Metal-Ligand Multiple Bonds: Catalytic Dehydrogenation of Volatile Alkanes, Methane Olefination, and Super Bases
Abstract. Converting natural resources such as methane and ethane, the main components of natural and shale gas, into more value-added materials under mild conditions and using base metals, is one of the main objectives in my research program. I will start by presenting the reactivity of a transient titanium alkylidyne (PNP)Ti≡CtBu (pincer PNP = N[2-P(CHMe2)2-4-methylphenyl]2–), specifically how this species forms and engages in intermolecular C-H activation and functionalization reactions. Such a system can dehydrogenate methane, and react with C2-C8 alkanes selectively by activating at the a- and b-positions. In the case of linear alkanes C4-C8, we only observe formation of the terminal olefin adduct. A new catalytic cycle for transfer dehydrogenation of alkanes will be also introduced in addition to unique platforms to form kinetically stable Ti=CH2 moieties (titanium methylidene) that are relevant to our proposed catalytic cycle. I will also discuss a new transformation involving the room temperature conversion of methane to an olefin using a titanium alkylidene in cooperation with a redox-active ligand and how it compares to an electrophilic iridium system that can convert methane to ethylene with the aid of a phosphorus ylide reagent. The last component, if time permitted, will present the synthesis and reactivity of group 4 transition metal nitrides and how one can tune the basicity of the nitride ligand by shifting down the group.