Catalytic visible light-driven alkane dehydrogenation by a di-uranyl germanotungstate
Published Web Location
https://doi.org/10.1039/d6sc01626j
Abstract
The dehydrogenation of alkanes to alkenes is an appealing strategy for upgrading abundant hydrocarbons, yet it is constrained by the inherent challenge of cleaving two inert C(sp3)-H bonds with selectivity and without overoxidation. We report a cooperative photocatalytic dehydrogenation of unactivated cycloalkanes under visible light irradiation enabled by a new dinuclear uranyl complex supported by an oxidatively stable germanotungstate, [NBu n 4]8[(UO2)2(GeW10O34(µ2-OH)2)2]·(CH3)2CO (1). The uranyl complex catalytically converts cyclooctane to cyclooctene under ambient conditions with a TON per molecule of 44 and 9,10-dihydrophenanthrene to phenanthrene with a TON of 73 per molecule, using 1 mol% 1 in MeCN solution, under 427 nm irradiation, using [S2O8]2- or chloranil (C6Cl4O2) as a sacrificial oxidant. The value of preorganization of two uranyl centers to yield the product of double hydrogen atom abstraction (HAA) is discussed in comparison with uranyl nitrate, [UO2(NO3)2(H2O)2]·4H2O, the most widely studied uranyl photocatalyst, which is inactive for this reaction. A direct hydrogen atom transfer (d-HAT) mechanism with two HAA processes is proposed as trans-di-deuterated substrate (9S, 10S)-9,10-dihydrophenanthrene-9,10-d2 (C14H10D2) exclusively forms d1 phenanthrene from abstraction of an H and a D atom from the same face.
Many UC-authored scholarly publications are freely available on this site because of the UC's open access policies. Let us know how this access is important for you.