Fourier transform NMR investigations on organotin compounds : V. Coupling constants and chemical shifts in simple tetraorganotins

Abstract

Carbon-13 NMR data are reported and discussed for 32 simple tetraorganotins R n SnR′ 4- n ( n = 0–4) in which the tin atom is four-coordinate. It is found that the value of 1 J(SnC) in compounds R 4Sn depends on the effective nuclear charge at tin; in mixed organotins Bent's postulate is apparently verified, and in a number of cases coupling constants can again be correlated with Taft σ★ constants for the alkyl groups. The values of 1 J(Sn C H 2) in benzyltin compounds are clearly anomalous. Long-range tin—carbon coupling constants are discussed. The chemical shifts of the carbons in methyl groups bound to tin provide a second useful probe for estimating the electron-withdrawing or electron-releasing power of alkyl and other groups bound to the tin atom.