Synthesis, structure and NMR studies of trinuclear Mo3S4 clusters coordinated with dithiophosphate and chiral carboxylate ligands

Abstract

New chiral cluster complexes containing (S)-mandelate and (S)-phenyllactate ligands, [Mo₃S₄(dtp)₃(μ-(S)-mandelate)(py)] (1) and [Mo₃S₄(dtp)₃(μ-(S)-phenyllactate)(py)], were prepared from [Mo₃S₄(dtp)₃(μ-dtp)(H₂O)] (dtp = (EtO)₂PS₂) by ligand substitution. The crystal structures of 1 and 2 were determined by X-ray diffraction. Detailed variable-temperature ³¹P{¹H} and ¹H NMR studies of solutions of 1 and 2 in non-coordinating solvents (CDCl₃, CD₂Cl₂) demonstrated three dynamic processes at the Mo–Py coordination site: diastereomer interconversion [(PS) to (MS)] which is inhibited at low temperatures; pyridine rotation around the Mo–py bond (180°-flip), and pyridine exchange in the presence of added pyridine. Activation parameters for all exchange processes have been estimated.