Synthesis and Electronic Features of M-N Bonding of N-Heterocyclic Imine Coordinated Alkali-Metal Amides [MN(SiMe3)2, M = Li, Na, K].

Abstract

N-Heterocyclic imine (NHI) ligands are attractive due to their strong electron-donating properties, and their applications in coordination chemistry continue to expand. In this study, we investigated the reactivity of MN(SiMe3)2 (M = Li, Na, K) toward (tBu2NHC)NH, and (Me2CAAC)NH [NHC = N-heterocyclic carbene, CAAC = cyclic (alkyl)(amino)carbene]. The basicity of MN(SiMe3)2 (M = Li, Na, K) was insufficient to deprotonate the N─H bond of these carbene-derived imines; instead, coordination complexes were formed. The lithium derivative was isolated with the general formula [{(carbene)NH}2LiN(SiMe3)2], whereas the sodium and potassium bis(trimethylsilyl)amide analogues crystallized as [{(carbene)NH}2{MN(SiMe3)2}2] (M = Na, K). The compounds were thoroughly characterized by multinuclear NMR spectroscopy and single-crystal x-ray diffraction. Furthermore, the x-ray quantum crystallographic (QCr) technique of Hirshfeld Atom Refinement (HAR) revealed hydrogen atom positions and electronic features of the M─N bonds.

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