Cuboidal Mo3S4 and Mo3NiS4 Complexes Bearing Dithiophosphates and Chiral Carboxylate Ligands: Synthesis, Crystal Structure and Fluxionality

Abstract

New triangular Mo and W cluster complexes incorporating (S)-lactic acid (HLac), [Mo3S4(μ-Lac)(dtp)3(py)] (1) and [W3S4(μ-Lac)(dtp)3(py)] (2), were prepared [dtp = (EtO)2PS2]. Analogous synthetic procedures were adapted for the synthesis of cuboidal Mo3NiS4 to yield [Mo3(Nipy)S4(py)(μ-OAc)(dtp)3(py)] (3). The crystal structures of 1 and 3 were determined. A detailed variable-temperature 31P{1H} and 1H NMR study of compounds 1 and 3 indicated fluxional behaviour in non-coordinating solvents (CDCl3, CD2Cl2 and CDCl2CDCl2). A number of dynamic processes were identified involving the Mo–py site that include configuration inversion [(P) to (M)], hindered Mo–N rotation and pyridine exchange. Experiments with deuterated pyridine revealed a faster substitutional lability of Mo–py compared with Ni–py.