A 1:1 adduct between di­methyl­tin dibromide and N-methyl­pyrrolidinone (NMP)

The title compound, di­bromo­di­methyl(N-methyl­pyrrolidin-2-one-O)­tin(IV), [SnBr₂(CH₃)₂(C₅H₉NO)], exhibits pentacoordination of the Sn atom, with long and short Sn-Br bonds [2.6737 (4) and 2.5256 (4) Å, respectively]. The distorted trigonal-bipyramidal coordination polyhedron has two methyl groups and one Br atom in the equatorial plane, the second Br atom and the N-methyl­pyrrolidinone (NMP) ligand occupying the apical positions.

S1. Comment

Recently, molecular complexes derived from 1:2 complexation of dimethyltin dihalides by N-methylpyrrolidinone (NMP) have been presented (König et al., 2000); these have a distorted octahedral geometry. Complexes of dimethyltin dihalides with a single ligand such as DMF, DMSO or HMPT are less well known because several such electron-donor solvents favour a 1:2 composition. The 1:1 reaction of dimethyltin dibromide with NMP leads to the formation of the title complex.

In the crystal of the title compound, the atoms bound to the Sn atom form a distorted trigonal–bipyramidal geometry. The angle between the two axial ligands NMP and Br2 is 177.50 (5)° and thus close to the ideal angle of 180°. The deviation from ideal geometry is manifested most clearly by the widened C1—Sn—C2 angle of 144.11 (11)° and by the narrowed C1—Sn—Br2 and C2—Sn—Br2 angles of 105.58 (8) and 108.98 (8)°, respectively, compared with a value of 120° for an ideal angle in the equatorial plane. This plane contains two methyl groups and one bromine and is displaced somewhat towards the axial NMP ligand. This becomes obvious from the values of the angles between the equatorial and axial ligands: (i) O1—Sn1—C1 89.35 (9)°, O1—Sn1—C2 84.94 (10)° and O1—Sn1—Br2 84.02 (5)°; (ii) Br1—Sn1—C1 92.82 (7)°, Br1—Sn1—C2 94.00 (8)° and Br1—Sn1—Br2 94.201 (12)°. This geometry has been observed for five other coordinated dimethyltin dihalide complexes (Matsubayashi et al., 1968; Liengme et al., 1972). The Sn—C bond lengths of the title compound [2.107 (3) and 2.119 (2) Å] are in the range of previously reported values of dimethyltin dihalide complexes with NMP ligands (König et al., 2000) and of other five-coordinated methyltin species (Clark et al., 1964; Schlemper & Britton, 1966; Forder & Sheldrick, 1970). The Sn—O bond length in this compound [2.3205 (17) Å] also correlates with known values (König et al., 2000). The two Sn—Br bond lengths in the title compound differ, the values being as follows: (i) Sn—Br_ax 2.6737 (4) Å; (ii) Sn—Br_eq 2.5256 (4) Å. The Sn—Br bond length in the equatorial plane is comparable with reported values of uncomplexed dimethyltin dibromide (Skinner & Sutton, 1944) and (4-bromo-1,2,3,4-tetraphenyl-cis,cis-1,3-butadienyl)dimethyltin bromide (Boer et al., 1970). The bond length between tin and the axial bromine ligand is in the range found for cis-dibromo-trans-dimethyl-cis-bis(N-methylpyrrolidinone)tin(IV) (König et al., 2000). The values of the bond lengths and bond angles in the NMP ligand are comparable with those observed in other NMP coordinated organometallic compounds (Churchill & Rotella, 1979) and in free NMP (Müller et al., 1996). The torsion angles vary from 1.3° for C12—C11—N1—C14 to 23.4° for C12—C13—C14—N1, these values in uncomplexed NMP being 4.5 and 19.8°, respectively.

S2. Experimental

The title compound was prepared by the reaction of N-methylpyrrolidinone (0.99 g, 0.96 ml, 20 mmol) with freshly sublimed dibromodimethylstannane (3.09 g, 10 mmol) derived from the reaction of dimethyltin oxide with HBr (Pfeiffer, 1902) in 10 ml of dry diethyl ether. The reaction mixture is stirred for 30 min and afterwards stored in a refrigerator at 278 K. Colourless crystals are obtained in quantitative yield after filtration and drying in vacuo, m.p. 315 K. A solution of the complex (80 mg) in C₆D₆ (410 mg) gives the following values for the structure-relevant NMR parameters: ²J(¹¹⁹Sn-¹³C-¹H) = 77 Hz, ¹J(¹¹⁹Sn-¹³C) = 561 Hz and δ(¹¹⁹Sn) = −34.8 p.p.m. These values represent an equilibrium between complexed and uncomplexed dimethyltin dibromide molecules, which is as expected shifted when the pure complex is studied at 325 K: ²J(¹¹⁹Sn-¹³C-¹H) = 83 Hz, ¹J(¹¹⁹Sn-¹³C) = 637 Hz, δ(¹¹⁹Sn) = −95.8 p.p.m.. The structure-relevant FT–IR data are as follows (neat, CsBr plates): ν (cm⁻¹) = 2982 (vw, ν_C—H), 2928 (vw, ν_C—H), 2897 (vw, ν_C—H), 1637 (versus, ν_C=O), 562 (w, ν_Sn—C), 514 (w, ν_Sn—C), 222 (s, ν_Sn—Br), 211 (m, ν_Sn—Br) (McDermott, 1986; Matsubayashi et al., 1968).

S3. Refinement

The data collections covered the whole sphere of reciprocal space. The crystal to detector distance was 3.5 cm. Crystal decay was monitored by repeating the initial frames at the end of data collection. Analysing the duplicate reflections there were no indications for any decay. The structures were solved by direct methods (Sheldrick, 1990) and successive difference Fourier syntheses. Refinement applied full-matrix least-squares methods (Sheldrick, 1997). All H atoms were placed in calculated positions and refined with a riding model (including free rotation about C—C bonds), and with U_iso constrained to be 1.5U_eq of the carrier atom.

Computing details

Data collection: Nonius KappaCCD software; cell refinement: DENZO and SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997) and PARST95 (Nardelli, 1995).

(I)

Crystal data

[SnBr2(CH3)2(C5H9NO)]	F(000) = 768
Mr = 407.71	Dx = 2.214 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71069 Å
a = 10.652 (1) Å	Cell parameters from 9229 reflections
b = 7.002 (1) Å	θ = 2.5–27.1°
c = 16.427 (1) Å	µ = 8.59 mm^−1
β = 93.36 (1)°	T = 173 K
V = 1223.1 (2) Å^3	Parallelepiped, colourless
Z = 4	0.2 × 0.2 × 0.2 mm

Data collection

Nonius KappaCCD diffractometer	2379 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.041
Graphite monochromator	θmax = 27.1°, θmin = 2.5°
Detector resolution: 10 vertical, 18 horizontal pixels mm^-1	h = −13→13
626 frames via ω rotation (Δω = 1°) at different θ values and two times 38 s per frame scans	k = −8→8
9229 measured reflections	l = −20→20
2682 independent 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)] = 0.024	H-atom parameters constrained
wR(F^2) = 0.059	Calculated w = 1/[σ^2(Fo^2) + (0.0317P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.05	(Δ/σ)max = 0.001
2682 reflections	Δρmax = 0.88 e Å^−3
113 parameters	Δρmin = −0.93 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0025 (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	0.811080 (16)	0.74951 (2)	0.185142 (10)	0.02277 (9)
Br1	0.92241 (3)	0.61543 (4)	0.323657 (17)	0.03551 (10)
Br2	0.63049 (3)	0.51577 (3)	0.184962 (15)	0.02864 (10)
C1	0.7468 (3)	0.9990 (3)	0.24263 (15)	0.0299 (6)
H1A	0.8067	1.1000	0.2375	0.045*
H1B	0.7372	0.9733	0.2993	0.045*
H1C	0.6672	1.0368	0.2171	0.045*
C2	0.9500 (3)	0.6407 (4)	0.11158 (17)	0.0353 (7)
H2A	0.9222	0.6532	0.0552	0.053*
H2B	0.9643	0.5083	0.1242	0.053*
H2C	1.0267	0.7109	0.1218	0.053*
O1	0.7131 (2)	0.8522 (3)	0.06305 (10)	0.0349 (5)
C11	0.7122 (3)	0.9969 (3)	0.01788 (14)	0.0246 (6)
C12	0.7847 (3)	1.1782 (4)	0.03235 (16)	0.0317 (6)
H12A	0.8729	1.1600	0.0228	0.048*
H12B	0.7774	1.2239	0.0876	0.048*
C13	0.7228 (3)	1.3176 (4)	−0.02993 (16)	0.0322 (6)
H13A	0.6603	1.3960	−0.0052	0.048*
H13B	0.7849	1.4000	−0.0527	0.048*
C14	0.6613 (3)	1.1865 (4)	−0.09545 (16)	0.0314 (6)
H14A	0.5811	1.2374	−0.1164	0.047*
H14B	0.7154	1.1692	−0.1403	0.047*
N1	0.6447 (2)	1.0080 (3)	−0.05207 (12)	0.0247 (5)
C15	0.5759 (3)	0.8472 (4)	−0.08914 (16)	0.0337 (6)
H15A	0.6190	0.8014	−0.1350	0.051*
H15B	0.4927	0.8876	−0.1071	0.051*
H15C	0.5705	0.7467	−0.0498	0.051*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Sn1	0.02696 (14)	0.01880 (12)	0.02245 (13)	0.00207 (6)	0.00053 (9)	0.00061 (6)
Br1	0.03496 (19)	0.03579 (17)	0.03442 (17)	−0.00065 (12)	−0.00950 (13)	0.00971 (11)
Br2	0.03064 (18)	0.02591 (15)	0.02893 (16)	−0.00345 (10)	−0.00191 (12)	0.00106 (10)
C1	0.0378 (17)	0.0252 (12)	0.0266 (14)	0.0062 (11)	0.0017 (12)	−0.0024 (10)
C2	0.0341 (17)	0.0335 (15)	0.0394 (16)	0.0022 (12)	0.0103 (13)	−0.0070 (12)
O1	0.0518 (13)	0.0280 (10)	0.0240 (10)	0.0012 (9)	−0.0051 (9)	0.0071 (7)
C11	0.0283 (15)	0.0276 (13)	0.0180 (12)	0.0068 (10)	0.0012 (11)	−0.0004 (10)
C12	0.0368 (16)	0.0303 (13)	0.0276 (14)	−0.0014 (12)	−0.0031 (12)	0.0003 (11)
C13	0.0438 (18)	0.0246 (13)	0.0286 (14)	0.0010 (12)	0.0065 (13)	0.0013 (11)
C14	0.0397 (17)	0.0271 (13)	0.0271 (14)	0.0057 (12)	0.0006 (13)	0.0052 (11)
N1	0.0303 (13)	0.0241 (10)	0.0194 (10)	0.0030 (9)	−0.0012 (9)	0.0021 (8)
C15	0.0373 (17)	0.0337 (14)	0.0299 (14)	−0.0029 (12)	0.0009 (13)	−0.0022 (11)

Geometric parameters (Å, º)

Sn1—C2	2.107 (3)	C12—C13	1.535 (4)
Sn1—C1	2.119 (2)	C12—H12A	0.9700
Sn1—O1	2.3205 (17)	C12—H12B	0.9700
Sn1—Br2	2.5256 (4)	C13—C14	1.532 (4)
Sn1—Br1	2.6737 (4)	C13—H13A	0.9700
C1—H1A	0.9600	C13—H13B	0.9700
C1—H1B	0.9600	C14—N1	1.454 (3)
C1—H1C	0.9600	C14—H14A	0.9700
C2—H2A	0.9600	C14—H14B	0.9700
C2—H2B	0.9600	N1—C15	1.458 (3)
C2—H2C	0.9600	C15—H15A	0.9600
O1—C11	1.256 (3)	C15—H15B	0.9600
C11—N1	1.321 (3)	C15—H15C	0.9600
C11—C12	1.498 (4)
C2—Sn1—C1	144.11 (11)	C11—C12—H12A	111.0
C2—Sn1—O1	84.94 (10)	C13—C12—H12A	111.0
C1—Sn1—O1	89.35 (9)	C11—C12—H12B	111.0
C2—Sn1—Br2	108.98 (8)	C13—C12—H12B	111.0
C1—Sn1—Br2	105.58 (8)	H12A—C12—H12B	109.0
O1—Sn1—Br2	84.02 (5)	C14—C13—C12	103.7 (2)
C2—Sn1—Br1	94.00 (8)	C14—C13—H13A	111.0
C1—Sn1—Br1	92.82 (7)	C12—C13—H13A	111.0
O1—Sn1—Br1	177.50 (5)	C14—C13—H13B	111.0
Br2—Sn1—Br1	94.201 (12)	C12—C13—H13B	111.0
Sn1—C1—H1A	109.5	H13A—C13—H13B	109.0
Sn1—C1—H1B	109.5	N1—C14—C13	103.3 (2)
H1A—C1—H1B	109.5	N1—C14—H14A	111.1
Sn1—C1—H1C	109.5	C13—C14—H14A	111.1
H1A—C1—H1C	109.5	N1—C14—H14B	111.1
H1B—C1—H1C	109.5	C13—C14—H14B	111.1
Sn1—C2—H2A	109.5	H14A—C14—H14B	109.1
Sn1—C2—H2B	109.5	C11—N1—C14	113.7 (2)
H2A—C2—H2B	109.5	C11—N1—C15	123.5 (2)
Sn1—C2—H2C	109.5	C14—N1—C15	122.1 (2)
H2A—C2—H2C	109.5	N1—C15—H15A	109.5
H2B—C2—H2C	109.5	N1—C15—H15B	109.5
C11—O1—Sn1	138.44 (17)	H15A—C15—H15B	109.5
O1—C11—N1	123.1 (2)	N1—C15—H15C	109.5
O1—C11—C12	127.2 (2)	H15A—C15—H15C	109.5
N1—C11—C12	109.7 (2)	H15B—C15—H15C	109.5
C11—C12—C13	103.6 (2)
C2—Sn1—O1—C11	−90.0 (3)	C11—C12—C13—C14	−22.8 (3)
C1—Sn1—O1—C11	54.5 (3)	C12—C13—C14—N1	23.4 (3)
Br2—Sn1—O1—C11	160.3 (3)	O1—C11—N1—C14	−178.1 (2)
Br1—Sn1—O1—C11	−155.2 (10)	C12—C11—N1—C14	1.3 (3)
Sn1—O1—C11—N1	178.07 (18)	O1—C11—N1—C15	−7.5 (4)
Sn1—O1—C11—C12	−1.3 (4)	C12—C11—N1—C15	172.0 (2)
O1—C11—C12—C13	−166.4 (3)	C13—C14—N1—C11	−16.2 (3)
N1—C11—C12—C13	14.1 (3)	C13—C14—N1—C15	173.0 (2)