Patterns of nuclear spin coupling in species with platinum–tin bonds: a comparison of phosphorus and tin

Abstract

A range of heteronuclear magnetic multiple-resonance experiments involving ¹H, ³¹P, ¹¹⁹Sn, ¹⁹⁵Pt, and ²⁰⁷Pb was used to determine the absolute signs of nuclear spin-coupling constants for platinum(II) complexes with PR₃[R = alkyl, aryl, or alkoxy] and SnCl₃^–, SnPh₃^–, or PbPh₃^– as ligands. The signs of and trends in the reduced coupling constants ¹K(EX) and ²K(EX) for E = Sn(Pb) closely parallel those for E = P, but the actual magnitudes for E = Sn(Pb) are much larger than expected when the mean excitation-energy approximation is used as a basis for the Fermi-contact contribution. This is attributed to greater s character for the hybrid orbital used by E to form the E–Pt bond when E = Sn(Pb) which affects the mutual polarizability and hence K(EX).