Synthesis, characterization and solid state structures of thiosemicarbazone palladacycles: Influence of hydrogen bonding in the molecular arrangement

Treatment of the thiosemicarbazones 4-FC6H4C(Me)double bond; length as m-dashNN(H)C(double bond; length as m-dashS)NHR, (R = Me, a; Ph, b) and 2-ClC6H4C(Me)double bond; length as m-dashNN(H)C(double bond; length as m-dashS)NHR (R = Ph, c) with lithium tetrachloropalladate(II) in methanol or palladium(II) acetate in acetic acid gave the tetranuclear cyclometallated complex [Pd{4-FC6H3C(Me)double bond; length as m-dashNNdouble bond; length as m-dashC(S)NHR}]4 (1a, 1b) and [Pd{2-ClC6H3C(Me)double bond; length as m-dashNNdouble bond; length as m-dashC(S)NHPh}]4 (1c). Reaction of these tetramers with the diphosphines dppe, t-dppe, dppp or dppb in a 1:2 molar ratio gave the dinuclear cyclometallated complexes [(Pd{4-FC6H3C(Me)double bond; length as m-dashNNdouble bond; length as m-dashC(S)NHR})2(μ-Ph2P(CH2)nPPh2)], (n = 2, 2a, 2b; 3, 4a, 4b; 4, 5a, 5b), [(Pd{4-FC6H3C(Me)double bond; length as m-dashNNdouble bond; length as m-dashC(S)NHPh})2(μ-Ph2PCHdouble bond; length as m-dashCHPPh2)], (3a, 3b) and [(Pd{2-ClC6H3C(Me)double bond; length as m-dashNNdouble bond; length as m-dashC(S)NHR})2(μ-Ph2P(CH2)nPPh2)], (n = 2, 2c, 2d; 3, 4c, 4d; 4, 5c, 5d), [(Pd{2-ClC6H3C(Me)double bond; length as m-dashNNdouble bond; length as m-dashC(S)NHPh})2(μ-PPh2CHdouble bond; length as m-dashCHPPh2)], (3c, 3d). The X-ray crystal structure of the ligand b and the complexes 3c, 4a and 4d were determined. The structures of complexes 4a and 4d show that the different disposition of the chain cyclometallated of the thiosemicarbazones (in the same orientation or in the opposite one) is due to the different H bonds produced.