Formation of organometallic hydroxo and oxo complexes by oxidation of transition metal hydrides in the presence of water. X-ray structures of [CpMo(OH)(PMe3)(3)][BF4] and [CpMo(O)(PMe3)(2)][BF4]

The decomposition of complex [CpMoH(PMe3)(3)](+), 1(+), in wet, weakly coor dinating solvents (THF and acetone) leads to the formation of the Mo(III) h ydroxo compound [CpMo(OH)(PMe3)(3)][BF4], 2, and the Mo(IV) oxo compound [C pMo(O)(PMe3)(2)][BF4], 3. Both of these have been characterized by X-ray cr ystallography. The formation of these products is rationalized by a mechani sm which involves water coordination followed by multiple steps of tandem o xidation and deprotonation reactions. The proposed [CpMoH(PMe3)(3)(H2O)](2) intermediate is observed by NMR spectroscopy. EPR monitoring of the oxida tion of 1 with ferrocenium shows also the formation of a species characteri zed by a binomial triplet resonance and interpreted as the neutral Mo(III)- oxo complex CpMo(O)(PMe3)(2), 4. The proposed mechanism is in harmony with the previously investigated mechanism of decomposition of 1(+) in dry solve nts and with the coupled proton and electron transfer processes that relate aqua, hydroxo, and oxo species in the chemistry of Mo enzymes. Computation al studies at the DFT level were carried out on a model system where the PM e3 ligand was replaced by PH3. Their results are consistent with the propos ed mechanism.