Synthesis and characterization of platinum(IV) complexes with N,S and S,S heterocyclic ligands

The reactions of [PtMe3(OAc)(bpy)] (4) with the N,S and S,S containing heterocycles, pyrimidine-2-thione (pymtH), pyridine-2-thione (pytH), thiazoline-2-thione (tztH) and thiophene-2-thiol (tptH), resulted in the formation of the monomeric complexes [PtMe3(-κS)(bpy)] ( = pymt, 5; pyt, 6; tzt, 7; tpt, 8), where the heterocyclic ligand is coordinated via the exocyclic sulfur atom. In contrast, in the reactions of [PtMe3(OAc)(Me2CO)x] (3, x = 1 or 2) with pymtH, pytH, tztH and tptH dimeric complexes [{PtMe3(μ-)}2] (μ- = pymt, 9; pyt, 10; tzt, 11) and the tetrameric complex [{PtMe3(μ3-tpt-κS)}4] (12), respectively, were formed. The complexes were characterized by microanalyses, 1H and 13C NMR spectroscopy and negative ESI-MS (12) measurements. Single-crystal X-ray diffraction analysis of [PtMe3(pymt-κS)(bpy)] (5) exhibited a conformation where the pymt ligand lies nearly perpendicular to the complex plane above the bpy ligand that was also confirmed by quantum chemical calculations on the DFT level of theory.