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

Treatment of the thiosemicarbazones 4-FC6H4C(Me)NN(H)C(S)NHR, (R = Me, a; Ph, b) and 2-ClC6H4C(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-FC6H3C(Me)NNC(S)NHR}]4 (1a, 1b) and [Pd{2-ClC6H3C(Me)NNC(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)NNC(S)NHR})2(μ-Ph2P(CH2)nPPh2)], (n = 2, 2a, 2b; 3, 4a, 4b; 4, 5a, 5b), [(Pd{4-FC6H3C(Me)NNC(S)NHPh})2(μ-Ph2PCHCHPPh2)], (3a, 3b) and [(Pd{2-ClC6H3C(Me)NNC(S)NHR})2(μ-Ph2P(CH2)nPPh2)], (n = 2, 2c, 2d; 3, 4c, 4d; 4, 5c, 5d), [(Pd{2-ClC6H3C(Me)NNC(S)NHPh})2(μ-PPh2CHCHPPh2)], (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.

Graphical abstractDinuclear cyclometallated palladium thiosemicarbazone compounds with tertiary diphosphines may adopt cisoid or transoid geometries depending on the inter- or intramolecular nature of the hydrogen bonding established between atoms.Figure optionsDownload full-size imageDownload as PowerPoint slide