3,3-Bls(halomethylstannyl)propyl Ethyl Sulfoxides. The Nature of Intramolecular Coordination in the Crystals and in Solution

The preparations of 3,3-bis(chlorodimethylstannyl)propyl ethyl sulfoxide, (Me₂ClSn)₂CHCH₂CH₂S(O)Et, and of 3,3-bis(dichloromethylstannyl)propyl ethyl sulfoxide, (MeCl2Sn) 2CHCH2CH2S(O)Et, are described. Structures of these compounds and of their bromo analogues have been determined by single-crystal X-ray diffraction. (Me₂ClSn)₂CHCH₂CH₂S(O)Et, 1, crystallizes in the triclinic space group PI with o = 7.002 (3) Å, b = 9.383 (5) Å, c = 13.771 (7) Å, α = 104.35 (4)°, β = 98.67 (4)°, γ = 90.37 (4)°, V = 865.7 (7) ų, and D_calcd = 1.867 g cm^-3 for Z = 2. Full-matrix best-squares refinement of positional and anisotropic temperature parameter converged at a conventional residual of 0.068 for 1306 independent reflections. (MeCl₂Sn)₂CHCH₂CH₂S(O)Et, 2, crystallizes in the triclinic space group P1 with a = 9.099 (3) Å, b = 9.477 (3) Å, c = 10.476(4) Å, α = 113.34 (2)°, β = 99.68 (2)°, γ = 91.87 (2)°, V = 812.7 (7) ų, and = 2.155 g cm^-3 for Z = 2; R = 0.032 for 1842 reflections. (MeBr₂Sn)₂CHCH₂CH₂S(O)Et, 3, crystallizes in the space group PI with a = 7.074 (2) Å, b = 9.325 (3) Å, c = 14.070 (6) Å, α = 77.45 (2)°, β = 81.03 (3)°, γ = 88.23 (2)°, V = 894.7 (7) ų, and = 2.136 g cm^-3 for Z = 2; R = 0.078 for 1739 reflections. (MeBr₂Sn)₂CHCH₂CH₂S(O)Et, 4, crystallizes in the monoclinic space group P2₁/n with o = 8.965 (3) Å, b = 17.887 (7) ų, c = 11.166 (4) Å, β = 102.29 (2)°, V = 1749.5 (6) ų, = 2.677 g cm^-3, and Z = 4; R = 0.076 for 1128 reflections. The structures of 1 and 3 consist of discrete binuclear units with nonequivalent Sn atoms bridged symmetrically by a carbon of the propyl ethyl sulfoxide group and unsymmetrically by one or two halide atoms, depending on the degree of halide substitution. On the other hand, 2 and 4 exhibit halide bridging between two adjacent binuclear units to produce a loosely associated bimolecular or tetranuclear unit. The propyl ethyl sulfoxide ligand is coordinated through the sulfoxide oxygen donor to one tin atom in all cases. IR, ¹H NMR, ¹³C NMR, and ¹¹⁹Sn NMR studies, coupled with the structural results, suggest that the oxygen of the sulfoxide group undergoes rapid coordinative exchange between the two tin atoms in each compound in solution.