C-H Bond Activation by an Isolated Dinuclear U(III)/U(IV) Nitride

Synthetic studies of bimetallic uranium nitride complexes with the N(SiMe3)(2) ligand have generated a new nitride complex of U(III), which is highly reactive toward C-H bonds and H-2. Treatment of the previously reported U(IV)/U(IV) nitride complex [Na(DME)(3)][((Me3Si)(2)N)(2)U(mu-N)(mu-kappa(2):CN-CH2SiMe2NSiMe3)U(N(SiMe3)(2))(2)] (DME = 1,2-dimethoxyethane), 1, with 2 equiv of HNEt3BPh3 yielded the cationic U(IV)/U(IV) nitride complex, [{((Me3Si)(2)N)(2)U(THF)}(2)(mu-N)][BPh4] (THF = tetrahydrofuran), 3, by successive protonolysis of one N(SiMe3)(2) ligand and the uranium-methylene bond. Reduction of 3 with KC8 afforded a rare example of a U(III) nitride, namely, the U(III)/U(IV) complex, [{((Me3Si2N)(2)U(THF)}(2)(mu-N)], 4. Complex 4 is highly reactive and undergoes 1,2-addition of the C-H bond of the N(SiMe3)(2) ligand across the uranium-nitride moiety to give the U(III)/U(IV) inside cyclometalate complex, [{((Me3Si)(2)N)(2)(THF)U(mu-NH)(mu-kappa(2):C,N - CH2SiMe2NSiMe3)U(N(SiMe3)(2)))(THF)], 5. Complex 4 also reacts with toluene at -80 degrees C to yield an inverse sandwich imide complex arising from C-H bond activation of toluene, [{((Me3SO2N)(2)U(THF)}(2)(mu-N)]{((Me3SO2N)(3)U(mu-NH)U(N(SiMe3)(2))(C7H8)], 6. Complex 4 effects the heterolytic cleavage of the C-H of phenylacetylene to yield the imide acetylide [{((Me3Si)(2)N)(2)U(THF)[(2)(mu-N)][((Me3Si)(2)N)(2)U(eta(1)-CCPh)(mu(2)-NH)(mu(2)-eta(2): eta(1)-CCPh)U(N(SiMe3)(2))(2)], 7. Complex 4 also reacts with H-2 to produce an imide hydride U(III)/U(IV) complex, [{((Me3SO2N)(2)U(THF)}(2)(mu-NH)(mu-H)], 9. These data demonstrate that nitride complexes of U(III) are accessible with amide ligands and show the high reactivity of molecular U(III) nitrides in C-H bond activation.