Oxidation of TpRMo(NO)(L)(CO) where TpR = tris(pyrazolyl)borate (Tp) or tris(3,5-dimethylpyrazolyl)borate (Tp*) and L = 1-methylimidazole (1-MeIm), 1,3-dimethylimidazol-2-ylidene (NHC), 4-dimethylaminopyridine (4-DMAP), and PMe3 using mild oxidants such as cumene hydroperoxide, t-butyl hydroperoxide, or O2 give η2-carbon dioxide complexes, TpRMo(NO)(L)(η2-CO2). The reactivity of these complexes has been explored. Reduction of TpRMo(NO)(L)(η2-CO2) back to TpRMo(NO)(L)(CO) can be accomplished using chemical reductants including LiBH4. Another promising route of reactivity involves the dissociation L to allow coordination of an alkene. However, all of the above η2-CO2 complexes require high temperature (&gt;100 oC) and long reactions times (&gt;1 d) to displace L. However, upon oxidation complexes featuring a bulkier L, such as TpMo(NO)(PPh3)(CO) do not result in isolable η2-CO2 complexes. However, when L = PPh2Me and PPhMe2, the η2-CO2 complexes become accessible. The reactivity of these complexes with alkenes such as ethane, cyclohexene and styrene has been explored. In addition, TpMo(NO)(PPh2Me)(η2-alkene) complexes have been prepared and exposed to CO2 under high pressure.

Synthesis and reactivity of molybdenum carbon dioxide complexes

2019 Spring National Meeting

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