Palladium(II) Complexes with Dithiomalonamide and N,N′-Diphenyldithiomalonamide

Abstract

Dithiomalonamide (Hdtma) and N,N′-diphenyldithiomalonamide (Hdpma) form diamagnetic square-planar complexes PdL2 and PdL2•2DMF. For these complexes a [PdS4] coordination was suggested by their electronic and i.r. spectra. The splitting orbital parameters, Δ1, indicates that these anionic ligands assume an intermediate position in the spectrochemical series of sulfur donors. These ligands also form Pd(HL)2X2 (X = Cl, Br, I, ClO4) and PdHLX2 (X = Cl, Br, I) complexes in which spectroscopic evidence suggests an S,N bidentate ligand coordination, forming six-membered rings. ν(PdN) and ν(PdS) are tentatively assigned. For Pd(Hdpma)2X2 complexes from the far i.r. and electronic spectra we propose a cis-PdN2S2 configuration. The Δ1 parameters in the six-membered ring Pd(HL)2X2 complexes indicate a ligand strength greater than in the analogous S,N coordinated five-membered ring complexes of dithiooxamides and show an inversion of the order found in Ni(HL)2X2 (HL = Hdtma, Hdpma) complexes. In PdHLX2 complexes the presence of two bands assignable to Vasym(PdX) and Vsym(PdX) supports a cis-halogen configuration.