The reaction of the uranium(III) complex [U(eta(8)-Pn(dagger dagger))(eta(5)-Cp*)] (1) (Pn(dagger dagger) = C8H4(1,4-(SiPr3)-Pr-i)(2), Cp* = C5Me5) with ethene at atmospheric pressure produces the ethene-bridged diuranium complex [{(eta(8)-Pn(dagger dagger))(eta(5)-Cp*)U}(2)(mu-eta(2):eta(2)-C2H4)] (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 delta 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.