Geminal Bis(haloorganostannanes) and Their Complexation as Mono- and Bidentate Lewis Acids with Dimethyl Sulfoxide

Six (chloromethylstannyl)methanes with structures CH₂(SnMenCl₃_n)(SnMemCl3-m) with n = 0-3 and m = 0-2 have been prepared by chlorine-methyl exchange from bis(trimethylstannyl)methane or bis-(trivinylstannyl)methane. Four 2,2-bis(chloromethylstannyl)propanes have been similarly prepared from 2,2-bis(trimethylstannyl)propane. Correlations between ¹H and ¹³C magnetic resonance parameters have been examined. The effects of dimethyl sulfoxide (Me₂SO) on the ¹H NMR parameters of the chloro-stannanes have been examined as a source of information on complexation. Seven complexes with Me₂SO have been prepared, and the structures of CH₂(SnMeCl₂)-(SnMe₂Cl)(Me₅SO)λ⁴, CH₂(SnMeCl₂)₂(₂Me₂SO)λ⁵, and CH₂(SnCl₃)₂(₄Me₂SO)λ⁷ have been determined by X-ray diffraction. In the first of these, the oxygen of the Me₂SO bridges the two tins which display distorted trigonal-bipyramidal geometry; in the second, the oxygens of each Me₂SO act as bridges between the tins which display distorted octahedral geometry; in the third, the oxygens do not bridge and the CH₂ group serves as a common apex for the octehedra of two hexacoordinate tins. Pertinent features of the structures are discussed. Compound 4 crystallizes in the space group P1 with a = 7.551 (2) A, b = 7.945 (2) A, c = 13.354 (3) A, a = 80.63 (2), β = 89.13 (2), 7 = 72.96 (2), and Z = 2. The structure solution and refinement were based on 1609 reflections with F0 > 6σ(F0) to give a discrepancy factor of 0.045. Compound 5 crystallizes in the orthorhombic space group Pbnm with a = 9.821 (2) A, b = 12.411 (2) A, c = 15.540 (3), and Z = 4. Refinement based on 1109 reflections with Fo > 6σ(Fo) converged at 0.048. Compound 7 crystallizes in the monoclinic space group C2/c with a = 20.998 (5) A, b = 7.925 (3) A, c = 16.535 (4), β = 98.79 (3), and Z = 4. Refinement using 1277 reflections with Fo > 6σ(Fo) yielded R = 0.034.