Further orthometalated dinuclear palladium(iii) compounds with bridging N,S-donor ligands

Abstract

New dinuclear palladium(III) compounds of general formula Pd₂[(C₆H₄)PPh₂]₂[N–S]₂Cl₂, N–S being 2-mercaptopyridinate, 3a; 2-mercapto-6-methylpyridinate, 3b; 2-quinolinethiolate, 3c; 2-mercaptopyrimidinate, 3d; 1-methyl-1H-imidazole-2-thiolate, 3e; 1-methyl-1H-benzimidazole-2-thiolate, 3f; 2-mercaptobenzothiazolate, 3g and 5-mercapto-1-methyltetrazolate, 3h have been obtained by oxidation with PhICl₂ of the corresponding palladium(II) counterparts. The stability of the new compounds has been studied by ³¹P NMR spectroscopy from 200 to 298 K. Compounds 3f–h were relatively stable until room temperature and they have been synthesized and characterized by ³¹P, ¹H and ¹³C NMR spectroscopy at 223 K. Compound 3h was also structurally characterized by single X-ray diffraction methods at 150 K showing a Pd–Pd distance of 2.6334(6) Å. A topological charge density analysis has also been performed in order to obtain information on the nature of the bonding in these new palladium(II) and (III) compounds. The contribution of the sulphur p orbitals to the HOMO orbitals in the oxidized compounds allows greater stabilization.