Trimethylplatinum(IV) complexes of anionic O/O and N/O donor ligands: synthesis, NMR and fluxional behaviour

摘要

Reaction of pentane-2,4-dione, pyridine-2-carboxylic acid or pyridine-2,6-dicarboxylic acid with trimethylplatinum(IV) gives dimeric complexes of general formulate fac-[PtMe3L](2), in which the ionised ligand acts in a chelating and a bridging fashion. High-resolution solid-state Pt-195 NMR data shows that the two platinum atoms are equivalent; the chemical shielding anisotropy and the principal components of the shielding tensor are reported. The complexes are soluble in co-ordinating solvents, yielding monomeric species of general formulae fac-[PtMe3L(solvent)], which are fluxional. The pyridine adducts, fac-[PtMe3L(py)] (L = pentane-2,4-dionato or pyridine-2-carboxylato), are also stereochemically non-rigid. The energetics of the dynamic processes have been studied by standard H-1 NMR band shape analysis techniques; Delta G( double dagger) (298 K) is in the range 69-86 kJ mol(-1). Solid-state C-13, and solution-state C-13 and Pt-195 NMR data are also reported. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. [References: 33]