Assembly of metallo-macrocycles through reductive C–C coupling of alkylnitriles by an Mg–Mg-bonded compound

Abstract

Low-valent metal complexes have attracted much research interest owing to their novel reactivities toward small molecules. Herein the reactivity of the α-diimine-ligated, Mg–Mg-bonded compound [K(THF)₃]₂[LMg–MgL] (1, L = [(2,6-iPr₂C₆H₃)NC(Me)]₂²⁻) with aliphatic nitriles has been studied. Complex 1 readily activates n-alkylnitriles (RCN; R = propyl, butyl, and pentyl) to afford the unique trinuclear magnesium metallo-macrocyclic complexes, [LMg(μ-{(NC–C(R)C(CH₂R)–NH})]₃[K₃(Solv)₆] (2–4: R = –(CH₂)_nCH₃, n = 2, 3, or 4; Solv = THF/DME), through a reductive deprotonation of the α-H of one nitrile molecule and C–C coupling between this α-carbon and the cyanide (CN) group of another nitrile, followed by a 1,3-H shift. The results demonstrate the possibility of assembling supramolecular architectures based on the α-diimine [LMg] fragment through small molecule activation.