Ethene Activation and Catalytic Hydrogenation by a Low-Valent Uranium Pentalene Complex

摘要

The reaction of the uranium(III) complex [U(η~8-Pn~(††)(η~5-Cp*)] (1) (Pn~(††) = C_8H_4(1,4-Si~iPr_3)_2, Cp* = C_5Me_5) with ethene at atmospheric pressure produces the ethene-bridged diuranium complex [{(η~8-Pn~(††))(η~5-Cp*)U}_2(μ-η~2:η~2-C_2H_4)] (2). A computational analysis of 2 revealed that coordination of ethene to uranium reduces the carbon—carbon bond order from 2 to a value consistent with a single bond, with a concomitant change in the formal uranium oxidation state from +3 in 1 to +4 in 2. Furthermore, the uranium— ethene bonding in 2 is of the δ type, with the dominant uranium contribution being from f—d hybrid orbitals. Complex 2 reacts with hydrogen to produce ethane and reform 1, leading to the discovery that complex 1 also catalyzes the hydrogenation of ethene under ambient conditions.