The chloro­(diethyl­amino)­di­methyl­tin dimer

The title compound, di-[mu]-diethyl­amido-N:N-bis­[chloro­di­methyl­tin(IV)], consists of discrete [Sn₂Cl₂(CH₃)₄(C₄H₁₀N)₂] dimer mol­ecules, with Sn atoms linked by bridging diethyl­amido groups. The coordination geometry about the metal atom is distorted trigonal bipyramidal, with the two methyl C atoms and one N atom in the equatorial plane, and the Cl and second N atom in axial positions.

S1. Comment

In the course of our studies on diethylaminodimethylstannane(IV), [(CH₃)₂Sn{N(C₂H₅)₂}], as a novel molecular precursor for the Chemical Vapour Deposition (CVD) of SnO₂ thin films (Barreca et al., 1999), we have observed that defects of LiN(C₂H₅)₂ in the synthesis of

(CH₃)₂SnCl₂ + 2LiN(C₂H₅)₂ → (CH₃)₂Sn(N(C₂H₅)₂)₂ + 2LiCl_(s)

induce the formation of diethylaminodimethyltin chloride, (CH₃)₂Sn(N(C₂H₅)₂)Cl, in accordance with literature data (Davies & Kennedy, 1970, and reference therein). In this work, the latter compound was reported to be unstable, so its complete characterization was not performed. Nevertheless, two different dimeric structures were proposed for it. In order to clarify the question, we have decided to verify the possibility of obtaining (CH₃)₂Sn(N(C₂H₅)₂)Cl by the 1:1 reaction of (CH₃)₂SnCl₂ and LiN(C₂H₅)₂:

(CH₃)₂SnCl₂ + LiN(C₂H₅)₂ → (CH₃)₂Sn(N(C₂H₅)₂)Cl + LiCl_(s)

and to undertake a structure determination of the obtained product. Operating under controlled atmosphere conditions, we obtained suitable crystals for X-ray diffraction of the title compound, (I). The structure consists of discrete dimers with an approximate binary symmetry. Two Sn atoms are bridged by two diethylamino N atoms, forming an irregular square. The coordination geometry about the Sn atom is distorted trigonal bipyramidal, with the two methyl C atoms and one N atom in the equatorial plane, and the Cl and second N atom in axial positions. The Sn—N bond distances are different, the shorter ones are for the equatorial positions [Sn1—N1_eq 2.125 (8) and Sn2—N2_eq 2.136 (7) Å], while the longer ones are for the axial positions [Sn1—N2_ax 2.419 (7) and Sn2—N1_ax 2.444 (7) Å]. The latter distances are comparable to the values of 2.459 (15) and 2.453 (14) Å found for the axial Sn—N bond distances in the dimeric structure of [(CH₃)₂Cl(N₂C₃H₃)Sn(CH₂)Sn(N₂C₃H₃)Cl(CH₃)₂] with trigonal bipyramidal coordination geometry (Austin et al., 1987). The Sn—C(methyl) bond distances present the usual values found in similar derivatives (Chivers et al., 1989). The two axial Sn—Cl bond distances of 2.525 (2) and 2.543 (3) Å are comparable with the averaged value of 2.54 (2) Å reported for the two axial bonds in the Sn(CH₃)₂Cl₃⁻ anion (Einstein & Penfold, 1968).

S2. Experimental

The reaction between (CH₃)₂SnCl₂ (3.5 g, 16 mmol) and LiN(C₂H₅)₂ (1.25 g, 16 mmol) in a 1:1 molar ratio was carried out in n-hexane (Davies & Kennedy, 1970, and references therein). The suspension was stirred overnight. The LiCl was separated by filtration and the n-hexane solution was concentrated under vacuum,giving a colourless crystalline product suitable for a single-crystal X-ray analysis. ¹H NMR signals (Brüker BHZ 200/52) spectrometer; positive δ values (p.p.m.) downfield from internal Si(CH₃)₄, in C₆D₆): 2.95 (quartet, 4H, NCH₂CH₃), 1.04 (triplet, 6H, NCH₂CH₃), 0.31 (singlet, 6H, SnCH₃).

S3. Refinement

The H atoms of the C atoms were introduced at calculated positions in their described geometries and during refinement were allowed to ride on the attached C atom with fixed isotropic displacement parameters (1.2U_eq of the parent C atom).

Computing details

Data collection: FEBO (Belletti, 1993); cell refinement: FEBO; data reduction: FEBO; program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); software used to prepare material for publication: PARST94 (Nardelli, 1995).

Di-µ-diethylamido-N:N-bis[chlorodimethyltin(IV)]

Crystal data

[Sn2Cl2(CH3)4(C4H10N)2]	F(000) = 2016
Mr = 512.68	Dx = 1.718 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 16.015 (3) Å	Cell parameters from 30 reflections
b = 10.219 (3) Å	θ = 10–14°
c = 24.275 (5) Å	µ = 2.78 mm^−1
β = 93.94 (3)°	T = 293 K
V = 3963.4 (16) Å^3	Prism, white
Z = 8	0.50 × 0.40 × 0.24 mm

Data collection

Philips PW1100 four-circle diffractometer	3144 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.031
Graphite monochromator	θmax = 25.0°, θmin = 3.4°
Profile fitted θ/2θ scans (Lehman & Larsen 1974)	h = −19→18
Absorption correction: ψ scan (North et al., 1968)	k = 0→12
Tmin = 0.276, Tmax = 0.513	l = 0→28
4818 measured reflections	3 standard reflections every 200 min
3183 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.056	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.140	H-atom parameters constrained
S = 1.21	Calculated w = 1/[σ^2(Fo^2) + (0.0514P)^2 + 78.9387P] where P = (Fo^2 + 2Fc^2)/3
3114 reflections	(Δ/σ)max = 0.003
171 parameters	Δρmax = 1.03 e Å^−3
no restraints restraints	Δρmin = −1.27 e Å^−3

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.

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

	x	y	z	Uiso*/Ueq
Sn1	0.19674 (4)	0.18519 (6)	0.15376 (2)	0.0427 (2)
Sn2	0.17511 (3)	−0.07882 (6)	0.06777 (2)	0.0347 (2)
Cl1	0.3066 (2)	0.3624 (3)	0.17224 (14)	0.0782 (9)
Cl2	0.05418 (16)	−0.2062 (3)	0.02211 (11)	0.0575 (7)
N1	0.2811 (4)	0.0509 (7)	0.1204 (3)	0.0380 (16)
N2	0.1057 (4)	0.0008 (7)	0.1319 (3)	0.0344 (15)
C1	0.1782 (11)	0.1775 (14)	0.2391 (5)	0.085 (4)
H1A	0.1996	0.0962	0.2541	0.102*
H1B	0.1195	0.1836	0.2444	0.102*
H1C	0.2071	0.2490	0.2576	0.102*
C2	0.1344 (8)	0.3112 (11)	0.0957 (5)	0.067 (3)
H2A	0.1747	0.3652	0.0790	0.080*
H2B	0.0960	0.3655	0.1140	0.080*
H2C	0.1043	0.2601	0.0677	0.080*
C3	0.2420 (7)	−0.2544 (10)	0.0820 (5)	0.058 (3)
H3A	0.2130	−0.3247	0.0626	0.070*
H3B	0.2466	−0.2731	0.1208	0.070*
H3C	0.2970	−0.2456	0.0689	0.070*
C4	0.1720 (6)	0.0495 (11)	−0.0012 (4)	0.053 (2)
H4A	0.1149	0.0659	−0.0141	0.063*
H4B	0.2010	0.0099	−0.0303	0.063*
H4C	0.1987	0.1306	0.0094	0.063*
C5	0.3424 (6)	0.1160 (11)	0.0852 (4)	0.054 (3)
H5A	0.3811	0.1673	0.1089	0.064*
H5B	0.3121	0.1759	0.0601	0.064*
C6	0.3924 (7)	0.0219 (14)	0.0515 (6)	0.074 (4)
H6A	0.4296	0.0708	0.0300	0.089*
H6B	0.3548	−0.0284	0.0274	0.089*
H6C	0.4244	−0.0359	0.0760	0.089*
C7	0.3256 (6)	−0.0293 (10)	0.1632 (4)	0.052 (2)
H7A	0.3534	−0.0997	0.1448	0.062*
H7B	0.2840	−0.0692	0.1851	0.062*
C8	0.3903 (9)	0.0370 (16)	0.2027 (6)	0.093 (5)
H8A	0.3640	0.1058	0.2222	0.111*
H8B	0.4340	0.0732	0.1822	0.111*
H8C	0.4138	−0.0261	0.2287	0.111*
C9	0.1019 (6)	−0.0890 (10)	0.1808 (4)	0.050 (2)
H9A	0.0758	−0.0420	0.2098	0.060*
H9B	0.1588	−0.1091	0.1945	0.060*
C10	0.0553 (8)	−0.2173 (12)	0.1709 (5)	0.065 (3)
H10A	0.0599	−0.2690	0.2040	0.078*
H10B	0.0792	−0.2644	0.1416	0.078*
H10C	−0.0026	−0.1997	0.1608	0.078*
C11	0.0191 (6)	0.0386 (11)	0.1103 (4)	0.050 (2)
H11A	−0.0131	−0.0401	0.1021	0.060*
H11B	0.0225	0.0869	0.0762	0.060*
C12	−0.0266 (7)	0.1221 (14)	0.1509 (6)	0.074 (4)
H12A	−0.0773	0.1557	0.1328	0.089*
H12B	0.0086	0.1936	0.1635	0.089*
H12C	−0.0399	0.0694	0.1819	0.089*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Sn1	0.0514 (4)	0.0504 (4)	0.0263 (3)	−0.0068 (3)	0.0025 (3)	−0.0030 (3)
Sn2	0.0330 (3)	0.0479 (4)	0.0229 (3)	−0.0005 (2)	−0.0008 (2)	−0.0004 (2)
Cl1	0.087 (2)	0.0688 (19)	0.078 (2)	−0.0299 (17)	−0.0017 (17)	−0.0160 (16)
Cl2	0.0513 (14)	0.0705 (17)	0.0481 (14)	−0.0111 (12)	−0.0152 (11)	−0.0090 (12)
N1	0.031 (3)	0.050 (4)	0.032 (4)	−0.007 (3)	−0.006 (3)	−0.001 (3)
N2	0.032 (3)	0.053 (4)	0.019 (3)	−0.004 (3)	0.000 (3)	0.007 (3)
C1	0.136 (13)	0.085 (9)	0.034 (6)	−0.030 (9)	0.018 (7)	−0.013 (6)
C2	0.075 (8)	0.056 (7)	0.068 (8)	−0.003 (6)	−0.005 (6)	0.015 (6)
C3	0.055 (6)	0.048 (6)	0.071 (7)	0.010 (5)	−0.009 (5)	−0.001 (5)
C4	0.052 (6)	0.073 (7)	0.032 (5)	0.002 (5)	0.000 (4)	0.007 (5)
C5	0.036 (5)	0.067 (7)	0.058 (6)	−0.018 (5)	0.000 (4)	0.003 (5)
C6	0.052 (6)	0.093 (9)	0.080 (9)	−0.005 (6)	0.028 (6)	0.004 (7)
C7	0.045 (5)	0.057 (6)	0.050 (6)	−0.010 (5)	−0.020 (4)	0.019 (5)
C8	0.083 (9)	0.108 (11)	0.079 (9)	−0.017 (8)	−0.055 (8)	0.013 (8)
C9	0.049 (5)	0.072 (7)	0.028 (5)	−0.011 (5)	0.000 (4)	0.012 (4)
C10	0.072 (7)	0.073 (7)	0.049 (6)	−0.025 (6)	−0.002 (5)	0.013 (6)
C11	0.035 (5)	0.074 (7)	0.041 (5)	0.010 (5)	0.003 (4)	−0.001 (5)
C12	0.044 (6)	0.094 (9)	0.085 (9)	0.002 (6)	0.021 (6)	−0.016 (8)

Geometric parameters (Å, º)

Sn1—C2	2.109 (11)	C4—H4C	0.9600
Sn1—C1	2.115 (11)	C5—C6	1.525 (16)
Sn1—N1	2.125 (8)	C5—H5A	0.9700
Sn1—N2	2.419 (7)	C5—H5B	0.9700
Sn1—Cl1	2.543 (3)	C6—H6A	0.9600
Sn2—C3	2.106 (10)	C6—H6B	0.9600
Sn2—C4	2.125 (10)	C6—H6C	0.9600
Sn2—N2	2.136 (7)	C7—C8	1.523 (14)
Sn2—N1	2.444 (7)	C7—H7A	0.9700
Sn2—Cl2	2.525 (2)	C7—H7B	0.9700
N1—C7	1.468 (11)	C8—H8A	0.9600
N1—C5	1.500 (12)	C8—H8B	0.9600
N2—C11	1.499 (11)	C8—H8C	0.9600
N2—C9	1.504 (11)	C9—C10	1.519 (14)
C1—H1A	0.9600	C9—H9A	0.9700
C1—H1B	0.9600	C9—H9B	0.9700
C1—H1C	0.9600	C10—H10A	0.9600
C2—H2A	0.9600	C10—H10B	0.9600
C2—H2B	0.9600	C10—H10C	0.9600
C2—H2C	0.9600	C11—C12	1.527 (15)
C3—H3A	0.9600	C11—H11A	0.9700
C3—H3B	0.9600	C11—H11B	0.9700
C3—H3C	0.9600	C12—H12A	0.9600
C4—H4A	0.9600	C12—H12B	0.9600
C4—H4B	0.9600	C12—H12C	0.9600
C2—Sn1—C1	125.9 (6)	H4A—C4—H4B	109.5
C2—Sn1—N1	115.1 (4)	Sn2—C4—H4C	109.5
C1—Sn1—N1	119.0 (5)	H4A—C4—H4C	109.5
C2—Sn1—N2	94.5 (4)	H4B—C4—H4C	109.5
C1—Sn1—N2	93.6 (4)	N1—C5—C6	114.5 (9)
N1—Sn1—N2	78.6 (2)	N1—C5—H5A	108.6
C2—Sn1—Cl1	88.4 (3)	C6—C5—H5A	108.6
C1—Sn1—Cl1	89.8 (4)	N1—C5—H5B	108.6
N1—Sn1—Cl1	94.4 (2)	C6—C5—H5B	108.6
N2—Sn1—Cl1	173.06 (19)	H5A—C5—H5B	107.6
C3—Sn2—C4	129.7 (5)	C5—C6—H6A	109.5
C3—Sn2—N2	119.3 (4)	C5—C6—H6B	109.5
C4—Sn2—N2	110.8 (4)	H6A—C6—H6B	109.5
C3—Sn2—N1	92.8 (3)	C5—C6—H6C	109.5
C4—Sn2—N1	93.2 (3)	H6A—C6—H6C	109.5
N2—Sn2—N1	77.9 (3)	H6B—C6—H6C	109.5
C3—Sn2—Cl2	89.9 (3)	N1—C7—C8	118.2 (9)
C4—Sn2—Cl2	89.8 (3)	N1—C7—H7A	107.7
N2—Sn2—Cl2	95.42 (19)	C8—C7—H7A	107.7
N1—Sn2—Cl2	173.25 (18)	N1—C7—H7B	107.7
C7—N1—C5	110.2 (7)	C8—C7—H7B	107.7
C7—N1—Sn1	112.4 (6)	H7A—C7—H7B	107.1
C5—N1—Sn1	112.9 (6)	C7—C8—H8A	109.5
C7—N1—Sn2	110.7 (5)	C7—C8—H8B	109.5
C5—N1—Sn2	113.6 (5)	H8A—C8—H8B	109.5
Sn1—N1—Sn2	96.5 (3)	C7—C8—H8C	109.5
C11—N2—C9	110.3 (7)	H8A—C8—H8C	109.5
C11—N2—Sn2	111.0 (5)	H8B—C8—H8C	109.5
C9—N2—Sn2	113.2 (6)	N2—C9—C10	116.6 (8)
C11—N2—Sn1	113.9 (6)	N2—C9—H9A	108.1
C9—N2—Sn1	111.0 (5)	C10—C9—H9A	108.1
Sn2—N2—Sn1	96.9 (2)	N2—C9—H9B	108.1
Sn1—C1—H1A	109.5	C10—C9—H9B	108.1
Sn1—C1—H1B	109.5	H9A—C9—H9B	107.3
H1A—C1—H1B	109.5	C9—C10—H10A	109.5
Sn1—C1—H1C	109.5	C9—C10—H10B	109.5
H1A—C1—H1C	109.5	H10A—C10—H10B	109.5
H1B—C1—H1C	109.5	C9—C10—H10C	109.5
Sn1—C2—H2A	109.5	H10A—C10—H10C	109.5
Sn1—C2—H2B	109.5	H10B—C10—H10C	109.5
H2A—C2—H2B	109.5	N2—C11—C12	113.0 (8)
Sn1—C2—H2C	109.5	N2—C11—H11A	109.0
H2A—C2—H2C	109.5	C12—C11—H11A	109.0
H2B—C2—H2C	109.5	N2—C11—H11B	109.0
Sn2—C3—H3A	109.5	C12—C11—H11B	109.0
Sn2—C3—H3B	109.5	H11A—C11—H11B	107.8
H3A—C3—H3B	109.5	C11—C12—H12A	109.5
Sn2—C3—H3C	109.5	C11—C12—H12B	109.5
H3A—C3—H3C	109.5	H12A—C12—H12B	109.5
H3B—C3—H3C	109.5	C11—C12—H12C	109.5
Sn2—C4—H4A	109.5	H12A—C12—H12C	109.5
Sn2—C4—H4B	109.5	H12B—C12—H12C	109.5