Formation, characterization, and structural studies of novel thiosemicarbazone palladium(II) complexes. Crystal structures of [{Pd[C6H4C(Et)=NN=C(S)NH2]}(4)], [Pd{C6H4C(Et)=NN=C(S)NH2}(PMePh2)] and [{Pd[C6H4C(Et)=NN=C(S)NH2]}(2)-(mu-Ph2PCH2PPh2)]

The reaction of thiosemicarbazones 4-MeC6H4C(Me)=NN(H)C(=S)NH2 a, C6H5C(Et) =NN(H)C(=S)NH2 b and 4-MeC6H4C(Me)=NN(H)C(S)NHMe c with K-2[PdCl4] led to t etranuclear palladium(II) compounds, [{Pd[4-MeC6H3C(Me)=NN=C(S)NH2]}(4)], 1 a, [{Pd[C6H4C(Et)=NN=C(S)NH2]}(4)] 1b, and [{Pd[4-MeC6H3C(Me)=NN=C(S)NHMe]} (4)] 1c; the ligands are tridentate through the [C,N,S] atoms and they are deprotonated at the NH group. The Pd-S-chelating bond is sufficiently stron g for the complexes to undergo reactions with nucleophiles without bond cle avage. The molecular structure of 1b has been determined by single-crystal diffraction, confirming the formation of the tetranuclear moieties. Hydroge n bonding N ... H and S ... H links Pd-4 clusters into strands in the solid state. Reaction of 1a and 1b with phosphines gave mono- and di-nuclear spe cies, 2a, 2b, 3b and 5a, 5b, respectively. Treatment with 1,1'-bis(diphenyl phosphino)ferrocene led to trimetallic compounds 6a and 6b. The molecular s tructure of 3b has been determined by X-ray crystallography; dimer units ar e present through N ... H hydrogen bonds. The reaction of 2b with hydrochlo ric acid resulted in a 1:1 electrolyte, 4b, with NH and C=S groups. Alterna tively, treatment of 1a, 1b and 1c with strong chelating phosphines produce d mononuclear compounds with only cleavage of the Pd-S-bridging bonds, 7a, 7b, 7c and 8c with the diphosphine monodentate; 7a and 7b were obtained wit h the dinuclear species 7a' and 7b', respectively, as impurities, where the bidentate phosphine ligand bridges two metallated units. The crystal struc ture of one such compound, 7b', with a bridging bis(diphenylphosphino)metha ne ligand, is also described.