STUDIES OF THE CIS-TRANS ISOMERISM OF SOME SQUARE-PLANAR PLATINUM(II) NITROIMIDAZOLE COMPLEXES

Cis-trans isomerism reactions of cis-Pt(MNZ)2X2 complexes, where MNZ is metronidazole [1-(2'-hydroxyethyl)-2-methyl-5-nitroimidazole] and X = Cl, Br or I, occur in both the solid-state and in solution, and were studied by differential scanning calorimetry and multinuclear NMR spectroscopy. For the solid-state process, enthalpies of isomerization ranged from -21 to -49 kJ mol-1. First order rate constants were determined from Pt-195 NMR measurements in solution; consideration of the effects of added halides and free ligand suggests that the reaction mechanism involves associative processes.