Metathesis of a U-V imido complex: a route to a terminal U-V sulfide
Résumé
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(OtBu)(3)\(4)kappa] (4), with CS2 led to the isolation of perthiodicarbonate [kappa(18c6)](2)[C2S6] (6), with concomitant formation of the U-IV complex, [U\OSi(OtBu)(3)\(4)], and S=C=NAd. In contrast, the reaction of the UV imido complex, [kappa(2.2.2-cryptand)][U(NAd) \OSi(OtBu)(3)\(4)] (5), with one or two equivalents of CS2 afforded the trithiocarbonate complex, [kappa(2.2.2-cryptand)][ U(CS3)\OSi(OtBu)(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 UV terminal sulfide intermediate, resulting from the slow metathesis reaction of the imido complex with CS2, to a second CS2 molecule. The addition of a solution of H2S in thf (1.3 eq.) to 4 afforded the first isolable U-V terminal sulfide complex, [kappa(2.2.2-cryptand)][US\OSi(OtBu)(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.