1H nuclear magnetic resonance study of (d–p)π interactions in stannanes containing unsaturated systems

Abstract

The proton chemical shift and long range proton–tin coupling constants relative to the methyl group of a number of methylaryl stannanes of general formula MeSnR₃, where R is an unsaturated group, were derived. The results show that (d–p)π interactions between empty d orbitals of tin and the electronic π system of R groups should be small, and in any case the n.m.r. parameters seem to be mainly influenced by an inductive effect from the unsaturated system. Also, the spectra recorded in a solvent which can give co-ordination compounds such as dimethyl sulphoxide, afford no evidence of a major disposal of d orbitals for (d–p)π interactions. An analogous situation seems to be present in the corresponding compounds of mercury MeHgR. Examination of some para-substituted tetra-aryltin compounds indicates that the tin atom also conjugates poorly with para-substituents through an aromatic ring.