The Influence of Substituents at C² Carbon Atom of Thiosemicarbazones {R(H)C²=N³‐N²(H)‐C¹(=S)‐N¹H₂} on their Dentacy in Pt^II/Pd^II Complexes: Synthesis, Spectroscopy, and Crystal Structures

Abstract

Abstract The coordination chemistry of platinum(II) with a series of thiosemicarbazones {R(H)C 2 =N 3 ‐N 2 (H)‐C 1 (=S)‐N 1 H 2 , R = 2‐hydroxyphenyl, H 2 stsc; pyrrole, H 2 ptsc; phenyl, Hbtsc} is described. Reactions of trans ‐PtCl 2 (PPh 3 ) 2 precursor with H 2 stsc (or H 2 ptsc) in 1 : 1 molar ratio in the presence of Et 3 N base yielded complexes, [Pt(η 3 ‐ O, N 3 , S‐stsc)(PPh 3 )] ( 1 ) and [Pt(η 3 ‐ N 4 , N 3 , S‐ptsc)(PPh 3 )] ( 2 ), respectively. Further, trans ‐PtCl 2 (PPh 3 ) 2 and Hbtsc in 1 : 2 (M : L) molar ratio yielded a different compound, [Pt(η 2 ‐ N 3 , S‐btsc)(η 1 ‐S‐btsc)(PPh 3 )] ( 3 ). Complex 1 involved deprotonation of hydrazinic (‐N 2 H‐) and hydroxyl (‐OH) groups, and stsc 2− is coordinating via O, N 3 , S donor atoms, while complex 2 involved deprotonation of hydrazinic (‐N 2 H‐) and ‐N 4 H groups and ptsc 2− is probably coordinating via N 4 , N 3 , S donor atoms. Reaction of PdCl 2 (PPh 3 ) 2 with Hbtsc‐Me {C 6 H 5 (CH 3 )C 2 =N 3 ‐N 2 (H)‐C 1 (=S)‐N 1 H 2 } yielded a cyclometallated complex [Pd(η 3 ‐C, N 3 , S‐btsc‐Me)(PPh 3 )] ( 4 ). These complexes have been characterized with the help of analytical data, spectroscopic techniques {IR, NMR ( 1 H, 31 P), U.V} and single crystal X‐ray crystallography ( 1 , 3 and 4 ). The effects of substituents at C 2 carbon of thiosemicarbazones on their dentacy and cyclometallation are emphasized.