Bis­(tetraethyl­ammonium) tetra­iodo­zincate at 150 and 301 K

The refinements described here for (NEt₄)[ZnI₄] completely confirm the results previously obtained for the isostructural tetra­bromo­cadmate at room temperature [Geselle & Fuess (1994). Acta Cryst. C50, 1582-1585]. Here again, isolated MX₄ (M = Zn and X = I) tetrahedra are accompanied by two cations in a `swastika' conformation and a third in a virtually planar trans conformation. One of the former cations is particularly disordered.

S1. Comment

A search of the Cambridge Structural Database (Allen & Kennard, 1993) by means of the CSSR component of the Chemical Database Service at Daresbury (Fletcher et al., 1996) strongly suggested that the present iodozincate was isostructural with the corresponding bromocadmate described by Geselle & Fuess (1994) (hereafter referenced as G&F). Indeed, adoption of the atomic coordinates as given by G&F led to a completely successful refinement of the iodozincate structure for data both at 301 and 150 K. In what follows, the data sets and the structural results derived from them are designated accordingly as 301 and 150 K.

G&F have already provided a detailed and virtually complete description of the isostructural room temperature form of bis(tetraethylammonium) tetrabromocadmate. Their general description applies equally to the tetraiodozincate structures, (I), described here. The same atom-labelling scheme has been used for both zincate structures and differs very little, if at all, from that used by G&F. Thus, once more rather regular and essentially isolated MX₄ tetrahedra (now M = Zn and X = I) are present in the structure. These are accompanied by three tetraethylammonium cations centred on N1, N2 and N3, respectively, and, for convenience, designated by number as 1, 2 and 3.

Adopting the nomenclature of G&F, the conformation of cations 1 and 2 may be described as swastika-like. This is particularly apparent when they are viewed down the fourfold axis. It is, however, to some extent misleading because this projection disguises the considerable height of the ions. Whereas cation 1 is comparatively ordered, cation 2 is not and appears as a superposed pair of mirror plane related and half-occupied species with N2, C4 and C6 in common. This disorder has implications for the placement of H in this cation as explained below. This disorder is, as expected, greater in the room-temperature (301 K) structure than in that at 150 K. Its effect is observable in the shortening of the N—C and C—C bonds of cation 2 compared with the other cations. Cation 3, described by G&F as interstitial in nature and trans in conformation, is much flatter. In effect, the methylene groups [C7, C9, C11 and C11ⁱ; symmetry code: (i) y + 1/2, x - 1/2, z] are ordered on either side of the virtually planar arrangement of N3, C8, C10, C12 and C12ⁱ.

For all of the structures mentioned here, the distribution of the ionic species may be represented as follows. The anions and the `interstitial' (G&F) cations 3 lie on either side of layers containing cations 1 and 2. A simple, if perhaps rather far-fetched, analogy might be the structures of the tetragonal oxides of divalent tin and lead (Wells, 1962). While the MX₄ anions and cations 1 and 2 correspond to M and O, respectively, of the tetragonal oxides cation 3 takes the place of the stereochemically active lone pair of the divalent metal atoms. Thus the MX₄ anions have five nearest neighbour cations in the form of a square (tetragonal) pyramid with cations 1 and 2 in the base and cation 3 at the apex. Conversely, whereas cations 1 and 2 have four nearest neighbour anions in a tetrahedral arrangement cation 3 has only one.

S2. Experimental

The title compound was isolated from reactions of bis(tetraethylammonium) Zn(DMIT)₂, where DMIT is the dianion of 1,3-dithiole-2-thione-4,5-dithiol, and a source of iodide [SbI₃ (150 K) or AsI₃ (301 K)] and recrystallized from ethanol on each occasion.

S3. Refinement

Refinements based on the coordinates of G&F proceeded smoothly and rapidly to the final conclusions presented here. The only difficulties encountered were in the placement and refinement of certain H atoms as described below. Twin refinement was found to be appropriate in the case of 301 K but not for 150 K. There were 1302 Friedel pairs in the 150 K data set and 1167 in the 301 K data set. Electron densities of magnitude greater than 1 e Å^-3 were observed in the final difference maps as maxima at 0.32 (150 K) and 1.38 Å (301 K) from Zn1 and in 150 K as a minimum 1.32 Å from I3. In general, H atoms were placed in geometrical positions and refined with a riding model. The disorder of cation 2 required the liberal application of SHELXL97 FREE instructions to accomplish this. For cation 3, while most of the H atoms were positioned by the normal geometrical processes, C8 and C10, methyl C with site symmetry m, were treated specially. For these, the H atoms were forced to satisfy the m site symmetry of the C to which they were attached, which may or may not actually be the case, in the following manner. The H atoms were placed with the AFIX 33 instruction thus preventing rotational refinement of the methyl groups. In addition, for each methyl group, manual intervention was used in order to enforce the relationship y = x - 1/2 for one H of the group and that the other two H had identical z coordinates. AFIX 33 was also used for the C6 methyl group of cation 2 of the 301 K structure because refinement of the rotational parameter proved to be extremely unstable. The occupancies of 0.5 presented along with the fractional atomic coordinates in the supplementary (CIF) data associated with this report are entirely appropriate in the case of the atoms C3, H3A—B, H4A—C, C5, H5A—B and H6A—C because they arise from the disorder of cation 2. This is not, however, the case for the H atom pairs H7A/B, H8B/C, H9A/B and H10B/C. Here, the individual atoms of each pair are related by the operation of a crystallographic mirror plane. Each such pair could then be represented equally well by one atom of the pair but with full occupancy. The pairwise half-occupied representation which has in fact been retained in the supplementary data might be regarded as an artefact arising from the mode of operation of the SHELXL97 AFIX instruction.

Computing details

Data collection: DENZO (Otwinowski & Minor, 1997) and COLLECT (Hooft, 1998) for 150K; SMART (Bruker, 1999) for 301K. Cell refinement: DENZO and COLLECT for 150K; SAINT (Bruker, 1999) for 301K. Data reduction: DENZO and COLLECT for 150K; SAINT (Bruker, 1999) for 301K. For both compounds, program(s) used to solve structure: starting parameters from G&F; program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

(150K) Bis(tetraethylammonium) tetraiodozincate

Crystal data

(C8H20N)2[ZnI4]	Dx = 1.994 Mg m^−3
Mr = 833.47	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P421m	Cell parameters from 10650 reflections
Hall symbol: P -4 2ab	θ = 2.0–26.4°
a = 13.6929 (5) Å	µ = 5.33 mm^−1
c = 14.8094 (6) Å	T = 150 K
V = 2776.70 (18) Å^3	Plate, colourless
Z = 4	0.25 × 0.10 × 0.05 mm
F(000) = 1568

Data collection

Enraf Nonius KappaCCD area-detector diffractometer	2989 independent reflections
Radiation source: Enraf Nonius FR591 rotating anode	2277 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.059
Detector resolution: 9.091 pixels mm^-1	θmax = 26.4°, θmin = 2.0°
ϕ–ω scans	h = −14→17
Absorption correction: empirical (using intensity measurements) (SORTAV; Blessing, 1997)	k = −17→13
Tmin = 0.536, Tmax = 0.766	l = −14→18
10650 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.048	H-atom parameters constrained
wR(F^2) = 0.122	Calculated w = 1/[σ^2(Fo^2) + (0.0663P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max = 0.002
2989 reflections	Δρmax = 1.64 e Å^−3
134 parameters	Δρmin = −1.18 e Å^−3
0 restraints	Absolute structure: Flack (1983)
Primary atom site location: heavy-atom method	Absolute structure parameter: −0.12 (7)

Special details

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. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

All of the structural entities (one anion and three cations) are in special positions with consequences for the atoms present in the asymmetric unit as follows.

Tetraiodozincate anion in 4 e - Zn (4 e), I1 (8f) and I2 and I3 (both 4 e).

Cation 1 in 2a - N1 (2a) and C1 and C2 (both in 8f).

Cation 2 in 2c - N2 (2c), C3 and C5 (disordered in 8f) and C4 and C6 (both 4 e). This cation appears as a disordered (equal occupancy) pair of superimposed mirror images with N2, C4 and C6 in common and hence fully occupied sites and both C3 and C5 and all ethyl H in mirror plane related and hence half- occupied sites. The atoms present in the asymmetric unit all belong to the same member of the pair and the disorder is only evident, therefore, in the partial occupancies and the bonds to N2.

Cation 3 in 4 e - N3 (4 e), C7 C8 C9 and C10 (all in 4 e) and C11 and C12 (8f).

In all cases H were placed in calculated positions (with liberal use of the SHELXL FREE instruction in the case of cation 2) and refined with a riding model. In the case of cation 3 H occur in pairs as H7A/B, H8B/C, H9A/B and H10B/C. The atoms of each such pair are related in symmetry by a crystallo- graphic mirror plane. Their sof of 0.5 can therefore be regarded as an artefact arising from the mode of operation of the SHELX AFIX instruction. Each such pair could, and perhaps should, be represented instead by one member of the pair in a fully occupied site. The SHELX representation has however been retained in the table of coordinates given below.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Zn1	0.74817 (6)	0.75183 (6)	0.72779 (9)	0.0296 (3)
I1	0.57097 (5)	0.70299 (6)	0.78002 (5)	0.0602 (2)
I2	0.87204 (5)	0.62796 (5)	0.79961 (6)	0.0531 (3)
I3	0.75496 (5)	0.74504 (5)	0.54989 (6)	0.0515 (3)
N1	0.5000	0.5000	0.5000	0.035 (3)
C1	0.5378 (8)	0.4172 (8)	0.5585 (8)	0.055 (3)
H1A	0.5647	0.3654	0.5191	0.066*
H1B	0.4825	0.3888	0.5927	0.066*
C2	0.6169 (8)	0.4495 (9)	0.6253 (7)	0.058 (3)
H2A	0.6759	0.4680	0.5920	0.087*
H2B	0.6320	0.3956	0.6665	0.087*
H2C	0.5933	0.5057	0.6601	0.087*
N2	1.0000	0.5000	0.4843 (12)	0.053 (5)
C3	0.9136 (15)	0.4894 (17)	0.5381 (13)	0.061 (6)	0.50
H3A	0.8582	0.4787	0.4962	0.074*	0.50
H3B	0.9019	0.5526	0.5687	0.074*	0.50
C4	0.9090 (8)	0.4090 (8)	0.6106 (12)	0.069 (5)
H4A	0.9384	0.3490	0.5869	0.104*	0.50
H4B	0.8407	0.3965	0.6267	0.104*	0.50
H4C	0.9449	0.4303	0.6643	0.104*	0.50
C5	1.010 (2)	0.4130 (19)	0.4239 (14)	0.080 (8)	0.50
H5A	0.9476	0.4052	0.3912	0.096*	0.50
H5B	1.0175	0.3549	0.4632	0.096*	0.50
C6	1.0907 (14)	0.4093 (14)	0.3549 (12)	0.120 (10)
H6A	1.1503	0.4374	0.3807	0.179*	0.50
H6B	1.0714	0.4468	0.3015	0.179*	0.50
H6C	1.1029	0.3413	0.3377	0.179*	0.50
N3	0.7906 (6)	0.2906 (6)	0.9214 (7)	0.040 (3)
C7	0.8344 (9)	0.3344 (9)	1.0059 (10)	0.061 (4)
H7A	0.7801	0.3622	1.0418	0.074*	0.50
H7B	0.8622	0.2801	1.0418	0.074*	0.50
C8	0.9100 (9)	0.4100 (9)	0.9987 (13)	0.090 (6)
H8A	0.9303	0.4304	1.0593	0.135*
H8B	0.8838	0.4664	0.9659	0.135*	0.50
H8C	0.9664	0.3838	0.9660	0.135*	0.50
C9	0.7133 (9)	0.2133 (9)	0.9492 (14)	0.076 (6)
H9A	0.7461	0.1638	0.9873	0.091*	0.50
H9B	0.6638	0.2461	0.9873	0.091*	0.50
C10	0.6602 (9)	0.1602 (9)	0.8738 (17)	0.099 (8)
H10A	0.6136	0.1136	0.8999	0.148*
H10B	0.7076	0.1249	0.8364	0.148*	0.50
H10C	0.6249	0.2076	0.8364	0.148*	0.50
C11	0.7393 (9)	0.3675 (9)	0.8657 (7)	0.061 (3)
H11A	0.7087	0.3350	0.8132	0.073*
H11B	0.7892	0.4131	0.8420	0.073*
C12	0.6608 (10)	0.4276 (10)	0.9139 (11)	0.084 (4)
H12A	0.6106	0.3838	0.9380	0.126*
H12B	0.6309	0.4732	0.8710	0.126*
H12C	0.6906	0.4644	0.9635	0.126*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Zn1	0.0324 (4)	0.0324 (4)	0.0240 (7)	−0.0017 (7)	−0.0010 (4)	0.0010 (4)
I1	0.0470 (4)	0.0836 (5)	0.0502 (4)	−0.0094 (4)	0.0022 (3)	−0.0177 (4)
I2	0.0566 (4)	0.0566 (4)	0.0462 (6)	0.0034 (5)	−0.0053 (3)	0.0053 (3)
I3	0.0578 (4)	0.0578 (4)	0.0389 (5)	−0.0010 (6)	−0.0040 (3)	0.0040 (3)
N1	0.039 (5)	0.039 (5)	0.027 (8)	0.000	0.000	0.000
C1	0.048 (6)	0.074 (7)	0.043 (6)	0.009 (6)	−0.004 (5)	0.013 (6)
C2	0.063 (7)	0.069 (7)	0.041 (6)	0.024 (6)	−0.007 (5)	−0.005 (5)
N2	0.048 (6)	0.048 (6)	0.063 (12)	−0.005 (8)	0.000	0.000
C3	0.060 (13)	0.065 (14)	0.060 (13)	−0.005 (11)	−0.001 (11)	0.022 (12)
C4	0.064 (7)	0.064 (7)	0.080 (12)	−0.014 (9)	−0.015 (6)	−0.015 (6)
C5	0.10 (2)	0.079 (17)	0.062 (14)	−0.032 (15)	0.013 (15)	−0.026 (13)
C6	0.150 (15)	0.150 (15)	0.058 (12)	−0.045 (19)	0.050 (11)	−0.050 (11)
N3	0.044 (4)	0.044 (4)	0.033 (6)	0.003 (5)	0.006 (4)	0.006 (4)
C7	0.073 (7)	0.073 (7)	0.039 (9)	0.015 (9)	−0.013 (6)	−0.013 (6)
C8	0.084 (8)	0.084 (8)	0.102 (15)	−0.015 (12)	−0.011 (9)	−0.011 (9)
C9	0.055 (6)	0.055 (6)	0.118 (16)	0.008 (8)	0.035 (8)	0.035 (8)
C10	0.060 (8)	0.060 (8)	0.18 (2)	−0.021 (10)	−0.023 (9)	−0.023 (9)
C11	0.084 (8)	0.056 (6)	0.044 (6)	0.006 (7)	−0.007 (6)	0.005 (5)
C12	0.076 (9)	0.058 (7)	0.117 (12)	0.012 (7)	−0.023 (8)	0.003 (8)

Geometric parameters (Å, º)

Zn1—I2	2.6240 (16)	N2—C5^vi	1.50 (2)
Zn1—I1	2.6331 (10)	N2—C5	1.50 (2)
Zn1—I1^i	2.6331 (10)	N2—C5^i	1.50 (2)
Zn1—I3	2.6379 (16)	N2—C5^v	1.50 (2)
N1—C1^ii	1.518 (10)	C3—C4	1.54 (2)
N1—C1^iii	1.518 (10)	C5—C6	1.50 (3)
N1—C1^iv	1.518 (10)	N3—C11	1.511 (11)
N1—C1	1.518 (10)	N3—C11^vi	1.511 (11)
C1—C2	1.532 (15)	N3—C7	1.512 (19)
N2—C3^v	1.43 (2)	N3—C9	1.55 (2)
N2—C3^i	1.43 (2)	C7—C8	1.47 (2)
N2—C3	1.43 (2)	C9—C10	1.52 (3)
N2—C3^vi	1.43 (2)	C11—C12	1.530 (17)
I2—Zn1—I1	108.20 (4)	C3^vi—N2—C5	71.6 (12)
I2—Zn1—I1^i	108.20 (4)	C5^vi—N2—C5	78 (2)
I1—Zn1—I1^i	112.45 (6)	C3^v—N2—C5^i	71.6 (12)
I2—Zn1—I3	111.06 (5)	C3^i—N2—C5^i	109.1 (13)
I1—Zn1—I3	108.48 (4)	C3—N2—C5^i	168.5 (15)
I1^i—Zn1—I3	108.48 (4)	C3^vi—N2—C5^i	109.6 (13)
C1^ii—N1—C1^iii	110.3 (9)	C5^vi—N2—C5^i	107 (2)
C1^ii—N1—C1^iv	109.0 (4)	C5—N2—C5^i	60 (2)
C1^iii—N1—C1^iv	109.0 (4)	C3^v—N2—C5^v	109.1 (13)
C1^ii—N1—C1	109.0 (4)	C3^i—N2—C5^v	71.6 (12)
C1^iii—N1—C1	109.0 (4)	C3—N2—C5^v	109.6 (13)
C1^iv—N1—C1	110.3 (9)	C3^vi—N2—C5^v	168.5 (15)
N1—C1—C2	113.2 (9)	C5^vi—N2—C5^v	60 (2)
C3^v—N2—C3^i	61.6 (18)	C5—N2—C5^v	107 (2)
C3^v—N2—C3	113 (2)	C5^i—N2—C5^v	78 (2)
C3^i—N2—C3	82 (2)	N2—C3—C4	119.6 (16)
C3^v—N2—C3^vi	82 (2)	N2—C5—C6	120.0 (18)
C3^i—N2—C3^vi	113 (2)	C11—N3—C11^vi	110.6 (11)
C3—N2—C3^vi	61.6 (18)	C11—N3—C7	111.1 (7)
C3^v—N2—C5^vi	168.5 (15)	C11^vi—N3—C7	111.1 (7)
C3^i—N2—C5^vi	109.6 (13)	C11—N3—C9	107.6 (9)
C3—N2—C5^vi	71.6 (12)	C11^vi—N3—C9	107.6 (9)
C3^vi—N2—C5^vi	109.1 (13)	C7—N3—C9	108.7 (12)
C3^v—N2—C5	109.6 (13)	C8—C7—N3	119.9 (15)
C3^i—N2—C5	168.5 (15)	C10—C9—N3	117.3 (16)
C3—N2—C5	109.1 (13)	N3—C11—C12	116.6 (9)
C1^ii—N1—C1—C2	−175.9 (9)	C3^vi—N2—C5—C6	−135 (3)
C1^iii—N1—C1—C2	63.6 (5)	C5^vi—N2—C5—C6	110 (2)
C1^iv—N1—C1—C2	−56.1 (7)	C5^i—N2—C5—C6	−8 (3)
C3^v—N2—C3—C4	−54.2 (14)	C5^v—N2—C5—C6	56.8 (19)
C3^i—N2—C3—C4	−108.8 (17)	C11—N3—C7—C8	−61.8 (8)
C3^vi—N2—C3—C4	12 (2)	C11^vi—N3—C7—C8	61.8 (8)
C5^vi—N2—C3—C4	137 (2)	C9—N3—C7—C8	180.000 (1)
C5—N2—C3—C4	68 (2)	C11—N3—C9—C10	59.6 (7)
C5^i—N2—C3—C4	55 (9)	C11^vi—N3—C9—C10	−59.6 (7)
C5^v—N2—C3—C4	−175.8 (17)	C7—N3—C9—C10	180.000 (1)
C3^v—N2—C5—C6	−61 (3)	C11^vi—N3—C11—C12	−178.6 (8)
C3^i—N2—C5—C6	−22 (10)	C7—N3—C11—C12	−54.7 (15)
C3—N2—C5—C6	175 (2)	C9—N3—C11—C12	64.2 (15)

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

(301K) bis(tetraethylammonium) tertraiodozincate

Crystal data

(C8H20N)2[ZnI4]	Dx = 1.946 Mg m^−3
Mr = 833.47	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P421m	Cell parameters from 4735 reflections
Hall symbol: P -4 2ab	θ = 2.5–21.7°
a = 13.8199 (6) Å	µ = 5.21 mm^−1
c = 14.8975 (7) Å	T = 301 K
V = 2845.3 (2) Å^3	Block, colourless
Z = 4	0.30 × 0.28 × 0.17 mm
F(000) = 1568

Data collection

Bruker SMART 1000 CCD diffractometer	2678 independent reflections
Radiation source: fine-focus sealed tube	1825 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.081
ϕ–ω scans	θmax = 25.0°, θmin = 1.4°
Absorption correction: multi-scan (SADABS; Sheldrick, 1997)	h = −16→16
Tmin = 0.196, Tmax = 0.413	k = −16→13
17580 measured reflections	l = −17→17

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.049	H-atom parameters constrained
wR(F^2) = 0.135	Calculated w = 1/[σ^2(Fo^2) + (0.0828P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.99	(Δ/σ)max < 0.001
2678 reflections	Δρmax = 1.39 e Å^−3
134 parameters	Δρmin = −0.67 e Å^−3
0 restraints	Absolute structure: Flack (1983)
Primary atom site location: heavy-atom method	Absolute structure parameter: 0.29 (9)

Special details

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. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

All of the structural entities (one anion and three cations) are in special positions with consequences for the atoms present in the asymmetric unit as follows.

Tetraiodozincate anion in 4 e - Zn (4 e), I1 (8f) and I2 and I3 (both 4 e).

Cation 1 in 2a - N1 (2a) and C1 and C2 (both in 8f).

Cation 2 in 2c - N2 (2c), C3 and C5 (disordered in 8f) and C4 and C6 (both 4 e). This cation appears as a disordered (equal occupancy) pair of superimposed mirror images with N2, C4 and C6 in common and hence fully occupied sites and both C3 and C5 and all ethyl H in mirror plane related and hence half- occupied sites. The atoms present in the asymmetric unit all belong to the same member of the pair and the disorder is only evident, therefore, in the partial occupancies and the bonds to N2.

Cation 3 in 4 e - N3 (4 e), C7 C8 C9 and C10 (all in 4 e) and C11 and C12 (8f).

In all cases H were placed in calculated positions (with liberal use of the SHELXL FREE instruction in the case of cation 2) and refined with a riding model. In the case of cation 3 H occur in pairs as H7A/B, H8B/C, H9A/B and H10B/C. The atoms of each such pair are related in symmetry by a crystallo- graphic mirror plane. Their sof of 0.5 can therefore be regarded as an artefact arising from the mode of operation of the SHELX AFIX instruction. Each such pair could, and perhaps should, be represented instead by one member of the pair in a fully occupied site. The SHELX representation has however been retained in the table of coordinates given below.

Note that TWIN/BASF twin refinement was applied to this structure and the Flack x parameter therefore represents the amount of the minor twin component.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Zn1	0.74758 (8)	0.75242 (8)	0.72848 (10)	0.0587 (4)
I1	0.57305 (6)	0.70492 (8)	0.78081 (7)	0.1031 (4)
I2	0.86988 (7)	0.63012 (7)	0.79847 (9)	0.0986 (4)
I3	0.75521 (7)	0.74479 (7)	0.55304 (7)	0.0839 (4)
N1	0.5000	0.5000	0.5000	0.060 (4)
C1	0.5387 (10)	0.4186 (11)	0.5571 (11)	0.093 (4)
H1A	0.5657	0.3691	0.5183	0.111*
H1B	0.4857	0.3899	0.5905	0.111*
C2	0.6178 (10)	0.4528 (12)	0.6240 (10)	0.102 (5)
H2A	0.6666	0.4884	0.5922	0.154*
H2B	0.6466	0.3975	0.6524	0.154*
H2C	0.5890	0.4936	0.6688	0.154*
N2	1.0000	0.5000	0.4804 (17)	0.085 (6)
C3	0.917 (2)	0.491 (2)	0.5421 (17)	0.111 (9)	0.50
H3A	0.8592	0.4865	0.5053	0.134*	0.50
H3B	0.9122	0.5520	0.5747	0.134*	0.50
C4	0.9116 (12)	0.4116 (12)	0.6103 (16)	0.121 (8)
H4A	0.9483	0.3570	0.5896	0.182*	0.50
H4B	0.8453	0.3928	0.6187	0.182*	0.50
H4C	0.9377	0.4340	0.6663	0.182*	0.50
C5	1.006 (2)	0.417 (2)	0.427 (2)	0.126 (11)	0.50
H5A	0.9484	0.4149	0.3904	0.151*	0.50
H5B	1.0040	0.3618	0.4670	0.151*	0.50
C6	1.0960 (18)	0.4040 (18)	0.3633 (16)	0.172 (14)
H6A	1.0891	0.3449	0.3301	0.258*	0.50
H6B	1.1542	0.4015	0.3985	0.258*	0.50
H6C	1.0994	0.4575	0.3223	0.258*	0.50
N3	0.7905 (6)	0.2905 (6)	0.9198 (8)	0.070 (3)
C7	0.8311 (17)	0.3311 (17)	1.0025 (17)	0.143 (10)
H7A	0.8587	0.2787	1.0374	0.171*	0.50
H7B	0.7787	0.3587	1.0374	0.171*	0.50
C8	0.9103 (13)	0.4103 (13)	0.989 (2)	0.182 (15)
H8A	0.9325	0.4325	1.0467	0.273*
H8B	0.8835	0.4637	0.9563	0.273*	0.50
H8C	0.9637	0.3835	0.9563	0.273*	0.50
C9	0.7152 (12)	0.2152 (12)	0.953 (2)	0.130 (9)
H9A	0.6671	0.2474	0.9898	0.156*	0.50
H9B	0.7474	0.1671	0.9898	0.156*	0.50
C10	0.6635 (13)	0.1635 (13)	0.871 (3)	0.188 (18)
H10A	0.6174	0.1174	0.8937	0.282*
H10B	0.7110	0.1308	0.8354	0.282*	0.50
H10C	0.6308	0.2110	0.8354	0.282*	0.50
C11	0.7409 (15)	0.3657 (14)	0.8653 (11)	0.134 (6)
H11A	0.7102	0.3343	0.8145	0.161*
H11B	0.7895	0.4095	0.8418	0.161*
C12	0.6639 (14)	0.4259 (14)	0.9151 (16)	0.143 (7)
H12A	0.6157	0.3835	0.9397	0.214*
H12B	0.6339	0.4701	0.8739	0.214*
H12C	0.6941	0.4616	0.9628	0.214*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Zn1	0.0580 (5)	0.0580 (5)	0.0600 (8)	−0.0039 (8)	0.0007 (6)	−0.0007 (6)
I1	0.0697 (5)	0.1427 (8)	0.0970 (6)	−0.0246 (5)	0.0116 (5)	−0.0327 (6)
I2	0.0974 (6)	0.0974 (6)	0.1008 (9)	0.0150 (7)	−0.0146 (5)	0.0146 (5)
I3	0.0908 (5)	0.0908 (5)	0.0699 (6)	−0.0074 (7)	−0.0038 (4)	0.0038 (4)
N1	0.062 (6)	0.062 (6)	0.054 (9)	0.000	0.000	0.000
C1	0.074 (8)	0.097 (9)	0.107 (10)	0.006 (7)	−0.004 (7)	0.008 (8)
C2	0.091 (10)	0.117 (11)	0.099 (10)	0.025 (8)	−0.032 (8)	0.005 (8)
N2	0.061 (7)	0.061 (7)	0.134 (19)	−0.016 (9)	0.000	0.000
C3	0.14 (3)	0.11 (2)	0.091 (18)	0.003 (19)	0.015 (19)	0.011 (17)
C4	0.112 (11)	0.112 (11)	0.14 (2)	−0.016 (15)	−0.015 (10)	−0.015 (10)
C5	0.15 (3)	0.12 (2)	0.11 (2)	0.00 (2)	0.00 (2)	−0.059 (19)
C6	0.21 (2)	0.21 (2)	0.096 (16)	−0.03 (3)	0.036 (16)	−0.036 (16)
N3	0.072 (5)	0.072 (5)	0.067 (8)	−0.018 (6)	0.002 (4)	0.002 (4)
C7	0.164 (16)	0.164 (16)	0.100 (17)	0.05 (2)	−0.024 (13)	−0.024 (13)
C8	0.131 (15)	0.131 (15)	0.28 (5)	−0.04 (2)	−0.032 (17)	−0.032 (17)
C9	0.099 (10)	0.099 (10)	0.19 (2)	−0.010 (12)	0.039 (12)	0.039 (12)
C10	0.094 (11)	0.094 (11)	0.38 (6)	−0.010 (13)	−0.045 (17)	−0.045 (17)
C11	0.167 (17)	0.128 (13)	0.107 (11)	−0.019 (14)	−0.029 (12)	0.046 (10)
C12	0.111 (13)	0.108 (12)	0.21 (2)	0.044 (11)	−0.020 (13)	0.024 (13)

Geometric parameters (Å, º)

Zn1—I2	2.608 (2)	N2—C3^i	1.48 (3)
Zn1—I3	2.6178 (18)	N2—C3	1.48 (3)
Zn1—I1^i	2.6185 (12)	N2—C3^vi	1.48 (3)
Zn1—I1	2.6185 (12)	N2—C3^v	1.48 (3)
N1—C1^ii	1.508 (14)	C3—C4	1.50 (3)
N1—C1^iii	1.508 (14)	C5—C6	1.58 (4)
N1—C1	1.508 (14)	N3—C7	1.47 (3)
N1—C1^iv	1.508 (14)	N3—C11^vi	1.486 (17)
C1—C2	1.55 (2)	N3—C11	1.486 (17)
N2—C5^v	1.39 (3)	N3—C9	1.55 (3)
N2—C5^vi	1.39 (3)	C7—C8	1.56 (4)
N2—C5	1.39 (3)	C9—C10	1.58 (4)
N2—C5^i	1.39 (3)	C11—C12	1.54 (2)
I2—Zn1—I3	110.30 (7)	C5^i—N2—C3	171 (2)
I2—Zn1—I1^i	108.39 (5)	C3^i—N2—C3	75 (3)
I3—Zn1—I1^i	108.92 (5)	C5^v—N2—C3^vi	171 (2)
I2—Zn1—I1	108.39 (5)	C5^vi—N2—C3^vi	109.6 (18)
I3—Zn1—I1	108.92 (5)	C5—N2—C3^vi	73.8 (19)
I1^i—Zn1—I1	111.92 (7)	C5^i—N2—C3^vi	111.9 (17)
C1^ii—N1—C1^iii	111.4 (12)	C3^i—N2—C3^vi	103 (3)
C1^ii—N1—C1	108.5 (6)	C3—N2—C3^vi	59 (2)
C1^iii—N1—C1	108.5 (6)	C5^v—N2—C3^v	109.6 (18)
C1^ii—N1—C1^iv	108.5 (6)	C5^vi—N2—C3^v	171 (2)
C1^iii—N1—C1^iv	108.5 (6)	C5—N2—C3^v	111.9 (17)
C1—N1—C1^iv	111.4 (12)	C5^i—N2—C3^v	73.8 (19)
N1—C1—C2	112.6 (11)	C3^i—N2—C3^v	59 (2)
C5^v—N2—C5^vi	65 (3)	C3—N2—C3^v	103 (3)
C5^v—N2—C5	111 (3)	C3^vi—N2—C3^v	75 (3)
C5^vi—N2—C5	77 (3)	N2—C3—C4	121 (2)
C5^v—N2—C5^i	77 (3)	N2—C5—C6	119 (3)
C5^vi—N2—C5^i	111 (3)	C7—N3—C11^vi	111.6 (12)
C5—N2—C5^i	65 (3)	C7—N3—C11	111.6 (12)
C5^v—N2—C3^i	73.8 (19)	C11^vi—N3—C11	110.3 (17)
C5^vi—N2—C3^i	111.9 (17)	C7—N3—C9	104.2 (18)
C5—N2—C3^i	171 (2)	C11^vi—N3—C9	109.5 (11)
C5^i—N2—C3^i	109.6 (18)	C11—N3—C9	109.5 (11)
C5^v—N2—C3	111.9 (17)	N3—C7—C8	115 (2)
C5^vi—N2—C3	73.8 (19)	N3—C9—C10	111 (2)
C5—N2—C3	109.6 (18)	N3—C11—C12	115.7 (13)
C1^ii—N1—C1—C2	63.3 (7)	C3^i—N2—C5—C6	−55 (17)
C1^iii—N1—C1—C2	−175.5 (13)	C3—N2—C5—C6	−173 (3)
C1^iv—N1—C1—C2	−56.1 (10)	C3^vi—N2—C5—C6	−125 (3)
C5^v—N2—C3—C4	−176 (2)	C3^v—N2—C5—C6	−60 (4)
C5^vi—N2—C3—C4	131 (3)	C11^vi—N3—C7—C8	62.0 (11)
C5—N2—C3—C4	61 (3)	C11—N3—C7—C8	−62.0 (11)
C5^i—N2—C3—C4	10 (17)	C9—N3—C7—C8	180.000 (2)
C3^i—N2—C3—C4	−111 (2)	C7—N3—C9—C10	180.000 (1)
C3^vi—N2—C3—C4	5 (3)	C11^vi—N3—C9—C10	−60.5 (11)
C3^v—N2—C3—C4	−58 (2)	C11—N3—C9—C10	60.5 (11)
C5^v—N2—C5—C6	63 (3)	C7—N3—C11—C12	−53 (2)
C5^vi—N2—C5—C6	119 (2)	C11^vi—N3—C11—C12	−177.5 (11)
C5^i—N2—C5—C6	−1 (4)	C9—N3—C11—C12	62 (2)

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