Substitutional disorder in a hypervalent diorganotin(IV) dihalide

Adina Rotar; Richard A Varga; Cristian Silvestru

doi:10.1107/S1600536807063386

. 2007 Dec 6;64(Pt 1):m45. doi: 10.1107/S1600536807063386

Substitutional disorder in a hypervalent diorganotin(IV) dihalide

Adina Rotar ^a, Richard A Varga ^a,^*, Cristian Silvestru ^a

PMCID: PMC2947775 PMID: 21200616

Abstract

The structure of bromidochloridobis[2-(dimethylaminomethyl)phenyl]tin(IV), [SnBr_0.65Cl_1.35(C₉H₁₂N)₂], contains two 2-(Me₂NCH₂)C₆H₄ units bonded to a Sn atom which lies on a twofold axis. The compound exhibits substitutional disorder of the halide atoms bonded to the Sn, with 1.35 occupancy for Cl and 0.65 for Br; it is isomorphous with the corresponding dichloride. The Sn atom is hexacoordinated with a (C,N)₂SnX ₂ (X = Cl/Br) distorted octahedral core as a result of the strong intramolecular N→Sn coordination trans to the Sn—X bonds (N1—Sn1—X1 = 165.8°). As a result of the intermolecular contacts, viz. H⋯X and H⋯benzene interactions, the molecules are arranged in a three-dimensional supramolecular manner in the crystal structure.

Related literature

For related literature see Varga et al. (2001 ▶, 2005 ▶, 2006 ▶, 2007 ▶); Rotar et al. (2007 ▶); Emsley (1994 ▶); IUPAC (1979 ▶).

Experimental

Crystal data

[SnBr_0.65Cl_1.35(C₉H₁₂N)₂]
M _r = 486.89
Monoclinic,
a = 17.0221 (15) Å
b = 8.2387 (7) Å
c = 14.7510 (13) Å
β = 106.1050 (10)°
V = 1987.5 (3) Å³
Z = 4
Mo Kα radiation
μ = 2.78 mm⁻¹
T = 297 (2) K
0.32 × 0.25 × 0.11 mm

Data collection

Bruker SMART APEX CCD area-detector diffractometer
Absorption correction: multi-scan (SAINT-Plus; Bruker, 2000 ▶) T _min = 0.452, T _max = 0.738
6916 measured reflections
1746 independent reflections
1693 reflections with I > 2σ(I)
R _int = 0.035

Refinement

R[F ² > 2σ(F ²)] = 0.027
wR(F ²) = 0.060
S = 1.24
1746 reflections
108 parameters
H-atom parameters constrained
Δρ_max = 0.36 e Å⁻³
Δρ_min = −0.47 e Å⁻³

Data collection: SMART (Bruker, 2000 ▶); cell refinement: SAINT-Plus (Bruker, 2000 ▶); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXTL (Bruker, 2001 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: DIAMOND (Brandenburg, 2006 ▶); software used to prepare material for publication: publCIF (Westrip, 2007 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536807063386/gd2029sup1.cif

e-64-00m45-sup1.cif^{(15.4KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536807063386/gd2029Isup2.hkl

e-64-00m45-Isup2.hkl^{(86.1KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C3—H3⋯Cg1ⁱⁱ	0.93	3.19	3.78 (1)	123
C4—H4⋯Cl1ⁱⁱ/Br1ⁱⁱ	0.93	2.87	3.798 (5)	173
C6—H6⋯Cl1ⁱⁱⁱ/Br1ⁱⁱⁱ	0.93	3.02	3.710 (3)	132

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Symmetry code: (ii) Inline graphic , , , (iii) , , . Cg1 is the centroid of the benzene ring C1–C6.

Acknowledgments

Financial support from the National University Research Council (CEEX 63/2006) is greatly appreciated. We also thank the National Center for X-Ray Diffraction, Cluj-Napoca, for help with the solid-state structure determination.

supplementary crystallographic information

Comment

During our work on hypervalent organotin(IV) compounds with the [2-(Me₂NCH₂)C₆H₄]Sn fragment (Varga et al., 2001, 2005, 2006, 2007, Rotar et al. 2007), the title compound (I) was isolated. It contains two 2-(Me₂NCH₂)C₆H₄ units bonded to a tin atom which lies on a twofold axis of the space group C2/c. The compound exhibits substitutional disorder of both halide atoms bonded to the Sn with chlorine being the major (1.35) and the bromine the minor (0.65) component.

The structure of [2-(Me₂NCH₂)C₆H₄]₂SnCl₂ was also determined (Varga et al., 2001) and is isomorphous with the title compound. Both have space group C2/c; the cell constants as well as the volume differ slightly (0.39% increase for the title compound) as the result of the presence of a different halide in the molecular unit.

The molecules of the compound feature a metal atom strongly coordinated by two nitrogen atoms of the pendant arms [Sn—N1 = 2.64 (1) Å; the Sn—N distance exceeds the sum of the covalent radii for the corresponding atoms, Σ_cov(Sn,N) = 2.1 Å (Emsley, 1994)] trans to an Sn–halogen bond (N1—Sn1—X1 = 165.8°). This results in a (C,N)₂SnX₂ (X = Cl/Br) core in the title compound with a trans-SnC₂ fragment, while the N and X atoms are cis positions (Fig. 1). The octahedral geometry around the Sn atom is distorted from the ideal geometry as a consequence of the small 'bite' of the pendant arm ligand [C1—Sn1—N1 = 71.4°] and the steric repulsion between the organic groups bonded to the Sn atoms. All these features are similar to the corresponding dichloride.

As a result of the intramolecular coordination of the nitrogen to the tin atom a five-membered SnC₃N ring is formed. This ring is not planar but is folded along the Sn(1)···C_methylene axis with the N atom out of the best plane defined by the residual SnC₃, thus inducing planar chirality, with the phenyl ring as chiral plane and the nitrogen as pilot atom (IUPAC, 1979). Indeed, the compound crystallizes as a racemate, i.e. a mixture of R_N1R_N1ⁱand S_N1S_N1ⁱ [symmetry code: (i) 2 - x, y, 0.5 - z].

In the crystal of the title compound intermolecular interactions, i.e. hydrogen bond type interactions and H···phenyl interactions (Fig. 2), give rise to a supramolecular array. If only chlorine is considered than layers are built of the same type of isomer [H4···X1ⁱⁱ = 2.87 Å, H3···Cg1ⁱⁱ = 3.19 Å; symmetry code: (ii) -1/2 + x, 1/2 + y, z] along the ab plane (Fig. 3). If bromine is taken into account, than alternating parallel layers of R_N1R_N1ⁱand S_N1S_N1ⁱ isomers are bridged through weak H6···X1ⁱⁱⁱ [3.02 Å; symmetry code: (iii) 2 - x, 1 - y, 1 - z] interactions resulting in a three-dimensional supramolecular architecture (Fig. 4).

Experimental

The title compound was isolated as a by-product of the reaction between [2-(Me₂NCH₂)C₆H₄]SnCl₂ and [2,6-(Me)₂C₆H₃]MgBr, due to partial halide exchange.