Reactivity of a Lewis base-supported uranium terminal imido metallocene towards small molecules

Abstract

The Lewis base-supported uranium terminal imido metallocene [η⁵-1,2,4-(Me₃Si)₃C₅H₂]₂UN(p-tolyl)(dmap) (1) readily reacts with various small molecules such as internal alkynes, isothiocyanates, thioketones, amidates, organic nitriles and imines, chlorosilanes, copper iodide, diphenyl disulfide, organic azides and diazoalkane derivatives. For example, treatment of 1 with PhCCCCPh and PhNCS forms metallaheterocycles originating from a [2 + 2] cycloaddition to yield [η⁵-1-(p-tolyl)NC(Ph)CHCC(Ph)CH₂Si(Me)₂-2,4-(Me₃Si)₂C₅H₂][η⁵-1,2,4-(Me₃Si)₃C₅H₂]U (2) and [η⁵-1,2,4-(Me₃Si)₃C₅H₂]₂U[N(p-tolyl)C(NPh)S](dmap) (3), respectively. The reaction of 1 with the thioketone Ph₂CS forms the known uranium sulfido complex [η⁵-1,2,4-(Me₃Si)₃C₅H₂]₂US(dmap) (4), which reacts with a second molecule of Ph₂CS to give the disulfido compound [η⁵-1,2,4-(Me₃Si)₃C₅H₂]₂U(S₂CPh₂) (5). The imido moiety also promotes deprotonation reactions as illustrated in the reactions with the amide PhCONH(p-tolyl), the nitrile PhCH₂CN and the imine (p-tolyl)₂CNH to form the bis-amidate [η⁵-1,2,4-(Me₃Si)₃C₅H₂]₂U[OC(Ph)N(p-tolyl)]₂ (7), and the iminato complexes [η⁵-1,2,4-(Me₃Si)₃C₅H₂]₂U[N(p-tolyl)C(CH₂Ph)NH](NCCHPh) (8) and [η⁵-1,2,4-(Me₃Si)₃C₅H₂]₂U[NH(p-tolyl)][NC(p-tolyl)₂] (9), respectively. Addition of PhSiH₂Cl to 1 yields [η⁵-1,2,4-(Me₃Si)₃C₅H₂]₂U(Cl)[N(p-tolyl)SiH₂Ph] (10). In contrast, the uranium(V) imido complexes [η⁵-1,2,4-(Me₃Si)₃C₅H₂]₂UN(p-tolyl)(I) (11) and [η⁵-1,2,4-(Me₃Si)₃C₅H₂]₂UN(p-tolyl)(SPh) (12), may be isolated upon addition of CuI or Ph₂S₂ to 1, respectively. Uranium(VI) bis-imido metallocenes [η⁵-1,2,4-(Me₃Si)₃C₅H₂]₂UN(p-tolyl)(NR) (R = p-tolyl (13), mesityl (14)) and [η⁵-1,2,4-(Me₃Si)₃C₅H₂]₂UN(p-tolyl)[NN(9-C₁₃H₈)] (15) are accessible from 1 on exposure to RN₃ (R = p-tolyl, mesityl) and 9-diazofluorene, respectively. Complexes 2, 3, 5, and 7–15 were characterized by various spectroscopic techniques and, in addition, compounds 2, 3, 5, and 7–13 were structurally authenticated by single-crystal X-ray diffraction analyses.