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Photochemical Route to Actinide-Transition Metal Bonds: Synthesis, Characterization and Reactivity of a Series of Thorium and Uranium Heterobimetallic Complexes

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posted on 05.03.2014 by Ashleigh L. Ward, Wayne W. Lukens, Connie C. Lu, John Arnold
A series of actinide–transition metal heterobimetallics has been prepared, featuring thorium, uranium, and cobalt. Complexes incorporating the binucleating ligand N­[ο-(NHCH2PiPr2)­C6H4]3 with either Th­(IV) (4) or U­(IV) (5) and a carbonyl bridged [Co­(CO)4] unit were synthesized from the corresponding actinide chlorides (Th: 2; U: 3) and Na­[Co­(CO)4]. Irradiation of the resulting isocarbonyls with ultraviolet light resulted in the formation of new species containing actinide–metal bonds in good yields (Th: 6; U: 7); this photolysis method provides a new approach to a relatively unusual class of complexes. Characterization by single-crystal X-ray diffraction revealed that elimination of the bridging carbonyl and formation of the metal–metal bond is accompanied by coordination of a phosphine arm from the N4P3 ligand to the cobalt center. Additionally, actinide–cobalt bonds of 3.0771(5) Å and 3.0319(7) Å for the thorium and uranium complexes, respectively, were observed. The solution-state behavior of the thorium complexes was evaluated using 1H, 1H–1H COSY, 31P, and variable-temperature NMR spectroscopy. IR, UV–vis/NIR, and variable-temperature magnetic susceptibility measurements are also reported.