Thorium(IV)\nand Uranium(IV) Thioether and Selenoether\nComplexes: Synthesis and An–ER<sub>2</sub> (E = S, Se) Bonding\nComparison

Reactions of the rigid thioether- and selenoether-containing\nligand\nsalts [{Li(AE<sub>2</sub><sup>Ph2</sup>)}<sub>2</sub>] (E = S or Se;\nAE<sub>2</sub><sup>Ph2</sup> = 4,5-bis(phenylchalcogenido)-2,7,9,9-tetramethylacridanide)\nwith ThCl<sub>4</sub>(dme)<sub>2</sub> or UCl<sub>4</sub> (for E =\nSe) afforded the actinide chalcogenoether complexes [(AE<sub>2</sub><sup>Ph2</sup>)<sub>2</sub>ThCl<sub>2</sub>] (E = S (<b>1</b>), Se (<b>2</b>)), and [(ASe<sub>2</sub><sup>Ph2</sup>)<sub>2</sub>UCl<sub>2</sub>] (<b>3</b>). X-ray crystal structures\nof <b>1</b>–<b>3</b> revealed tetravalent actinide\ncations complexed to two κ<sup>3</sup>-coordinated AE<sub>2</sub><sup>Ph2</sup> ligands, with Th–ER<sub>2</sub> and U–ER<sub>2</sub> distances below the sum of the covalent radii. Complexes <b>1</b>–<b>3</b> provide extremely rare examples of\nthorium–thioether, thorium–selenoether, and uranium–selenoether\nbonds, and <b>1</b> and <b>2</b> contain the shortest\nknown Th–SR<sub>2</sub> and Th–SeR<sub>2</sub> distances.\nDFT and QTAIM calculations confirm the presence of significant An(IV)–ER<sub>2</sub> interactions in <b>1</b>–<b>3</b> and\nprovide insight into the extent of covalency in the An–ER<sub>2</sub> bonds.