Cyclometallated thiosemicarbazone palladium(II) compounds: The first crystal and molecular structures of mononuclear complexes with a η 1-diphosphine ligand

Abstract

Treatment of the thiosemicarbazones 2-XC 6H 4C(Me) NN(H)C( S)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-XC 6H 3C(Me) NN C(S)NHR}] 4 ( 1a– 1d). Reaction of 1a– 1d with the diphosphines Ph 2PCH 2PPh 2 (dppm), Ph 2P(CH 2) 2PPh 2 (dppe), Ph 2P(CH 2) 3PPh 2 (dppp) or trans-Ph 2PCH CHPPh 2 ( trans-dpe) in 1:2 molar ratio gave the dinuclear cyclometallated complexes [{Pd[2-XC 6H 3C(Me) NN C(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-XC 6H 3C(Me) NN C(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.