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

New triangular Mo and W cluster complexes incorporating (S)-lactic acid (HLac), [Mo3S4(mu-Lac)(dtp)(3)(py)] (1) and [W3S4(mu-Lac)(dtp)(3)(py)] (2), were prepared [dtp = (EtO)(2)PS2]. Analogous synthetic procedures were adapted for the synthesis of cuboidal Mo3NiS4 to yield [Mo-3(Nipy)S-4(py)(mu-OAc)( dtp) 3(py)] (3). The crystal structures of 1 and 3 were determined. A detailed variable-temperature P-31{H-1} and H-1 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.