Antisymbiosis. Preferential coordination of anionic oxygen versus neutral sulfur donor atoms of methylsulfanyl- or methylsulfinyl-acetato, 2-benzoato and 2-phenolato to the cis-PtII(PPh3)2 and PtII(dppe) residues

The interaction of an excess of the title ligands L- with the cis-Pt(phos)2 moieties gives compounds a-b cis-[Pt(L-O)2(phos)2] (a, phos = P(Ph)3; b, phos = ½ dppe) in which O- is preferred to S-coordination. Such preference is confirmed by the the fact that the same products are obtained by reaction of excess of L- with the previously reported a-d complexes [Pt(L-O,S)(phos)2]+, (c, phos = PPh3, d, phos = dppe) for which chelate ring opening occurs with rupture of Pt-S rather than Pt-O bonds. Compounds a can be obtained also by oxidative addition of HL to [Pt(PPh3)3]. The Pt-O bonds in compounds a-d are stable towards substitution by Me2SO, pyridine and tetramethylthiourea. Substitution of L’s occurs with N,N’-diethyldithiocarbamate, which forms a very stable chelate with Pt(II). Thiourea and N,N’-dimethylthiourea also react, because they give rise to cyclometallated products [Pt(phos)2(NRC(S)NHR)]+ (R = H, CH3), with one ionised thioamido group, as revealed by an X-ray investigation of [Pt(PPh3)2(NHC(S)NH2)]+. The preference of O versus S coordination, as well as the stability of the Pt-O bonds, are discussed in terms of antisymbiosis.