Synthesis of novel binuclear palladium-thallium carboxylates of the type PdTl(O2CR)5 and their structural characterization based on observation of J(203,205T1-1H) and J(203,205T1-13C)

Abstract

Reactions of palladium(II) carboxylates with thallium(III) carboxylates in toluene yield complexes of the type PdTl(O{2}CR){5} (I), R = Me, Et, i-Pr, or PdTl(O{2}CR){2}(O{2}CR'){3}(II), R = Me, Et, i-Pr, Ph; R' = Me, Et, i-Pr. Substitution of the ligands in PdTl(O{2}CMe){5} by free carboxylic acid has shown to be a second preparative route for compounds of type I. No reaction was observed for Pd(O{2}CMe){2} with Hg(O{2}CMe){2}, PhHg(O{2}CMe) or Ag(O{2}CMe) nor was any reaction observerd between {Pd(O{2}CMe)(C{6}H{4}NNC{6}H{5})}{2} and Tl(O{2}CMe){3}. Reaction of Pd(O{2}CME){2} with Hg(O{2}C-i-Pr){2} yields Hg(O{2}CMe)(O{2}C-i-PR).The PdTl(O{2}CR){5} complexes are the first examples of heterobinuclear palladium compounds lacking CO or phosphine ligands. Interaction of PdTl(O{2}CR){5} with CO or phosphines leads to a breakdown of the binuclear unit. On the basis of }1{H and }1{}3{ C NMR spectra, which reveal coupling of the thallium nucleus with the respective carbon and hydrogen atoms, a structure is proposed which contains four carboxylato ligands bridging the PdTl unit and one apical ligand bonded to thallium. This structure does not involve a direct Pd-to-Tl bond. The dynamic }1{H and }1{}3{C NMR spectra show in solution the occurrence of two distinct processes, i.e. dissociation of the apical ligand and exchange of bridging and apical ligands.