Uranium(IV) Thio‐ and Selenoether Complexes: Syntheses, Structures, and Computational Investigation of U−ER2 Interactions

Rigid thioether- and selenoether-containing pincer proligands H[AS₂ ${}^{\mathrm{Ph}{}_2}$ ] (1) and H[ASe₂ ${}^{\mathrm{Ph}{}_2}$ ] (2) were synthesized, and deprotonation provided the potassium salts [K(AS₂ ${}^{\mathrm{Ph}{}_2}$ )(dme)] (3) and [K(ASe₂ ${}^{\mathrm{Ph}{}_2}$ )(dme)₂ ] (4). Reaction of two equivalents of 3 or 4 with [UI₄ (dioxane)₂ ] afforded the uranium thioether complex [(AS₂ ${}^{\mathrm{Ph}{}_2}$ )₂ UI₂ ] (5) and the first example of a uranium-selenoether complex, [(ASe₂ ${}^{\mathrm{Ph}{}_2}$ )₂ UI₂ ] (6). X-ray structures revealed distorted square antiprismatic geometries in which the AE₂ ${}^{\mathrm{Ph}{}_2}$ ligands are κ³ -coordinated. The nature of the U-ER₂ 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.