Fourier transform nuclear magnetic resonance investigations of organotin compounds. Part 6. Tin-119 and carbon-13 nuclear magnetic resonance. Spectra of hexaorganoditins and octaorganotritins

Abstract

In a series of closely related hexa-alkylditins or octaorganotritins, the magnitude of ¹J(Sn–Sn) varies greatlyaccording to the nature of the alkyl groups; in the ditin series a linear relationship is found between ¹J(Sn–Sn) and the sum of the Taft σ* constants of the alkyl groups. Application of this relation to the tri-tins allows estimation of σ* values for the trialkyltin groups: similar values for σ* are obtained by considering the values of ¹J(Sn–C) in dior tri-tins. σ* Values for Me₃Si and Me₃Ge have also been obtained. Replacementof alkyl groups in a hexa-alkylditin by electronegative acetoxy groups causes a large increase in ¹J(Sn–Sn); replacement of alkyl groups by phenyl groups causes only small variations. The ¹¹⁹Sn and ¹³C chemical shifts and long-range coupling constants are discussed. The larger hexa-alkylditins and octa-alkyltritins exhibit relatively large negative nuclear Overhauser effects, which may be partially eliminated by adding chromium tris(acetylacetenate) to the solution under investigation.