LAUSR

Recent experimental work shows that the 18-electron molybdenum complexes (1,2,4-C5H2tBu3)Mo(PMe3)2H3 (CptBuMoH3) and (C5HiPr4)Mo(PMe3)2H3 (CpiPrMoH3) undergo oxidatively induced reductive elimination of dihydrogen (H2), slowly forming the 15-electron monohydride species in tetrahydrofuran and acetonitrile. The 17-electron [CptBuMoH3]+ derivative was stable enough to be characterized by X-ray diffraction, while [CpiPrMoH3]+ was not. Density functional theory calculations of the H2 elimination pathways for both complexes in the gas phase and in a continuum solvent model indicate that H2 elimination from [CpiPrMoH3]+ has a lower barrier than that from [CptBuMoH3]+. Further, a specific solvent association, which is stronger for [CptBuMoH3]+ than for [CpiPrMoH3]+, contributes to the stability of the former. In agreement with the experimental observations, the calculations predict that [CptBuMoH3]+ would be in a quartet state at room temperature and a doublet state at 4.2 K, while [CpiPrMoH3]+ is in a doublet state even at room temperature.