The influence of substituents at C2 carbon atom of thiosemicarbazones {R(H)C2=N3-N2(H)-C 1(=S)-N1H2} on their dentacy in Pt II/PdII complexes: Synthesis, spectroscopy, and crystal structures

Article abstract of DOI:10.1002/zaac.200700538

The coordination chemistry of platinum(II) with a series of thiosemicarbazones {R(H)C²=N³-N²(H)-C ¹(=S)-N¹H₂, R = 2-hydroxyphenyl, H ₂stsc; pyrrole, H₂ptsc; phenyl, Hbtsc} is described. Reactions of trans-PtCl₂(PPh₃)₂ precursor with H₂stsc (or H₂ptsc) in 1:1 molar ratio in the presence of Et₃N base yielded complexes, [Pt(η³- O, N³, S-stsc)(PPh₃)] (1) and [Pt(η³- N⁴, N ³, S-ptsc)(PPh₃)] (2), respectively. Further, trans-PtCl₂(PPh₃)₂ and Hbtsc in 1:2 (M:L) molar ratio yielded a different compound, [Pt(η²- N³, S-btsc)(η¹-S-btsc)(PPh₃)] (3). Complex 1 involved deprotonation of hydrazinic (-N²H-) and hydroxyl (-OH) groups, and stsc^2- is coordinating via O, N³, S donor atoms, while complex 2 involved deprotonation of hydrazinic (-N²H-) and -N ⁴H groups and ptsc^2- is probably coordinating via N ⁴, N³, S donor atoms. Reaction of PdCl ₂(PPh₃)₂ with Hbtsc-Me {C₆H ₅(CH₃)C²=N³-N²(H)-C ¹(=S)-N¹H₂} yielded a cyclometallated complex [Pd(η³-C, N³, S-btsc-Me)(PPh₃)] (4). These complexes have been characterized with the help of analytical data, spectroscopic techniques {IR, NMR (¹H, ³¹P), U.V} and single crystal X-ray crystallography (1, 3 and 4). The effects of substituents at C² carbon of thiosemicarbazones on their dentacy and cyclometallation are emphasized.