Cuboidal Mo 3 S 4 and Mo 3 NiS 4 Complexes Bearing Dithiophosphates and Chiral Carboxylate Ligands: Synthesis, Crystal Structure and Fluxionality

New triangular Mo and W cluster complexes incorporating ( S )‐lactic acid (HLac), [Mo 3 S 4 (μ‐Lac)(dtp) 3 (py)] ( 1 ) and [W 3 S 4 (μ‐Lac)(dtp) 3 (py)] ( 2 ), were prepared [dtp = (EtO) 2 PS 2 ]. Analogous synthetic procedures were adapted for the synthesis of cuboidal Mo 3 NiS 4 to yield [Mo 3 (Nipy)S 4 (py)(μ‐OAc)(dtp) 3 (py)] ( 3 ). The crystal structures of 1 and 3 were determined. A detailed variable‐temperature 31 P{ 1 H} and 1 H NMR study of compounds 1 and 3 indicated fluxional behaviour in non‐coordinating solvents (CDCl 3 , CD 2 Cl 2 and CDCl 2 CDCl 2 ). 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.