Synthesis and characterisation of Pd(II), Pt(II) and Pt(IV) complexes of diphosphadithia ligands and the crystal structure of [Pt(L-1)](PF6)(2)center dot MeCN (L-1=Ph2P(CH2)(2)S(CH2)(2)S(CH2)(2)PPh2)

A series of square planar Pd(II) and Pt(II) complexes involving tetradentate diphosphadithia ligands has been prepared in high yield and characterised by IR, H-1, P-31{H-1} and Pt-195 NMR spectroscopy, mass spectrometry and microanalyses. [Pt(L-1)](2+) (L-1 = Ph2P(CH2)(2)S(CH2)(2)S(CH2)(2)PPh2) crystallises in the triclinic space group <P(1)over bar> (No. 2), with a = 12.644(8), b = 15.15(1), c = 10.368(6) Angstrom, alpha = 94.16(5), beta = 105.24(5), gamma = 86.53(5)degrees and Z = 2. The structure confirms the distorted square planar coordination at Pt(II), Pt-P = 2.261(2), 2.265(2), Pt-S = 2.341(2), 2.344(2) Angstrom. The geometry is rather strained, with the methylene groups all directed to one side of the coordination plane and the metal ion displaced out of the least squares P2S2 plane by 0.19 Angstrom in the opposite direction. Halogen oxidation (Cl-2 or Br-2) of the Pt(II) species yields the cationic Pt(IV) compounds [PtX2(L)](2+) as yellow (Cl) or orange (Br) species. P-31{H-1} and Pt-195 NMR studies confirm that the P2S2 ligation is retained, giving octahedral P2S2X2 coordination at Pt(IV), in which the relatively hard Pt(IV) centres are stabilised by a soft ligand donor set. (C) 1997 Elsevier Science S.A.