Uranium versus Thorium: Synthesis and Reactivity of [<i>η</i><sup>5</sup>‐1,2,4‐(Me<sub>3</sub>C)<sub>3</sub>C<sub>5</sub>H<sub>2</sub>]<sub>2</sub>U[<i>η</i><sup>2</sup>‐C<sub>2</sub>Ph<sub>2</sub>]
Deqiang Wang, Wanjian Ding, Guohua Hou, Guofu Zi, Marc D. Walter
Abstract
Abstract The synthesis, electronic structure, and reactivity of a uranium metallacyclopropene were comprehensively studied. Addition of diphenylacetylene (PhC≡CPh) to the uranium phosphinidene metallocene [ η 5 ‐1,2,4‐(Me 3 C) 3 C 5 H 2 ] 2 U=P‐2,4,6‐ t Bu 3 C 6 H 2 ( 1 ) yields the stable uranium metallacyclopropene, [ η 5 ‐1,2,4‐(Me 3 C) 3 C 5 H 2 ] 2 U[ η 2 ‐C 2 Ph 2 ] ( 2 ). Based on density functional theory (DFT) results the 5f orbital contributions to the bonding within the metallacyclopropene U‐( η 2 ‐C=C) moiety increases significantly compared to the related Th IV compound [ η 5 ‐1,2,4‐(Me 3 C) 3 C 5 H 2 ] 2 Th[ η 2 ‐C 2 Ph 2 ], which also results in more covalent bonds between the [ η 5 ‐1,2,4‐(Me 3 C) 3 C 5 H 2 ] 2 U 2+ and [ η 2 ‐C 2 Ph 2 ] 2− fragments. Although the thorium and uranium complexes are structurally closely related, different reaction patterns are therefore observed. For example, 2 reacts as a masked synthon for the low‐valent uranium(II) metallocene [ η 5 ‐1,2,4‐(Me 3 C) 3 C 5 H 2 ] 2 U II when reacted with Ph 2 E 2 (E=S, Se), alkynes and a variety of hetero‐unsaturated molecules such as imines, ketazine, bipy, nitriles, organic azides, and azo derivatives. In contrast, five‐membered metallaheterocycles are accessible when 2 is treated with isothiocyanate, aldehydes, and ketones.