Carbon Dioxide Reduction and Carbon Monoxide Activation Employing a Reactive Uranium(III) Complex

The highly reactive, six-coordinate tris-aryloxide U (III) species, ( (t-BuArO) 3tacn) U (1) reacts with CO2 in a 2e- reduction to produce CO and a dinuclear U (IV/IV) mu-oxygen bridged complex ( (t-BuArO) 3tacn) U2 (mu-O) (2). This reaction proceeds via a dinuclear CO2-bridged intermediate 3. Also, mononuclear 1 was treated with 1 atm of CO to yield dinuclear ( (t-BuArO) 3tacn) U2 (mu-CO) (4) with a CO ligand bridging two uranium ions in an unprecedented mu: eta1, eta1 fashion. The mixed-valent azido-bridged U (III/IV) complex 5 was synthesized from trivalent 1 and tetravalent ( (t-BuArO) 3tacn) U (N3) and serves as an isostructural analogue of triatomic-bridged intermediate 3 as well as an electronic model for mixed-valent 4.