Nuclear spin–spin coupling between tin and other directly bound elements

Abstract

Heteronuclear double-resonance experiments are used to determine the signs and magnitudes of the spin-coupling constants between tin and the directly bound elements boron, nitrogen, silicon, tin, tellurium, and tungsten in some trimethylstannyl derivatives. These and other coupling constants involving tin are compared with the corresponding couplings involving carbon and it is found that for X = H, B, C, F, Si, Sn, Te, and W, ¹K(Sn–X) is approximately nine times ¹K(C–X) whereas for X = N, P^III, P^v, and Se this is not so. For X = N and P^v the reduced couplings to carbon and tin are of opposite sign. The results are consistent with a molecular orbital theory which does not use the mean excitation energy approximation and, in general, it is concluded that the s-overlap integral β_{Sn – X} is smaller than β_{C – X} which leads to larger negative contributions to the mutual polarizability in the case of tin compounds.