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 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.