Reduction of [(C₅Me₅)₂Mo₂O₅] and [(C₅Me₅)₂Mo₂O₄] in methanol/water/trifluoroacetate solutions investigated by combined on-line electrochemistry/electrospray-ionization mass spectrometry

Complexes [Cp*₂Mo₂O₅] (Cp* = η⁵-C₅Me₅) and [Cp*₂Mo₂O₄] were investigated by combined on-line electrochemical (EC) reduction and electrospray-ionization mass spectrometry (ESI-MS) techniques in a trifluoroacetic acid buffered water/methanol solution. The reduction products at the larger negative potentials are identical for both compounds. The studies reveal the existence of a wide range of previously unknown di- and trinuclear Mo^V, Mo^IV, Mo^III, and mixed-valence complexes that were identified on the basis of their masses and characteristic isotope patterns. The structures of the initial compounds and the product of electroreduction with m/z = 713-729 were supported by in situ MSⁿ experiments that allowed the elucidation of the fragmentation pathway for the collision-induced dissociation.