A Three‐Membered Diazo‐Aluminum Heterocycle to Access an Al=C π Bonding Species

Abstract [1+2] cycloaddition between a cyclic (alkyl)(amino)aluminyl anion ( 3 ) and diaryldiazomethane affords an AlN 2 three‐membered ring species ( 4 ). Compound ( 4 ) is thermally unstable and spontaneously releases N 2 gas under the mild reaction condition to generate an ion‐separated species 5 . An X‐ray study shows that the anionic part of 5 bears a considerable short exocyclic Al−C bond, and computational studies involving molecular orbital and natural bond orbital analysis indicate the Al=C π bonding character. The Al=C moiety of 5 undergoes intramolecular C−H activation. Moreover, reaction of 5 with a diazo compound leads to the reduction and complete cleavage of the N=N double bond.