Secondary bonding in di-methyl-bis-(morpholine-4-carbodi-thio-ato-κ2S,S')tin(IV): crystal structure and Hirshfeld surface analysis.

The title compound, [Sn(CH3)2(C5H8NOS2)2], has the SnIV atom bound by two methyl groups which lie over the weaker Sn-S bonds formed by two asymmetrically chelating di-thio-carbamate ligands so that the coordination geometry is skew-trapezoidal bipyramidal. The most prominent feature of the mol-ecular packing are secondary Sn⋯S inter-actions [Sn⋯S = 3.5654 (7) Å] that lead to centrosymmetric dimers. These are connected into a three-dimensional architecture via methyl-ene-C-H⋯S and methyl-C-H⋯O(morpholino) inter-actions. The Sn⋯S inter-actions are clearly evident in the Hirshfeld surface analysis of the title compound along with a number of other inter-molecular contacts.

Chemical context

Both binary tin and organotin di­thio­carbamates, RSn(S2CNRR′) for n + m = 4, are well known to exhibit potential biological properties, e.g. anti-cancer (Ferreira et al., 2014 ▸), anti-fungal (Yu et al., 2014 ▸) and anti-microbial (Ferreira et al., 2012 ▸), as well to serve as useful mol­ecular precursors for the generation of ‘SnS’ nanomaterials (Kevin et al., 2015 ▸). The structural chemistry of this class of compound has also attracted considerable inter­est over the years owing to the occurrence of significant structural diversity observed in seemingly closely related compounds (Tiekink, 2008 ▸). As a case in point and related to the title compound, [Sn(CH3)2(C5H8NOS2)2] (I), reported herein, are the variations in mol­ecular structure observed for the diorganotin bis­(di­thio­carbamate)s as discussed in the recent literature (Muthalib et al., 2014 ▸; Mohamad et al., 2016 ▸, 2017 ▸). These R 2Sn(S2CNRR’)2 structures are known to adopt four distinct coordination geometries with the majority being skew-trapezoidal bipyramidal or octa­hedral, each based on C2S4 donor sets. Fewer examples are known for five-coordinate, trigonal–bipyramidal species, e.g. (t-Bu)2Sn(S2CNMe2)2 in which one di­thio­carbamate ligand is monodentate (Kim et al., 1987 ▸), and seven-coordinate, penta­gonal–bipyramidal, e.g. [MeOC(=O)CH2CH2]2Sn(S2CNMe)2 where the carbonyl-O atom of one Sn-bound organic substituent is also coordinating the tin atom (Ng et al., 1989 ▸). This last example is of inter­est as it demonstrates tin may in fact increase its coordination number by additional inter­actions. When additional inter­actions of this type occur inter­molecularly, they are termed secondary bonding or tetrel bonding as a Group IV element, tin, is involved (Alcock, 1972 ▸; Marín-Luna et al., 2016 ▸; Tiekink, 2017 ▸). Generally, secondary inter­actions do not occur for R 2Sn(S2CNRR’)2 structures as the strong chelating ability of the di­thio­carbamate ligand reduces the Lewis acidity of the tin atom. However, in (I) such secondary Sn⋯S inter­actions do in fact occur. In a continuation of work in this area, herein the synthesis and crystal and mol­ecular structures of (I) are described as well as an analysis of the Hirshfeld surface with a particular emphasis on investigating the role of the secondary Sn⋯S inter­action.

Structural commentary

The SnIV atom in the title compound (I), Fig. 1 ▸, adopts one of the common coordination geometries found for R 2Sn(S2CNRR’)2 mol­ecules, i.e. skew-trapezoidal bipyramidal rather than octa­hedral (Tiekink, 2008 ▸). This arises as the chelating di­thio­carbamate ligands have asymmetric Sn—S bond lengths, Table 1 ▸. The values of Δ(Sn—S) = [d(Sn—Slong) − d(Sn—Sshort] for the S1- and S3-di­thio­carbamate ligands are approximately the same at 0.35 Å, but the comparable bonds formed by the S3-di­thio­carbamate ligand are systematically longer than those formed by the S1-di­thio­carbamate ligand by approximately 0.02 Å, Table 1 ▸. The asymmetry in the Sn—S bond lengths is reflected in the disparity in the associated C—S bond lengths with the sulfur atom forming the longer Sn—S bond being involved in the significantly shorter, by approx­imately 0.05 Å, C—S bond, Table 1 ▸. Consistent with the skew-trapezoidal bipyramidal geometry about the SnIV atom, the Sn-bound methyl substituents are directed over the longer Sn—S bonds and define an angle of 148.24 (11)° at the tin atom. The angle subtended at the tin atom by the strongly bound sulfur atoms of 85.878 (19)° is significantly less than that formed by the weakly bound sulfur atoms, i.e. 143.066 (18)°, and is largely responsible for the formation of the skew-trapezoidal plane about the tin atom.

Figure 1

The mol­ecular structure of (I), showing the atom-labelling scheme and displacement ellipsoids at the 50% probability level.

Table 1

Selected geometric parameters (Å, °)

Sn—S1	2.5429 (6)	Sn—C12	2.111 (3)
Sn—S2	2.8923 (6)	C1—S1	1.747 (3)
Sn—S3	2.5649 (7)	C1—S2	1.702 (3)
Sn—S4	2.9137 (6)	C6—S3	1.750 (3)
Sn—C11	2.132 (3)	C6—S4	1.697 (3)
S1—Sn—S2	65.935 (19)	S2—Sn—C12	84.93 (8)
S1—Sn—S3	85.878 (19)	S3—Sn—S4	65.137 (18)
S1—Sn—S4	150.95 (2)	S3—Sn—C12	102.37 (8)
S1—Sn—C11	99.49 (8)	S3—Sn—C11	99.28 (8)
S1—Sn—C12	104.96 (8)	S4—Sn—C11	84.20 (8)
S2—Sn—S3	151.798 (18)	S4—Sn—C12	84.15 (7)
S2—Sn—S4	143.066 (18)	C11—Sn—C12	148.24 (11)
S2—Sn—C11	86.87 (8)

Supra­molecular features

An inter­esting feature of the mol­ecular packing in (I) is the formation of a supra­molecular dimer sustained by Sn⋯S secondary inter­actions, as shown in Fig. 2 ▸ a, where two long edges of the translationally displaced trapezoidal planes approach each other to form the inter­actions. Here, Sn⋯S4i is 3.5654 (7) Å, which is approximately 0.4 Å shorter than the sum of the van der Waals radii of Sn and S of 3.97 Å (Bondi, 1964 ▸); symmetry operation (i): 1 − x, 1 − y, 1 − z. Connections between the dimeric aggregates are of the type methyl­ene-C—H⋯S and methyl-C—H⋯O(morpholino), Table 2 ▸, and these inter­actions combine to generate a three-dimensional architecture, Fig. 2 ▸ b.

Figure 2

The mol­ecular packing in (I), showing (a) a supra­molecular dimer sustained by Sn⋯S secondary inter­actions shown as black dashed lines and (b) a view of the unit-cell contents in projection down the a axis. The C—H⋯S and C—H⋯O inter­actions are shown as orange and blue dashed lines, respectively.

Table 2

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C10—H10A⋯S1i	0.99	2.86	3.809 (3)	161
C12—H12C⋯O1ii	0.98	2.47	3.399 (4)	158

Symmetry codes: (i) ; (ii) .

Hirshfeld surface analysis

The Hirshfeld surfaces calculated on the structure of (I) also provide insight into the supra­molecular association through secondary Sn⋯S, S⋯S and other contacts, and was performed as per recent publications on related organotin di­thio­carbamate structures (Mohamad et al., 2017 ▸, 2016 ▸). The broad, bright-red spots appearing near the Sn and S4 atoms on the Hirshfeld surfaces mapped over d norm in Fig. 3 ▸ a indicate the formation of the supra­molecular dimer through secondary Sn⋯S contacts. On the Hirshfeld surface mapped over electrostatic potential in Fig. 4 ▸, these inter­actions are represented by the blue and red regions around these atoms, respectively. The faint-red spot appearing between the above bright-red spots near the S4 atom indicates the short inter-atomic S⋯S contact, Table 3 ▸, between S4 atoms lying on diagonally opposite vertices of a parallelogram formed by symmetry-related Sn and S4 atoms, Fig. 5 ▸ a. The pair of bright-red spots appearing near the methyl-H12C and morpholine-O1 atoms in Fig. 3 ▸ b represent the respective donor and acceptor atoms of the C12—H⋯O1 inter­action. The comparatively weaker methyl­ene-C10—H⋯S1 inter­action is viewed as a pair of faint-red spots near these atoms in Fig. 3 ▸ b. It is important to note from the immediate environments about a reference mol­ecule within d norm-mapped Hirshfeld surfaces highlighting inter­molecular inter­actions in Fig. 5 ▸ that the secondary Sn⋯S and S⋯S contacts are on one side of the Hirshfeld surface while the atoms participating in C—H⋯O and C—H⋯S inter­actions are on the other side of the surface.

Figure 3

Two views of the Hirshfeld surface for (I) plotted over d norm in the range −0.050 to 1.780 au.

Figure 4

A view of Hirshfeld surface for (I) mapped over the calculated electrostatic potential in the range −0.053 to +0.078 au. The red and blue regions represent negative and positive electrostatic potentials, respectively.

Table 3

Summary of short inter-atomic contacts (Å) in (I)

Contact	distance	symmetry operation
S4⋯S4	3.5835 (10)	1 − x, 1 − y, −z
S2⋯H12B	2.99	− x,  + y,  − z
S3⋯H5B	2.94	1 − x, 1 − y, 1 − z
S4⋯H11C	2.94	1 − x, 1 − y, − z
O2⋯H2A	2.63	− x, − + y,  − z
O2⋯H5B	2.70	− x, − + y,  − z
C1⋯H3A	2.88	2 − x, 1 − y, 1 − z
C3⋯H12C	2.86	2 − x, 1 − y, 1 − z
H2A⋯H11C	2.36	+ x,  − y,  + z

Figure 5

Views of Hirshfeld surfaces mapped over d norm about a reference mol­ecule showing (a) secondary Sn⋯S/S⋯Sn and S⋯S contacts by sky-blue and red dashed lines, respectively and (b) C—H⋯O and C—H⋯S inter­actions by black dashed lines

The overall two-dimensional fingerprint plot, Fig. 6 ▸ a, and those delineated into H⋯H, S⋯H/H⋯S, O⋯H/H⋯O, C⋯H/H⋯C, N⋯H/H⋯N, Sn⋯S/S⋯Sn and S⋯S contacts (McKinnon et al., 2007 ▸) are illustrated in Fig. 6 ▸ b–h, respectively; the relative contributions from the various contacts to the Hirshfeld surfaces are summarized in Table 4 ▸.

Figure 6

(a) The full two-dimensional fingerprint plot for (I) and fingerprint plots delineated into (b) H⋯H, (c) S⋯H/H⋯S, (d) O⋯H/H⋯O, (e) C⋯H/H⋯C, (f) N⋯H/H⋯H, (g) Sn⋯S/S⋯Sn and (h) S⋯S contacts.

Table 4

Percentage contributions of inter-atomic contacts to the Hirshfeld surfaces for (I)

Contact	percentage contribution
H⋯H	56.8
S⋯H/H⋯S	27.2
O⋯H/H⋯O	9.9
C⋯/H⋯C	4.0
N⋯H/H⋯N	1.1
Sn⋯S/S⋯Sn	0.5
S⋯S	0.5

In the fingerprint plot delineated into H⋯H contacts, Fig. 6 ▸ b, the points forming the single short peak at d e + d i < 2.4 Å are indicative of the short inter-atomic H⋯H contact listed in Table 3 ▸. The involvement of S1 in the C—H⋯S inter­action and other sulfur atoms in short inter-atomic S⋯H/H⋯S contacts, Table 3 ▸, results in an overall 27.2% contribution to the Hirshfeld surface. In the fingerprint plot delineated into S⋯H/H⋯S contacts, Fig. 6 ▸ c, they appear as overlapping donor–acceptor regions showing corners and a pair of greenish regions of greater intensity having short spikes at d e + d i ∼ 2.9 Å. The C—H⋯O contact is evident from the two-dimensional fingerprint plot delineated into O⋯H/H⋯O contacts, Fig. 6 ▸ d, as the pair of tips at d e + d i ∼ 2.5 Å in the forceps-like distribution. The short inter-atomic O⋯H/H⋯O contacts, Table 3 ▸, in the plot appear as faint-green points in a slightly scattered form emanating from d e + d i ∼ 2.9 Å. The pair of short spikes at d e + d i < 2.9 Å overlapping on the well separated donor and acceptor regions in the fingerprint plot delineated into C⋯H/H⋯C contacts, Fig. 6 ▸ e, indicate the influence of short inter-atomic C⋯H/H⋯C contacts, Table 3 ▸. The presence of secondary Sn⋯S and short S⋯S contacts in the structure is also confirmed from the respective plots through the distribution of points as a pair of thin line segments, Fig. 6 ▸ f, and a triangle, Fig. 6 ▸ g, respectively, having minimum d e + d i distances at around 3.5 Å and 3.6 Å, respectively. The 1.1% contribution from N⋯H/H⋯N contacts, Fig. 6 ▸ h, to the Hirshfeld surface reflects an insignificant influence upon the mol­ecular packing as the inter-atomic separations are greater than the sum of the respective van der Waals radii.

Database survey

The Cambridge Crystallographic Database (Groom et al., 2016 ▸) contains over 110 mol­ecules of the general formula R 2Sn(S2CNRR’)2. Of these, 12 feature secondary Sn⋯S inter­actions which, with (I), means approximately 10% of all R 2Sn(S2CNRR’)2 structures have Sn⋯S secondary inter­actions. Selected geometric details for the 13 structures are collated in Table 5 ▸. The Sn⋯S inter­actions assemble mol­ecules in their crystals into three distinct structural motifs. The common motif, A, is a dimeric aggregate disposed about a centre of inversion, as is in (I), and is found in the majority of crystals, i.e. nine. This motif is illustrated in Fig. 7 ▸ a for (PhCH2)2Sn(S2CNEt2)2 (Yin et al., 2003 ▸). A second zero-dimensional motif, B, is also known and is readily related to A. In the structure of Me2Sn(S2CN(Et)CH2C6H4N-4)2 (Barba et al., 2012 ▸), two independent mol­ecules comprise the asymmetric unit. One of these self-assembles about a centre of inversion as for motif A. The nitro­gen atom of each pendent 4-pyridyl group of the dimeric aggregate thus assembled inter­acts with the tin atom of the second independent mol­ecule via a Sn⋯N inter­action to form the four-mol­ecule aggregate shown in Fig. 7 ▸ b. The final three mol­ecules are binuclear owing to the presence of bis­(di­thio­carbamate) ligands and self-assemble into supra­molecular chains. In {Me2SnS2CN(CH2Ph)CH2(1,3-C6H3)CH2(PhCH2)NCS2SnMe2}2 (Santacruz-Juárez et al., 2008 ▸), the mol­ecule is situated about a centre of inversion and each tin atom forms an Sn⋯S contact to generate a linear, supra­molecular chain, motif C, Fig. 7 ▸ c. A variation is seen in the crystal of Me2SnS2CN(CH2CH2-i-Pr)CH2(1,3-C6H3)CH2(PhCH2)NCS2SnMe2}2, where there are two independent, centrosymmetric mol­ecules in the asymmetric unit. Here, the resulting supra­molecular chain is twisted (Santacruz-Juárez et al., 2008 ▸) and is assigned as motif C′.

Table 5

Summary of Sn—S, Sn⋯S distances (Å) in R 2Sn(S2CNRR′)2 structures featuring secondary Sn⋯S inter­actions

R	R, R′	Sn—Sshort, Sn—Slong	Sn⋯S	motif	Reference
Me	Et, Et	2.5174 (18), 2.961 (3); 2.528 (2), 2.9162 (17)	3.853 (2)	A	Morris & Schlemper (1979 ▸)
Me	(CH2CH2)Me	2.5367 (14), 2.9171 (16); 2.5577 (15), 2.8953 (16)	3.6978 (18)	A	Zia-ur-Rehman et al. (2007 ▸)
Me	(CH2CH2)O	2.5429 (6), 2.8923 (6); 2.5649 (7), 2.9137 (6)	3.5654 (7)	A	this work
C(H)=CH2	Cy	2.514 (5), 2.914 (4); 2.536 (4), 2.914 (4)	3.662 (5)	A	Hall & Tiekink (1998 ▸)
CH2Ph	Et, Et	2.5310 (11), 2.8940 (11); 2.5396 (10), 2.9109 (11)	3.8161 (12)	A	Yin et al. (2003 ▸)
CH2PhCl-2	(CH2CH2)NMe	2.5401 (13), 2.8050 (13); 2.5675 (13), 2.8675 (12)	3.9071 (13)	A	Yin & Xue (2005a ▸)
CH2PhCl-3a	(CH2CH2)NEt	2.520 (3), 2.840 (3); 2.556 (2), 2.893 (3)	3.638 (3)	A	Xue et al. (2005 ▸)
CH2PhCl-4	(CH2CH2)NMe	2.534 (2), 2.968 (3); 2.550 (2), 2.858 (3)	3.765 (3)	A	Yin & Xue (2005b ▸)
CH2PhCN-4	Et, Et	2.524 (3), 2.885 (3); 2.537 (2), 2.879 (2)	3.821 (3)	A	Yin & Xue (2006 ▸)
Meb	Et; CH2Ph	2.543 (2), 2.943 (2); 2.549 (2), 2.909 (2)	3.724 (3)	B	Barba et al. (2012 ▸)
		2.579 (2), 2.842 (2); 2.609 (2), 3.003 (2)	2.978 (5)c
Med	CH2Ph, 0.5(1,3-CH2C6H4CH2)	2.5086 (13), 2.8791 (15); 2.5217 (14), 3.1510 (16)	3.9641 (15)	C	Santacruz-Juárez et al. (2008 ▸)
Med,e	bi­cyclo­[2.2.1]hept-2yl, 0.5(CH2)4	2.5179 (12), 2.9015 (13); 2.5321 (12), 2.9600 (13)	3.9453 (14)	C	Rojas-León et al. (2012 ▸)
Mef	(CH2)2 iPr, 0.5(1,3-CH2C6H4CH2)	2.5319 (18), 2.8855 (18); 2.5356 (17), 2.9663 (19)	4.0480 (19)	C′	Santacruz-Juárez et al. (2008 ▸)
		2.5306 (17), 2.9492 (19); 2.5402 (19), 2.9633 (19)	3.7050 (17)

Notes: (a) piperazine mono-solvate; (b) two mol­ecules in the asymmetric unit; (c) Sn⋯N secondary inter­action; (d) the binuclear mol­ecule is located about a centre of inversion; (e) CDCl3 di-solvate per binuclear entity; (f) two mol­ecules in the asymmetric unit with each being located about a centre of inversion.

Figure 7

Supra­molecular aggregation sustained by secondary Sn⋯S inter­actions (black dashed lines) leading to (a) dimeric aggregates in (PhCH2)2Sn(S2CNEt2)2, (b) four-mol­ecule aggregates in Me2Sn(S2CN(Et)CH2C6H4N-4)2 and (c) linear supra­molecular chain in {Me2SnS2CN(CH2Ph)CH2(1,3-C6H3)CH2(PhCH2)NCS2SnMe2}2.

The common feature of all motifs listed in Table 5 ▸ is that it is one of the weakly bound sulfur atoms that forms the secondary Sn⋯S inter­action. Further, the tin-bound groups are relatively sterically unencumbered, allowing for the close approach of sulfur donors to the tin atoms. There are no geometric correlations. However, reflecting the weak nature of these inter­actions, the sulfur atom forming the Sn⋯S contact does not necessarily form the weaker of the Sn—Slong inter­actions in each mol­ecule. The range of Sn⋯S distances spans nearly 0.5 Å but, again, no correlations between these distances and the Slong—Sn—Slong angles is apparent, i.e. it might be expected that the shorter Sn⋯S inter­actions would result in wider Slong—Sn—Slong angles.

Synthesis and crystallization

All chemicals and solvents were used as purchased without purification, and all reactions were carried out under ambient conditions. The melting point was determined using an Electrothermal digital melting point apparatus and was uncorrected. The IR spectrum for (I) was obtained on a Perkin Elmer Spectrum 400 FT Mid-IR/Far-IR spectrophotometer in the range 4000 to 400 cm−1. The 1H NMR spectrum was recorded at room temperature in CDCl3 solution on a Jeol ECA 400 MHz FT–NMR spectrometer.

Sodium morpholine­dithio­carbamate (prepared from the reaction between carbon di­sulfide and morpholine (Merck) in the presence of sodium hydroxide; 1.0 mmol, 0.185 g) in methanol (20 ml) was added to di­methyl­tin dichloride (Merck, 1.0 mmol, 0.219 g) in methanol (10 ml). The resulting mixture was stirred and refluxed for 2 h. The filtrate was evaporated until an off-white precipitate was obtained. The precipitate was recrystallized from methanol solution by slow evaporation to yield colourless prisms. Yield: 0.305 g, 64.4%; m.p.: 448 K. IR (cm−1): 1465(s), 1423(s) ν(C—N), 1222(s) ν(C—O), 1110(m), 994(s) ν(C—S), 541(m) ν(Sn—C) cm−1. 1H NMR (CDCl3): 4.18 (s, 8H, CH2O), 3.77 (s, 8H, NCH2), 1.54 (s, 6H, -CH3).

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 6 ▸. Carbon-bound H atoms were placed in calculated positions (C—H = 0.98–0.99 Å) and were included in the refinement in the riding-model approximation, with U iso(H) set to 1.2–1.5U eq(C). Owing to poor agreement, one reflection, i.e. ( 1 5), was omitted from the final cycles of refinement.

Table 6

Experimental details

Crystal data
Chemical formula	[Sn(CH3)2(C5H8NOS2)2]
M r	473.24
Crystal system, space group	Monoclinic, P21/n
Temperature (K)	100
a, b, c (Å)	10.1472 (1), 13.6653 (1), 13.8122 (1)
β (°)	104.959 (1)
V (Å3)	1850.36 (3)
Z	4
Radiation type	Cu Kα
μ (mm−1)	15.25
Crystal size (mm)	0.24 × 0.09 × 0.06
Data collection
Diffractometer	Agilent SuperNova, Dual, Cu at zero, AtlasS2
Absorption correction	Gaussian (CrysAlis PRO; Rigaku Oxford Diffraction, 2015 ▸)
T min, T max	0.242, 0.759
No. of measured, independent and observed [I > 2σ(I)] reflections	19588, 3865, 3809
R int	0.031
(sin θ/λ)max (Å−1)	0.631
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.024, 0.065, 1.07
No. of reflections	3865
No. of parameters	192
H-atom treatment	H-atom parameters constrained
Δρmax, Δρmin (e Å−3)	0.45, −0.50

Computer programs: CrysAlis PRO (Rigaku Oxford Diffraction, 2015 ▸), SHELXS (Sheldrick, 2008 ▸), SHELXL2014 (Sheldrick, 2015 ▸), ORTEP-3 for Windows (Farrugia, 2012 ▸), DIAMOND (Brandenburg, 2006 ▸) and publCIF (Westrip, 2010 ▸).

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S2056989017006855/hb7675sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989017006855/hb7675Isup2.hkl

CCDC reference: 1548414

Additional supporting information: crystallographic information; 3D view; checkCIF report

[Sn(CH3)2(C5H8NOS2)2]	F(000) = 952
Mr = 473.24	Dx = 1.699 Mg m−3
Monoclinic, P21/n	Cu Kα radiation, λ = 1.54184 Å
a = 10.1472 (1) Å	Cell parameters from 14936 reflections
b = 13.6653 (1) Å	θ = 3.2–76.6°
c = 13.8122 (1) Å	µ = 15.25 mm−1
β = 104.959 (1)°	T = 100 K
V = 1850.36 (3) Å3	Prism, colourless
Z = 4	0.24 × 0.09 × 0.06 mm

Agilent SuperNova, Dual, Cu at zero, AtlasS2 diffractometer	3865 independent reflections
Radiation source: micro-focus sealed X-ray tube, SuperNova (Cu) X-ray Source	3809 reflections with I > 2σ(I)
Mirror monochromator	Rint = 0.031
ω scans	θmax = 76.8°, θmin = 4.6°
Absorption correction: gaussian (CrysAlis PRO; Rigaku Oxford Diffraction, 2015)	h = −12→12
Tmin = 0.242, Tmax = 0.759	k = −13→17
19588 measured reflections	l = −17→17

Refinement on F2	0 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.024	H-atom parameters constrained
wR(F2) = 0.065	w = 1/[σ2(Fo2) + (0.0322P)2 + 2.5554P] where P = (Fo2 + 2Fc2)/3
S = 1.07	(Δ/σ)max = 0.001
3865 reflections	Δρmax = 0.45 e Å−3
192 parameters	Δρmin = −0.50 e Å−3

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.

	x	y	z	Uiso*/Ueq
Sn	0.54609 (2)	0.47196 (2)	0.20083 (2)	0.01811 (6)
S1	0.60114 (7)	0.47340 (5)	0.39117 (5)	0.02266 (14)
S2	0.76105 (7)	0.60660 (4)	0.29478 (4)	0.02164 (13)
S3	0.36959 (7)	0.34005 (5)	0.20926 (4)	0.02368 (13)
S4	0.38512 (7)	0.40224 (5)	0.00694 (4)	0.02491 (14)
O1	0.9722 (2)	0.62761 (17)	0.68544 (15)	0.0315 (4)
O2	−0.1073 (2)	0.28893 (17)	−0.02186 (16)	0.0334 (5)
N1	0.7980 (2)	0.59004 (16)	0.49256 (16)	0.0216 (4)
N2	0.1802 (2)	0.29886 (17)	0.04134 (16)	0.0235 (5)
C1	0.7294 (3)	0.56096 (18)	0.40120 (18)	0.0188 (5)
C2	0.8983 (3)	0.6702 (2)	0.5084 (2)	0.0245 (5)
H2A	0.8543	0.7321	0.5205	0.029*
H2B	0.9318	0.6786	0.4477	0.029*
C3	1.0169 (3)	0.6474 (2)	0.5975 (2)	0.0294 (6)
H3A	1.0670	0.5899	0.5817	0.035*
H3B	1.0805	0.7036	0.6103	0.035*
C4	0.8853 (3)	0.5444 (2)	0.6688 (2)	0.0285 (6)
H4A	0.8579	0.5290	0.7309	0.034*
H4B	0.9355	0.4874	0.6522	0.034*
C5	0.7594 (3)	0.5622 (2)	0.58459 (19)	0.0253 (5)
H5A	0.7031	0.5021	0.5722	0.030*
H5B	0.7044	0.6151	0.6037	0.030*
C6	0.2990 (3)	0.34278 (18)	0.07953 (18)	0.0202 (5)
C7	0.1020 (3)	0.2459 (2)	0.1005 (2)	0.0267 (6)
H7A	0.1494	0.2502	0.1726	0.032*
H7B	0.0943	0.1760	0.0810	0.032*
C8	−0.0379 (3)	0.2905 (2)	0.0819 (2)	0.0310 (6)
H8A	−0.0919	0.2539	0.1201	0.037*
H8B	−0.0296	0.3590	0.1061	0.037*
C9	−0.0330 (3)	0.3430 (2)	−0.0777 (2)	0.0303 (6)
H9A	−0.0261	0.4120	−0.0551	0.036*
H9B	−0.0829	0.3418	−0.1495	0.036*
C10	0.1087 (3)	0.3021 (2)	−0.06570 (19)	0.0249 (5)
H10A	0.1028	0.2354	−0.0945	0.030*
H10B	0.1599	0.3439	−0.1020	0.030*
C11	0.4147 (3)	0.5961 (2)	0.1692 (2)	0.0260 (5)
H11A	0.4573	0.6513	0.2110	0.039*
H11B	0.3275	0.5803	0.1837	0.039*
H11C	0.3987	0.6137	0.0983	0.039*
C12	0.7041 (3)	0.38945 (19)	0.1667 (2)	0.0242 (5)
H12A	0.7154	0.4095	0.1012	0.036*
H12B	0.6809	0.3197	0.1650	0.036*
H12C	0.7894	0.4008	0.2181	0.036*

	U11	U22	U33	U12	U13	U23
Sn	0.02190 (10)	0.01935 (10)	0.01260 (9)	0.00090 (6)	0.00357 (6)	−0.00052 (5)
S1	0.0275 (3)	0.0258 (3)	0.0140 (3)	−0.0074 (2)	0.0041 (2)	−0.0009 (2)
S2	0.0290 (3)	0.0213 (3)	0.0154 (3)	−0.0032 (2)	0.0069 (2)	−0.0006 (2)
S3	0.0290 (3)	0.0286 (3)	0.0117 (3)	−0.0060 (2)	0.0022 (2)	0.0025 (2)
S4	0.0282 (3)	0.0332 (3)	0.0131 (3)	−0.0068 (3)	0.0051 (2)	0.0014 (2)
O1	0.0294 (10)	0.0400 (11)	0.0208 (9)	−0.0022 (9)	−0.0013 (8)	−0.0006 (8)
O2	0.0246 (10)	0.0416 (12)	0.0313 (11)	−0.0046 (9)	0.0025 (8)	−0.0013 (9)
N1	0.0257 (11)	0.0236 (10)	0.0149 (10)	−0.0024 (9)	0.0041 (8)	−0.0016 (8)
N2	0.0258 (11)	0.0271 (11)	0.0163 (10)	−0.0043 (9)	0.0033 (9)	0.0012 (9)
C1	0.0234 (12)	0.0153 (11)	0.0168 (11)	0.0006 (9)	0.0036 (9)	−0.0018 (9)
C2	0.0249 (13)	0.0256 (13)	0.0201 (12)	−0.0042 (10)	0.0007 (10)	−0.0027 (10)
C3	0.0248 (13)	0.0337 (15)	0.0273 (14)	0.0014 (11)	0.0023 (11)	0.0002 (12)
C4	0.0323 (15)	0.0301 (14)	0.0208 (13)	0.0020 (12)	0.0029 (11)	0.0029 (11)
C5	0.0291 (14)	0.0320 (14)	0.0140 (11)	−0.0044 (11)	0.0040 (10)	−0.0019 (10)
C6	0.0233 (12)	0.0204 (11)	0.0160 (11)	0.0013 (9)	0.0037 (9)	−0.0002 (9)
C7	0.0293 (14)	0.0290 (13)	0.0212 (12)	−0.0091 (11)	0.0053 (11)	0.0022 (11)
C8	0.0284 (14)	0.0373 (15)	0.0278 (14)	−0.0074 (12)	0.0083 (11)	−0.0038 (12)
C9	0.0300 (14)	0.0314 (15)	0.0253 (13)	−0.0019 (12)	−0.0002 (11)	−0.0020 (11)
C10	0.0265 (13)	0.0295 (13)	0.0161 (12)	−0.0074 (11)	0.0010 (10)	−0.0027 (10)
C11	0.0279 (13)	0.0244 (13)	0.0260 (13)	0.0111 (11)	0.0074 (11)	0.0042 (10)
C12	0.0264 (13)	0.0222 (12)	0.0228 (12)	0.0052 (10)	0.0043 (10)	−0.0042 (10)

Sn—S1	2.5429 (6)	C3—H3A	0.9900
Sn—S2	2.8923 (6)	C3—H3B	0.9900
Sn—S3	2.5649 (7)	C4—C5	1.509 (4)
Sn—S4	2.9137 (6)	C4—H4A	0.9900
Sn—C11	2.132 (3)	C4—H4B	0.9900
Sn—C12	2.111 (3)	C5—H5A	0.9900
C1—S1	1.747 (3)	C5—H5B	0.9900
C1—S2	1.702 (3)	C7—C8	1.505 (4)
C6—S3	1.750 (3)	C7—H7A	0.9900
C6—S4	1.697 (3)	C7—H7B	0.9900
O1—C4	1.421 (4)	C8—H8A	0.9900
O1—C3	1.428 (4)	C8—H8B	0.9900
O2—C9	1.418 (4)	C9—C10	1.512 (4)
O2—C8	1.424 (4)	C9—H9A	0.9900
N1—C1	1.335 (3)	C9—H9B	0.9900
N1—C2	1.472 (3)	C10—H10A	0.9900
N1—C5	1.473 (3)	C10—H10B	0.9900
N2—C6	1.328 (4)	C11—H11A	0.9800
N2—C7	1.468 (3)	C11—H11B	0.9800
N2—C10	1.470 (3)	C11—H11C	0.9800
C2—C3	1.515 (4)	C12—H12A	0.9800
C2—H2A	0.9900	C12—H12B	0.9800
C2—H2B	0.9900	C12—H12C	0.9800
S1—Sn—S2	65.935 (19)	H4A—C4—H4B	108.0
S1—Sn—S3	85.878 (19)	N1—C5—C4	110.3 (2)
S1—Sn—S4	150.95 (2)	N1—C5—H5A	109.6
S1—Sn—C11	99.49 (8)	C4—C5—H5A	109.6
S1—Sn—C12	104.96 (8)	N1—C5—H5B	109.6
S2—Sn—S3	151.798 (18)	C4—C5—H5B	109.6
S2—Sn—S4	143.066 (18)	H5A—C5—H5B	108.1
S2—Sn—C11	86.87 (8)	N2—C6—S4	122.32 (19)
S2—Sn—C12	84.93 (8)	N2—C6—S3	119.1 (2)
S3—Sn—S4	65.137 (18)	S4—C6—S3	118.56 (15)
S3—Sn—C12	102.37 (8)	N2—C7—C8	109.1 (2)
S3—Sn—C11	99.28 (8)	N2—C7—H7A	109.9
S4—Sn—C11	84.20 (8)	C8—C7—H7A	109.9
S4—Sn—C12	84.15 (7)	N2—C7—H7B	109.9
C11—Sn—C12	148.24 (11)	C8—C7—H7B	109.9
C1—S1—Sn	92.73 (8)	H7A—C7—H7B	108.3
C1—S2—Sn	82.29 (9)	O2—C8—C7	111.4 (2)
C6—S3—Sn	92.55 (9)	O2—C8—H8A	109.3
C6—S4—Sn	82.27 (9)	C7—C8—H8A	109.3
C4—O1—C3	109.5 (2)	O2—C8—H8B	109.3
C9—O2—C8	110.2 (2)	C7—C8—H8B	109.3
C1—N1—C2	122.2 (2)	H8A—C8—H8B	108.0
C1—N1—C5	123.3 (2)	O2—C9—C10	111.8 (2)
C2—N1—C5	113.0 (2)	O2—C9—H9A	109.2
C6—N2—C7	124.6 (2)	C10—C9—H9A	109.2
C6—N2—C10	123.2 (2)	O2—C9—H9B	109.2
C7—N2—C10	112.2 (2)	C10—C9—H9B	109.2
N1—C1—S2	122.6 (2)	H9A—C9—H9B	107.9
N1—C1—S1	118.35 (19)	N2—C10—C9	109.3 (2)
S2—C1—S1	119.04 (14)	N2—C10—H10A	109.8
N1—C2—C3	110.0 (2)	C9—C10—H10A	109.8
N1—C2—H2A	109.7	N2—C10—H10B	109.8
C3—C2—H2A	109.7	C9—C10—H10B	109.8
N1—C2—H2B	109.7	H10A—C10—H10B	108.3
C3—C2—H2B	109.7	Sn—C11—H11A	109.5
H2A—C2—H2B	108.2	Sn—C11—H11B	109.5
O1—C3—C2	111.7 (2)	H11A—C11—H11B	109.5
O1—C3—H3A	109.3	Sn—C11—H11C	109.5
C2—C3—H3A	109.3	H11A—C11—H11C	109.5
O1—C3—H3B	109.3	H11B—C11—H11C	109.5
C2—C3—H3B	109.3	Sn—C12—H12A	109.5
H3A—C3—H3B	107.9	Sn—C12—H12B	109.5
O1—C4—C5	111.3 (2)	H12A—C12—H12B	109.5
O1—C4—H4A	109.4	Sn—C12—H12C	109.5
C5—C4—H4A	109.4	H12A—C12—H12C	109.5
O1—C4—H4B	109.4	H12B—C12—H12C	109.5
C5—C4—H4B	109.4
C2—N1—C1—S2	5.5 (4)	C7—N2—C6—S4	179.6 (2)
C5—N1—C1—S2	171.0 (2)	C10—N2—C6—S4	−3.5 (4)
C2—N1—C1—S1	−173.9 (2)	C7—N2—C6—S3	−0.7 (4)
C5—N1—C1—S1	−8.4 (3)	C10—N2—C6—S3	176.2 (2)
Sn—S2—C1—N1	179.7 (2)	Sn—S4—C6—N2	168.6 (2)
Sn—S2—C1—S1	−0.98 (13)	Sn—S4—C6—S3	−11.13 (13)
Sn—S1—C1—N1	−179.5 (2)	Sn—S3—C6—N2	−167.2 (2)
Sn—S1—C1—S2	1.11 (15)	Sn—S3—C6—S4	12.56 (15)
C1—N1—C2—C3	−143.1 (3)	C6—N2—C7—C8	122.6 (3)
C5—N1—C2—C3	50.1 (3)	C10—N2—C7—C8	−54.6 (3)
C4—O1—C3—C2	61.3 (3)	C9—O2—C8—C7	−60.3 (3)
N1—C2—C3—O1	−55.1 (3)	N2—C7—C8—O2	57.4 (3)
C3—O1—C4—C5	−61.7 (3)	C8—O2—C9—C10	59.5 (3)
C1—N1—C5—C4	142.5 (3)	C6—N2—C10—C9	−123.5 (3)
C2—N1—C5—C4	−50.8 (3)	C7—N2—C10—C9	53.7 (3)
O1—C4—C5—N1	56.3 (3)	O2—C9—C10—N2	−55.8 (3)

D—H···A	D—H	H···A	D···A	D—H···A
C10—H10A···S1i	0.99	2.86	3.809 (3)	161
C12—H12C···O1ii	0.98	2.47	3.399 (4)	158