Tin-119 NMR Studies on adduct formation and stereochemistry of organoyltin(IV)trihalides

Abstract

qazTin-119 and phosphorus-31 NMR spectra have been recorded for a series of adducts of RSnX 3 (R  Me, Ph; X  Cl, Br) with halide, tributylphosphine (P) and tributylphosphine oxide (L). The adducts were either 1:1 five coordinate or 1:2 six coordinate complexes. The tin-ll9 NMR spectra of mixtures of corresponding chloro and bromo complexes reveal, in most cases, all possible mixed halide species but much additional structural information is obtained from these spectra which could not be extracted from the spectra of individual compounds themselves. Thus in some cases, in the five coordinate species the Berry pseudorotation between isomers within a particular stoichiometry could be slowed on the NMR timescale which allowed a determination of the molecular structure. An equimolar mixture of [PhSnCl 5] 2− and [PhSnBr 5] 2− shows eleven of the twelve geometries possible for [PhSnCl x Br 5− x ] 2−. In the six coordinate series [RSnX 4P] − the tin-119 NMR spectra of the mixtures of [RSnCl 4P] − and [RSnBr 4P] − allow the geometry to be determined as trans. Application of the pairwise additivity model for calculation of the tin-119 chemical shift positions for the mixed halide systems are discussed.