Studies of Monothiomalonamide and its Palladium(II) and Platinum(II) Complexes

A project related to the crystal engineering of hydrogen bonded coordination complexes has been initiated and our first results are presented here. The cis and trans forms of monothiomalonamide (LH ) have been fully characterized by vibrational spectroscopy, thermal techniques and single-crystal X-ray diffraction. The cis form crystallizes in the monoclinic space group P2 /c and the trans form in the monoclinic space group C2/c. The respective lattice constants are a = 5.602(3), b = 9.055(2), c = 10.945(5)Å , β = 101.29(2)" (cis-LH ) and a = 20.336(7), b = 4.317(1), c = 12.432(5) Å, β = 92.16(1)" (trans-LH ). The new complexes [Pd(LH ]X (X = Cl, Br), [Pt(LH ]X (X = Br, I), [PdX (LH ] (X = Cl, Br, I) and [PtX (LH ] (X = Cl, I) were prepared and characterized by elemental analyses and spectroscopic (IR, far-IR, Raman) studies. All data are discussed in terms of the nature of bonding in conjunction with assigned structures. The LH molecule behaves as a monodentate ligand binding through the sulfur atom. Monomeric square planar structures are assigned for the metal complexes in the solid state; the 1:2 complexes have the trans geometry. A detailed comparison of the new complexes with the corresponding monothiooxamide complexes is also presented.