Metathesis of a U imido complex: a route to a terminal U sulfide.

Herein, we report the synthesis and characterisation of the first terminal uranium(v) sulfide and a related U trithiocarbonate complex supported by sterically demanding tris(-butoxy)siloxide ligands. The reaction of the potassium-bound U imido complex, [U(NAd){OSi(OBu)}K] (), with CS led to the isolation of perthiodicarbonate [K(18c6)][CS] (), with concomitant formation of the U complex, [U{OSi(OBu)}], and S[double bond, length as m-dash]C[double bond, length as m-dash]NAd. In contrast, the reaction of the U imido complex, [K(2.2.2-cryptand)][U(NAd){OSi(OBu)}] (), with one or two equivalents of CS afforded the trithiocarbonate complex, [K(2.2.2-cryptand)][U(CS){OSi(OBu)}] (), which was isolated in 57% yield, with concomitant elimination of the admantyl thiocyanate product, S[double bond, length as m-dash]C[double bond, length as m-dash]NAd. Complex is likely formed by fast nucleophilic addition of a U terminal sulfide intermediate, resulting from the slow metathesis reaction of the imido complex with CS, to a second CS molecule. The addition of a solution of HS in thf (1.3 eq.) to afforded the first isolable U terminal sulfide complex, [K(2.2.2-cryptand)][US{OSi(OBu)}] (), in 41% yield. Based on DFT calculations, triple-bond character with a strong covalent interaction is suggested for the U-S bond in complex .