Synthesis and structural characterization of tridentate [C,N,S] thiosemicarbazone palladacycles. Crystal and molecular structures of [Pd{3-FC6H3C(Me)NNC(S)NHMe}]4, [Pd{4-FC6H3C(Me)NNC(S)NHEt}]4 and [(Pd{2-BrC6H3C(Me)NNC(S)NHPh})2(μ-Ph2P(CH2)2PPh2)]

Reaction of the thiosemicarbazones 3-FC6H4C(Me)NN(H)C(S)NHME a, 4-FC6H4C(Me)NN(H)C(S)NHEt b, and 2-BrC6H4C(Me)NN(H)C(S)NHPh c, with potassium tetrachloropalladate(II) in ethanol, lithium tetrachloropalladate(II) in methanol or palladium(II) acetate in acetic acid gave the tetranuclear cyclometallated complexes [Pd{3-FC6H3C(Me)NNC(S)NHMe}]41a, [Pd{4-FC6H3C(Me)NNC-(S)NHEt}]41b, and [Pd{2-BrC6H3C(Me)NNC(S)NHPh}]41c. Reaction of 1a–c with the diphosphines Ph2P(CH2)nPPh2 dppm (n = 1), dppe (n = 2), dppp (n = 3), dppb (n = 4) or Ph2PCHCHPPh2trans-dppe, in a 1:2 molar ratio gave the dinuclear phosphine-bridged complexes [(Pd{XC6H3C(Me)NNC(S)NHR})2(μ-Ph2P(CH2)nPPh2)] 2a–c, 3a–c, 4a–c, 5a–c (n = 1–4) and [(Pd{XC6H3C(Me)NNC(S)NHR})2(μ-Ph2PCHCH-PPh2)] 6a–c. Treatment of 1a–c with PPh2CH2PPh2, dppm, in a 1:4 molar ratio gave the mononuclear cyclometallated complexes [Pd{XC6H3C(Me)NNC(S)NHR}-(Ph2PCH2PPh2-P)] 7a–c; however, the diphosphines with n ⩾ 2 failed to give the analogous reaction. The molecular structures of 1a, 1b and 3c have been determined by X-ray diffraction analysis and the intra- and intermolecular interactions are discussed.

Graphical abstractThe preparation and characterization of tetranuclear and dinuclear thiosemicarbazone palladium(II) complexes have been carried out. The crystal structure analysis for 1a and 1b shows intra- and intermolecular interactions, which in the former case lead to formation of chains along the bisector of the a/b axes, as well as along the b axis.Figure optionsDownload full-size imageDownload as PowerPoint slide