Uranium(IV) Thio- and Selenoether Complexes: Syntheses, Structures, and Computational Investigation of U-ER Interactions.

Rigid thioether- and selenoether-containing pincer proligands H[AS ] (1) and H[ASe ] (2) were synthesized, and deprotonation provided the potassium salts [K(AS )(dme)] (3) and [K(ASe )(dme) ] (4). Reaction of two equivalents of 3 or 4 with [UI (dioxane) ] afforded the uranium thioether complex [(AS ) UI ] (5) and the first example of a uranium-selenoether complex, [(ASe ) UI ] (6). X-ray structures revealed distorted square antiprismatic geometries in which the AE ligands are κ -coordinated. The nature of the U-ER bonding in 5 and 6, as well as methyl-free analogues of 5 and 6 and a hypothetical ether analogue, was investigated computationally (including NBO, AIM, and ELF calculations) illustrating increasing covalency from O to S to Se.