Metathesis of a UV imido complex: a route to a terminal UV sulfide

The metathesis reaction of a U V imido complex supported by sterically demanding tris( tert -butoxy)siloxide ligands with CS 2 afforded a terminal U V thiocarbonate but metathesis with H 2 S afforded the first example of a terminal U V sulfide. Herein, we report the synthesis and characterisation of the first terminal uranium( v ) sulfide and a related U V trithiocarbonate complex supported by sterically demanding tris( tert -butoxy)siloxide ligands. The reaction of the potassium-bound U V imido complex, [U(NAd){OSi(O t Bu) 3 } 4 K] ( 4 ), with CS 2 led to the isolation of perthiodicarbonate [K(18c6)] 2 [C 2 S 6 ] ( 6 ), with concomitant formation of the U IV complex, [U{OSi(O t Bu) 3 } 4 ], and S Created by potrace 1.16, written by Peter Selinger 2001-2019 C NAd. In contrast, the reaction of the U V imido complex, [K(2.2.2-cryptand)][U(NAd){OSi(O t Bu) 3 } 4 ] ( 5 ), with one or two equivalents of CS 2 afforded the trithiocarbonate complex, [K(2.2.2-cryptand)][U(CS 3 ){OSi(O t Bu) 3 } 4 ] ( 7 ), which was isolated in 57% yield, with concomitant elimination of the admantyl thiocyanate product, S C NAd. Complex 7 is likely formed by fast nucleophilic addition of a U V terminal sulfide intermediate, resulting from the slow metathesis reaction of the imido complex with CS 2 , to a second CS 2 molecule. The addition of a solution of H 2 S in thf (1.3 eq.) to 4 afforded the first isolable U V terminal sulfide complex, [K(2.2.2-cryptand)][US{OSi(O t Bu) 3 } 4 ] ( 8 ), in 41% yield. Based on DFT calculations, triple-bond character with a strong covalent interaction is suggested for the U–S bond in complex 7 .