Multinuclear NMR study of some organoplatinum complexes containing multifunctional azines as chelating ligands

H-1-detected indirect NMR techniques were used to determine N-15 and Pt-195 NMR parameters for a series of organoplatinum(IV) complexes and one platinum(II) complex containing nitrogen-based azobispyridine, bispyridyltetrazine, and bipyrimidine ligands. The inverse technique permitted the detection of small (4)J(Pt,H) and (5)J(Pt,H) long-range couplings and the acquisition of N-15 NMR data in natural isotopic abundance via J(N,H) intra- and inter-ligand couplings, but failed in cases where coherence transfer is quenched by rapid relaxation of the metal atom. In one case, analysis of satellite patterns in a set of H-1,N-15, H-1, Pt-195 and H-1,C-13 correlation spectra allowed a positive sign to be determined for (1)J(Pt,N-15). Qualitative arguments are presented to explain the observed N-15 coordination shifts in complexes with different azine ligands in terms of azine-M dative bond formation and LnM-azine back-donation. Copyright (C) 2004 John Wiley Sons, Ltd.