New cyclometallated platinum(II) compounds with thiosemicarbazones: crystal and molecular structure of [Pt{4-MeC6H3C(Me)NNC(S)NH2}(PPh3)]

Treatment of the thiosemicarbazones 3-CH3(CH2)5OC6H4C(Me)NN(H)C(S)NH2 (a), 4-MeC6H4C(Me)NN(H)C(S)NH2 (b), C6H5C(Et)NN(H)C(S)NH2 (c), C6H5C{CH3(CH2)10}NN(H)C(S)NH2 (d) and 4-MeC6H4C(Me)NN(H)C(S)NHMe (e) with K2[PtCl4] gives tetranuclear platinum(II) compounds 1a–1e with deprotonation of the NH group and with the ligand acting as a terdentate [C,N,S] moiety. Reaction of 1a–1e with PPh3 and of 1a with P(4-MeOC6H4)3 yielded mononuclear species 2a–2e and 3a, respectively. Treatment of 1a with the diphosphines Ph2PCH2PPh2 (dppm), Ph2P(CH2)2PPh2 (dppe), Ph2P(CH2)3PPh2 (dppp), Ph2P(CH2)4PPh2 (dppb), Ph2P(CH2)5PPh2 (dpppe), Ph2P(CH2)6PPh2 (dpph), and 1,1′-ferrocenebis(diphenylphosphine) (dppf) gives dinuclear compounds 4a–10a. In all cases the PdSchelating bond is strong enough to withstand reaction with the phosphorus ligands without bond cleavage. The molecular structure of 2b has been determined by X-ray crystallography. Mononuclear units are held together by hydrogen bonding, forming dimers in the solid state.