Correlation of nuclear magnetic resonance coupling constants with transition metal–ligand bond lengths in tertiary phosphine complexes

Abstract

N.m.r. coupling constants ¹J(M–P) are reported for complexes of W^IV, Pt^I, and Pt^IV. Results for ¹J(Pt–P) in the complexes [PtCl_4–n(R₃P)_n]^(n-2)+ and [PtCl_6–n(R₃P)_n]^(n–2)+(n= 1–3) are discussed in terms of the M.O. expression for the Fermi contact interaction. Interpretation of coupling constants in terms of the s-orbital bond order is supported by the correlation of bond lengths with ¹J(Pt–P) for Pt^II complexes and by the similarity of trends in bond lengths and M–P coupling constants in mer-tris(phosphine) complexes of W^IV, Rh^I, Rh^III, Pt^II, and Pt^IV. It is also shown that, for both ¹J(Pt–P) and ²J(PtCH), ratios of coupling constants in related Pt^IV and Pt^II complexes reflect bond-length differences in the two oxidation states.