Investigations into bis(triphenylphosphine)copper(I) complexes with cyclic derivatives of methylpyruvate thiosemicarbazones

The syntheses of four compounds, obtained by the reaction of methylpyruvate thiosemicarbazone (Hmpt) and its methyl (Me-Hmpt) and allyl (Allyl-Hmpt) derivatives with bis(triphenylphosphine)copper(l) acetate, are reported. The compounds [Cu(PPh3)(2)(pt(c))(Hpt(c))]center dot H2O (1), [Cu(PPh3)(2)(Me-pt(c))] (2), [Cu-2(PPh3)(2)mu-S(Me-pt)mu-S(Me-pt(c))]center dot H2O (3) and [Cu(PPh3)(2)(Allyl-pt(c))] (4) [H(2)pt = pyruvic acid thiosemicarbazone and Hptc = cyclized pyruvic acid thiosemicarbazone, Me = methyl and Allyl are radical substituents on the amino nitrogen] were characterized by elemental analysis, IR, H-1 NMR, and by X-ray crystallography. Compound 3 was also studied by EPR because of the presence in the compound of two copper atoms in two different oxidation states. During the complexation reaction, the thiosemicarbazone ligands tend to undergo a cyclization reaction that leads to the formation of a six-member heterocyclic ring. All four compounds present the [Cu(PPh3)(2)](+) fragment and constant but different coordination situations. Compound 1 contains two cyclic ligand molecules, one protonated and the other deprotonated, bound as monodentate through the sulfur. Compounds 2 and 4 present a single deprotonated cyclic SN bidentate ligand molecule, while compound 3 contains copper(I) and copper(II), and two ligand molecules, one of which is linear and behaves as SNO tridentate and the other is cyclic and behaves as bridging mu SN. (C) 2010 Elsevier Ltd. All rights reserved.