Synthesis and Reactivity of Tricoordinate Organoberyllium Azides

A series of terminal mono‐ and disubstituted beryllium azides of the form [(CAAC)Be(N3)R] (R = CAACH, Dur; CAACH / CAAC = 1‐(2,6‐diisopropylphenyl)‐3,3,5,5‐tetramethylpyrrolidin‐2‐yl/idene, Dur = 2,3,5,6‐tetramethylphenyl) and [L2Be(N3)2] (L = CAACNH = 1‐(2,6‐diisopropylphenyl)‐3,3,5,5‐tetramethylpyrrolidin‐2‐imine, IiPrMe = 1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene), respectively, were synthesized and characterized by NMR spectroscopy and X‐ray crystallography. Thermolysis and photolysis products of these first examples of tricoordinate azidoberyllium complexes evidence extensive ligand scrambling and the formal insertion of nitrenes into the CAAC‒Be bond, generating cyclic alkyl(amino)imine (CAAI) ligands. Furthermore, the reaction with a small N‐heterocyclic carbene (NHC) leads to unexpected CAAC‐NHC ligand exchange, while the reaction with pentaphenylborole yields the first γ‐azide adduct of a borole, long postulated to be the first step in the synthesis of 1,2‐azaborinines from boroles and azides.