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

Abstract

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 H2. Treatment of the previously reported U(IV)/U(IV) nitride complex [Na(DME)3][((Me3Si)2N)2U(μ-N)(μ-κ2:CN̵–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)2N)2U(THF)}2(μ-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, [{((Me3Si)2N)2U(THF)}2(μ-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) imide cyclometalate complex, [((Me3Si)2N)2(THF)U(μ-NH)(μ-κ2:C,N̵–CH2SiMe2NSiMe3)U(N(SiMe3)2))(THF)], 5. Complex 4 also reacts with toluene at −80 °C to yield an inverse sandwich imide complex arising from C–H bond activation of toluene, [{((Me3Si)2N)2U(THF)}2(μ-N)][{((Me3Si)2N)3U(μ-NH)U(N(SiMe3)2)}2(C7H8)], 6. Complex 4 effects the heterolytic cleavage of the C–H of phenylacetylene to yield the imide acetylide [{((Me3Si)2N)2U(THF)}2(μ-N)][((Me3Si)2N)2U(η1-CCPh)(μ2-NH)(μ2-η2:η1-CCPh)U(N(SiMe3)2)2], 7. Complex 4 also reacts with H2 to produce an imide hydride U(III)/U(IV) complex, [{((Me3Si)2N)2U(THF)}2(μ-NH)(μ-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.

Topics & Concepts