M(CO)4 (M=Mo or W) complexes of 2,6-bis(methylthiomethyl)pyridine (L1) and 2,6-bis(p-tolylthiomethyl)pyridine (L2): a dynamic NMR study

Article abstract of DOI:10.1016/0022-328X(94)05192-E

The hybrid S/N/S donor ligands 2,6-bis(methylthiomethyl)pyridine (L¹) and 2,6-bis(p-tolylthiomethyl)pyridine (L²) react with the (M = Mo or W) compounds to form complexes of general formula (M = Mo, L = L²; M = W, L = L¹ or L²), where both L¹ and L² act in a S/N bidentate chelate fashion.In solution, these complexes undergo three fluxional processes, viz. inversion at the coordinated S atom, S¹-S² switching, and combined inversion and S¹-S² switching, leading to an interconversion of the four possible permutational isomers.Energy barriers for all three processes have been evaluated by standard one-dimensional band-shape analysis techniques.The mechanism of the S¹-S² switch is discussed. Keywords: Molybdenum; Tungsten; Fluxionality; Nuclear magnetic resonance