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

A series of actinide–transition metal heterobimetallics has been prepared, featuring thorium, uranium, and cobalt. Complexes incorporating the binucleating ligand N­[<i>ο</i>-(NHCH<sub>2</sub>P<sup>i</sup>Pr<sub>2</sub>)­C<sub>6</sub>H<sub>4</sub>]<sub>3</sub> with either Th­(IV) (<b>4</b>) or U­(IV) (<b>5</b>) and a carbonyl bridged [Co­(CO)<sub>4</sub>]<sup>−</sup> unit were synthesized from the corresponding actinide chlorides (Th: <b>2</b>; U: <b>3</b>) and Na­[Co­(CO)<sub>4</sub>]. Irradiation of the resulting isocarbonyls with ultraviolet light resulted in the formation of new species containing actinide–metal bonds in good yields (Th: <b>6</b>; U: <b>7</b>); 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 N<sub>4</sub>P<sub>3</sub> 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 <sup>1</sup>H, <sup>1</sup>H–<sup>1</sup>H COSY, <sup>31</sup>P, and variable-temperature NMR spectroscopy. IR, UV–vis/NIR, and variable-temperature magnetic susceptibility measurements are also reported.