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Reductions of M{N(SiMe3)2}3 (M = V, Cr, Fe): Terminal and Bridging Low-Valent First-Row Transition Metal Hydrido Complexes and “Metallo-Transamination”
journal contribution
posted on 2021-07-12, 11:36 authored by Cary R. Stennett, Clifton L. Wagner, James C. Fettinger, Petra Vasko, Philip P. PowerThe reaction of the vanadium(III)
tris(silylamide) V{N(SiMe3)2}3 with
LiAlH4 in diethyl
ether gives the highly unstable mixed-metal polyhydride [V(μ2-H)6[Al{N(SiMe3)2}2]3][Li(OEt2)3] (1),
which was structurally characterized. Alternatively, performing the
same reaction in the presence of 12-crown-4 affords a rare example
of a structurally verified vanadium terminal hydride complex, [VH{N(SiMe3)2}3][Li(12-crown-4)2] (2). The corresponding deuteride 2D was also prepared
using LiAlD4. In contrast, no hydride complexes were isolated
by reaction of M{N(SiMe3)2}3 (M =
Cr, Fe) with LiAlH4 and 12-crown-4. Instead, these reactions
afforded the anionic metal(II) complexes [M{N(SiMe3)2}3][Li(12-crown-4)2] (3, M = Cr; 4, M = Fe). The reaction of the iron(III)
tris(silylamide) Fe{N(SiMe3)2}3 with
lithium aluminum hydride without a crown ether gives the “hydrido
inverse crown” complex [Fe(μ2-H){N(SiMe3)2}2(μ2-Li)]2 (5), while treatment of the same trisamide with alane
trimethylamine complex gives the iron(II) polyhydride complex Fe(μ2-H)6[Al{N(SiMe3)2}2]2[Al{N(SiMe3)2}(NMe3)] (6). Complexes 2–6 were characterized by X-ray crystallography, as well as by infrared,
electronic, and 1H and 13C (complex 6) NMR spectroscopies. Complexes 1 and 6 are apparently formed by an unusual “metallo-transamination”
process.
