Electrochemical oxidation and protonation of a bridging amide ligand at a dinuclear metal–sulfur site†

Abstract

The electrochemical oxidation of the amide complex [Mo₂(cp)₂(µ-SMe)₃(µ-NH₂)] 1 (cp = η⁵-C₅H₅) has been investigated in tetrahydrofuran (thf) and MeCN electrolytes by cyclic voltammetry, controlled-potential electrolysis and coulometry. The two-electron oxidation of 1 leads to the release of a proton and to the formation of the imide derivative [Mo₂(cp)₂(µ-SMe)₃(µ-NH)]⁺2. In MeCN, this reaction is reversible. The protonation of 1 has been shown to produce a complex in which a NH₃ ligand is bound to a Mo centre; the protonated complex is stabilized by co-ordination of the anion of the acid, of the solvent or of a substrate to the neighbouring metal centre. The protonation performed in thf in the presence of chloride produces [Mo₂(cp)₂(µ-SMe)₃(µ-Cl)] which is the precursor of the amide complex 1. The final protonation product formed in MeCN is [Mo₂(cp)₂(µ-SMe)₃(MeCN)₂]⁺, which also is a precursor of 1. Therefore, these experiments allow the construction of a hydrazine disproportionation cycle.