Protonation Behavior of a Tetrahydrido Molybdenum(IV) Complex with Organic and Inorganic Acids

The reaction of [MoH4(depe)2] (1) (depe=1,2-bis(diethylphosphino)ethane) with different proton sources (HPtBu3+, C6H5COOH, C6F5COOH, H2SO4) was investigated. Whereas complete conversion of 1 into its protonated form is observed in the presence of the phosphonium salt, [MoH5(depe)2]+ only transiently forms upon treatment with the other acids. Further reactivity of the pentahydride complex is indeed noticed with the conjugated base, typically resulting in the formation of neutral (C6F5COOH, H2SO4) or cationic (PhCOOH) molybdenum dihydride complexes. The compounds were characterized by NMR spectroscopy and X-ray crystallographic studies were performed when suitable crystals were obtained. Protonation of polyhydride complexes: conjugated base matters! The protonation of a neutral molybdenum(IV) tetrahydride complex was investigated using a range of proton sources. Whereas simple acid-base process was achieved in the case of a phosphonium, subsequent reactivity of the resulting cationic pentahydride species with conjugated base was typically observed.image