Cyclometallated thiosemicarbazone palladium(II) compounds: The first crystal and molecular structures of mononuclear complexes with a η1-diphosphine ligand

Treatment of the thiosemicarbazones 2-XC6H4C(Me)double bond; length as m-dashNN(H)C(double bond; length as m-dashS)NHR (R = Me, X = F, a; R = Et, X = F, b; R = Me, X = Cl, c; R = Et, X = Br, d) with potassium tetrachloropalladate(II) in ethanol, lithium tetrachloropalladate(II) in methanol or palladium(II) acetate in acetic acid, as appropriate, gave the tetranuclear cyclometallated complexes [Pd{2-XC6H3C(Me)double bond; length as m-dashNNdouble bond; length as m-dashC(S)NHR}]4 (1a–1d). Reaction of 1a–1d with the diphosphines Ph2PCH2PPh2 (dppm), Ph2P(CH2)2PPh2 (dppe), Ph2P(CH2)3PPh2 (dppp) or trans-Ph2PCHdouble bond; length as m-dashCHPPh2 (trans-dpe) in 1:2 molar ratio gave the dinuclear cyclometallated complexes [{Pd[2-XC6H3C(Me)double bond; length as m-dashNNdouble bond; length as m-dashC(S)-NHR]}2(μ-diphosphine-P,P)] (2a–5a, 3b, 3d, 4c, 5c). Reaction of 1a, 1b with the short-bite or long-bite diphosphines, dppm or cis-dpe, in a 1:4 molar ratio gave the mononuclear cyclometallated complexes [Pd{2-XC6H3C(Me)double bond; length as m-dashNNdouble bond; length as m-dashC(S)NHR}(diphosphine-P)] (6a, 6b, 7a). The molecular structure of ligand a and of complexes 1a, 3d, 5a, 5c, 6a, 6b and 7a have been determined by X-ray diffraction analysis. The structure of complex 7a shows that the long-bite cis-bis(diphenylphosphino)ethene phosphine appears as monodentate with an uncoordinated phosphorus donor atom.