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

2005-08-17T00:00:00Z (GMT) by Ingrid Castro-Rodriguez Karsten Meyer
The highly reactive, six-coordinate tris-aryloxide U(III) species, [((<sup>t-Bu</sup>ArO)<sub>3</sub>tacn)U] (<b>1</b>) reacts with CO<sub>2</sub> in a 2e<sup>-</sup> reduction to produce CO and a dinuclear U(IV/IV) μ-oxygen bridged complex [{((<sup>t-Bu</sup>ArO)<sub>3</sub>tacn)U}<sub>2</sub>(μ-O)] (<b>2</b>). This reaction proceeds via a dinuclear CO<sub>2</sub>-bridged intermediate <b>3</b>. Also, mononuclear <b>1</b> was treated with 1 atm of CO to yield dinuclear [{((<sup>t-Bu</sup>ArO)<sub>3</sub>tacn)U}<sub>2</sub>(μ-CO)] (<b>4</b>) with a CO ligand bridging two uranium ions in an unprecedented μ:η,η<sup>1</sup> fashion. The mixed-valent azido-bridged U(III/IV) complex <b>5</b> was synthesized from trivalent <b>1</b> and tetravalent [((<sup>t-Bu</sup>ArO)<sub>3</sub>tacn)U(N<sub>3</sub>)] and serves as an isostructural analogue of triatomic-bridged intermediate <b>3</b> as well as an electronic model for mixed-valent <b>4</b>.