Dimethyl- and diethyl­dithio­cyanato­tin(IV)

The structures of dimethyl­dithio­cyanato­tin(IV), [Sn(CH₃)₂(NCS)₂], and diethyl­dithio­cyanato­tin(IV), [Sn(C₂H₅)₂(NCS)₂], have been determined. The dimethyl derivative has 2mm crystallographic symmetry and the diethyl derivative has twofold crystallographic symmetry. The experimental differences in the distances and angles around the Sn atom between the two structures agree reasonably well with the differences expected from the reaction path mapped previously [Britton & Dunitz (1981). J. Am. Chem. Soc. 103, 2971-2979].

S1. Comment

The path of the reaction R₂SnX₂ + 2Y → R₂SnY₂ + 2X was mapped (Britton & Dunitz, 1981; hereafter B&D) using the structure correlation method (Bürgi, 1975; Dunitz, 1975). A variety of R groups and X and Y atoms were used in this mapping, which showed rough but reasonable agreement for a variety of R₂SnX₂Y₂ intermediates. One of the compounds used in this study was (CH₃)₂Sn(NCS)₂ (Forder & Sheldrick, 1970; Chow, 1970). The availability of the corresponding diethyl compound suggested examining how the mapping changed with very small chemical differences.

In the structure of (CH₃)₂Sn(NCS)₂, Sn···S interactions from adjacent molecules form partial bonds and lead to the weakening of the Sn—N bonds. A redetermination of this structure, (I), is reported here, along with the structure of (C₂H₅)₂Sn(NCS)₂, (II). The replacement of CH₃ groups by C₂H₅ groups must lead to a different overall packing arrangement, and the question of interest is the extent to which any changes in the Sn—N and Sn···S distances, and the C—Sn—C, C—Sn—X and C—Sn···S angles, are consistent with each other and with the structure correlation model.

Fig. 1 shows the atom labelling and displacement ellipsoids for (I), along with a second molecule of (I) to make clear the Sn···S interactions. Fig. 2 shows the same for (II). The bond lengths and angles will be described below with one exception. In the B&D study it appeared that the Sn—C distances did not vary significantly from the Sn—C bond length of 2.10 Å given by Pauling (1960). In the present work, the Sn—C distance in (I) [2.099 (2) Å] is significantly smaller that that in (II) [2.126 (2) Å]. This discrepancy suggests that the original approach needs to be fine-tuned, but this difference has been ignored in the rest of the discussion.

The bond distances and bond angles are given in Tables 1 and 2. The Sn—N distance increases by 0.022</span><span style=" font-weight:600;">(2) Å from (I) to (II). The B&D model would predict that the Sn···S distance should decrease, the C– Sn—C angle should increase, the C—Sn—N angle should decrease and the C—Sn···S angle should increase. All of these qualitative changes are correct.

Using Pauling's (1947) bond length–bond order relationship [d(n) − d(1) = clogn], with c = 1.20 as used previously (B&D), the bond orders, n, are those given in Table 1. They do not add to 1.000 owing to the approximate nature of the model. The sums of the n values could be brought closer to 1.000 by adjusting c slightly, but this does not seem justified.

In Table 2, the experimental C—Sn—C, C—Sn—N and C—Sn···S values are compared with the values predicted from the model of B&D. There are two sets of predicted values depending on whether the C—N or C···S bond orders are used; in a perfect model these would be the same. The predicted values are in reasonable agreement with the experimental values, being within about 2°; the changes in going from (I) to (II) are within about 0.5° in all three cases.

S2. Experimental

See Chow (1970) for the synthesis of (I). The synthesis of (II) was similar, with diethyltin chloride replacing dimethyltin chloride as the starting material.

S3. Refinement

The solution and refinement were straightforward. As a test of the data, the H-atom positions and isotropic displacement parameters were refined and reasonable values were ontained even in the presence of the Sn atom.

Computing details

For both compounds, data collection: SMART (Bruker, 2002); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 1997); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures

Fig. 1. (CH3)2Sn(NCS)2. The crystallographically independent atoms are labelled as well as those additional atoms referred to in Tables 1 and 2. The molecule has 2mm symmetry, with the twofold axis along [1/4, 1/4, z]. Displacement ellipsoids are shown at the 50% probability level. The H-atom Uiso values were refined, but they are shown with arbitrary radii. The Sn···S interactions are shown with dashed bonds. [Symmetry codes: (A) 1/2 − x, 1/2 − y, z; (B) x, y, 1 + z; (C) 1/2 − x, 1/2 − y, 1 + z.]

Fig. 2. (C2H5)2Sn(NCS)2. The molecule has 2 symmetry, with the twofold axis along [0, y, 3/4]. All conventions as in Fig. 1. [Symmetry codes: (A) −x, y, 3/2 − z; (B) −x, 1 + y, 3/2 − z; (C) x, 1 + y, z.

(I) dimethyldithiocyanatotin(IV)

Crystal data

[Sn(CH3)2(NCS)2]	Dx = 2.106 Mg m^−3
Mr = 264.92	Melting point = 457–461 K
Orthorhombic, Pmmn	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ab 2a	Cell parameters from 3997 reflections
a = 9.654 (2) Å	θ = 2.6–27.5°
b = 7.769 (2) Å	µ = 3.48 mm^−1
c = 5.5692 (14) Å	T = 174 K
V = 417.70 (17) Å^3	Needle, colorless
Z = 2	0.50 × 0.10 × 0.10 mm
F(000) = 252

Data collection

Siemens SMART area-detector diffractometer	543 independent reflections
Radiation source: fine-focus sealed tube	523 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.018
ω scans	θmax = 27.5°, θmin = 3.4°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996; Blessing, 1995)	h = −12→12
Tmin = 0.50, Tmax = 0.71	k = −9→10
4698 measured reflections	l = −7→7

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)] = 0.009	All H-atom parameters refined
wR(F^2) = 0.022	w = 1/[σ^2(Fo^2) + (0.011P)^2 + 0.108P] where P = (Fo^2 + 2Fc^2)/3
S = 1.11	(Δ/σ)max = 0.001
543 reflections	Δρmax = 0.23 e Å^−3
37 parameters	Δρmin = −0.19 e Å^−3
0 restraints	Extinction correction: SHELXTL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.018 (3)

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

	x	y	z	Uiso*/Ueq
Sn1	0.2500	0.2500	0.55294 (3)	0.02054 (7)
S1	0.53344 (4)	0.2500	−0.16813 (7)	0.02979 (11)
N1	0.40056 (16)	0.2500	0.2735 (3)	0.0298 (3)
C1	0.45554 (16)	0.2500	0.0885 (3)	0.0215 (3)
C2	0.2500	−0.0094 (2)	0.6582 (3)	0.0284 (3)
H2B	0.2500	−0.021 (3)	0.826 (5)	0.054 (7)*
H2A	0.332 (2)	−0.057 (3)	0.604 (3)	0.058 (5)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Sn1	0.02847 (10)	0.01875 (9)	0.01438 (9)	0.000	0.000	0.000
S1	0.0272 (2)	0.0444 (2)	0.0178 (2)	0.000	0.00493 (15)	0.000
N1	0.0347 (7)	0.0347 (8)	0.0200 (7)	0.000	0.0043 (6)	0.000
C1	0.0232 (7)	0.0219 (7)	0.0195 (7)	0.000	−0.0031 (6)	0.000
C2	0.0322 (9)	0.0213 (8)	0.0317 (9)	0.000	0.000	0.0051 (7)

Geometric parameters (Å, º)

Sn1—C2	2.0986 (17)	S1—C1	1.6149 (16)
Sn1—C2^i	2.0986 (17)	N1—C1	1.159 (2)
Sn1—N1^i	2.1296 (15)	C2—H2B	0.94 (3)
Sn1—N1	2.1296 (15)	C2—H2A	0.925 (19)
C2—Sn1—C2^i	147.57 (11)	C1—N1—Sn1	164.22 (13)
C2—Sn1—N1^i	101.78 (4)	N1—C1—S1	179.51 (15)
C2^i—Sn1—N1^i	101.78 (4)	Sn1—C2—H2B	111.6 (16)
C2—Sn1—N1	101.78 (4)	Sn1—C2—H2A	107.3 (12)
C2^i—Sn1—N1	101.78 (4)	H2B—C2—H2A	106.5 (13)
N1^i—Sn1—N1	86.08 (8)

Symmetry code: (i) −x+1/2, −y+1/2, z.

(II) Diethyltindithiocyanatotin(IV)

Crystal data

[Sn(C2H5)2(NCS)2]	Dx = 1.916 Mg m^−3
Mr = 292.97	Melting point: 467-470 with decomposition K
Orthorhombic, Pbcn	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2n 2ab	Cell parameters from 2765 reflections
a = 14.449 (4) Å	θ = 3.2–27.4°
b = 5.5526 (14) Å	µ = 2.88 mm^−1
c = 12.660 (3) Å	T = 174 K
V = 1015.7 (5) Å^3	Plate, colorless
Z = 4	0.35 × 0.25 × 0.05 mm
F(000) = 568

Data collection

Siemens area detector diffractometer	1166 independent reflections
Radiation source: fine-focus sealed tube	1137 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.021
ω scans	θmax = 27.5°, θmin = 2.8°
Absorption correction: multi-scan SADABS; Sheldrick, 1996; Blessing, 1995	h = −18→18
Tmin = 0.40, Tmax = 0.87	k = −7→7
10750 measured reflections	l = −16→16

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)] = 0.014	All H-atom parameters refined
wR(F^2) = 0.033	w = 1/[σ^2(Fo^2) + (0.013P)^2 + 0.49P] where P = (Fo^2 + 2Fc^2)/3
S = 1.16	(Δ/σ)max = 0.001
1166 reflections	Δρmax = 0.39 e Å^−3
73 parameters	Δρmin = −0.24 e Å^−3
0 restraints	Extinction correction: SHELXTL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0014 (2)

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

	x	y	z	Uiso*/Ueq
Sn1	0.0000	0.13925 (2)	0.7500	0.01958 (7)
S1	0.15673 (3)	−0.59587 (7)	0.63634 (3)	0.02864 (10)
C1	0.11223 (10)	−0.3358 (3)	0.66391 (11)	0.0211 (3)
N1	0.08028 (10)	−0.1498 (2)	0.68338 (12)	0.0307 (3)
C3	0.16130 (13)	0.0669 (4)	0.90144 (16)	0.0400 (4)
H3A	0.1938 (15)	0.115 (4)	0.9589 (18)	0.046 (6)*
H3B	0.2031 (15)	0.075 (4)	0.8438 (18)	0.048 (6)*
H3C	0.1440 (16)	−0.106 (4)	0.9073 (18)	0.051 (6)*
C2	0.07781 (11)	0.2285 (3)	0.88700 (12)	0.0286 (3)
H2B	0.0950 (15)	0.385 (4)	0.8771 (17)	0.041 (6)*
H2A	0.0331 (16)	0.211 (4)	0.9432 (17)	0.046 (6)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Sn1	0.02204 (9)	0.01699 (9)	0.01971 (9)	0.000	−0.00309 (5)	0.000
S1	0.02773 (19)	0.02036 (17)	0.0378 (2)	0.00317 (15)	0.01069 (16)	−0.00055 (15)
C1	0.0205 (7)	0.0228 (7)	0.0201 (6)	−0.0036 (5)	0.0024 (5)	0.0011 (5)
N1	0.0326 (7)	0.0229 (7)	0.0367 (8)	0.0019 (5)	0.0056 (6)	−0.0023 (5)
C3	0.0316 (9)	0.0558 (12)	0.0327 (9)	0.0056 (9)	−0.0113 (8)	0.0022 (9)
C2	0.0279 (8)	0.0371 (9)	0.0209 (7)	−0.0013 (7)	−0.0051 (6)	−0.0035 (6)

Geometric parameters (Å, º)

Sn1—C2	2.1255 (15)	C3—C2	1.514 (3)
Sn1—C2^i	2.1255 (15)	C3—H3A	0.91 (2)
Sn1—N1^i	2.1523 (14)	C3—H3B	0.95 (2)
Sn1—N1	2.1523 (14)	C3—H3C	0.99 (2)
S1—C1	1.6189 (15)	C2—H2B	0.91 (2)
C1—N1	1.1577 (19)	C2—H2A	0.97 (2)
C2—Sn1—C2^i	153.04 (10)	H3A—C3—H3B	105.9 (18)
C2—Sn1—N1^i	98.00 (7)	C2—C3—H3C	112.3 (14)
C2^i—Sn1—N1^i	102.04 (6)	H3A—C3—H3C	110.6 (19)
C2—Sn1—N1	102.04 (6)	H3B—C3—H3C	105.1 (19)
C2^i—Sn1—N1	97.99 (7)	C3—C2—Sn1	112.44 (12)
N1^i—Sn1—N1	83.57 (8)	C3—C2—H2B	111.4 (14)
N1—C1—S1	179.82 (17)	Sn1—C2—H2B	104.7 (13)
C1—N1—Sn1	164.46 (13)	C3—C2—H2A	112.7 (13)
C2—C3—H3A	109.7 (13)	Sn1—C2—H2A	103.0 (13)
C2—C3—H3B	112.8 (13)	H2B—C2—H2A	112 (2)

Symmetry code: (i) −x, y, −z+3/2.