The anomalous electrochemical behaviour of the tetrathioether macrocyclic complexes [MoX2(Me8[16]aneS4)](X = Cl or Br): the X-ray structures of [MoBr2(Me8[16]aneS4)]+/0 and modulation of redox potentials in conformers of the [MoBr2(Me8[16]aneS4)]+/0 system

Abstract

The anomalous redox properties of [MoX₂(Me₈[16]aneS₄)], X - Cl or Br, reported previously are rationalised, the authentic reduction of the dibromide occuring at E_1/2=–2.87 V versus ferrocinium–ferrocene to give an unstable 17-electron anion which reacts with carbon monoxide and dinitrogen; low temperature cyclic voltammetry shows the [MoBr₂(Me₈[16]aneS₄)]^+/0 system to be fluxional and this is explained by a metal ‘in- or out-of-plane’ deformation accompanying conformational rearrangement of the macrocyclic ligand, X-ray crystallography showing the neutral dibromide to have the ‘all-up’ arrangement of the macrocyclic tetrathioether ligand rather than the ‘up–up–down–down’ conformation of the one-electron oxidised species.