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

Abstract

Treatment of the thiosemicarbazones 4-FC 6H 4C(Me) NN(H)C( S)NHR, (R = Me, a; Ph, b) and 2-ClC 6H 4C(Me) NN(H)C( S)NHR (R = Ph, c) with lithium tetrachloropalladate(II) in methanol or palladium(II) acetate in acetic acid gave the tetranuclear cyclometallated complex [Pd{4-FC 6H 3C(Me) NN C(S)NHR}] 4 ( 1a, 1b) and [Pd{2-ClC 6H 3C(Me) NN C(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-FC 6H 3C(Me) NN C(S)NHR}) 2(μ-Ph 2P(CH 2) n PPh 2)], ( n = 2, 2a, 2b; 3, 4a, 4b; 4, 5a, 5b), [(Pd{4-FC 6H 3C(Me) NN C(S)NHPh}) 2(μ-Ph 2PCH CHPPh 2)], ( 3a, 3b) and [(Pd{2-ClC 6H 3C(Me) NN C(S)NHR}) 2(μ-Ph 2P(CH 2) n PPh 2)], ( n = 2, 2c, 2d; 3, 4c, 4d; 4, 5c, 5d), [(Pd{2-ClC 6H 3C(Me) NN C(S)NHPh}) 2(μ-PPh 2CH CHPPh 2)], ( 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.