ray diffractometers.

Data availability

The authors confirm that the data supporting the findings of this study are available within the article and its supplementary materials.

Funding information

The following funding is acknowledged: Engineering and Physical Sciences Research Council (grant Nos. GR/M54728/01 and GR/K45210/01).

References

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