Stepwise Acetylene Insertion and Ammonia Activation at a Digallene and Diindene

Abstract Sequential [2 + 2] cycloaddition reactions between acetylene and the digallene and diindene compounds (ETer) 2 (E = Ga, In; Ter = 2,6‐Dipp 2 ‐C 6 H 3 ; Dipp = 2,6‐diisopropylphenyl) are described. Careful control of the reaction conditions leads to selective formation of four‐ and six‐membered rings with 2π E 2 C 2 and 4π E 2 C 4 cores, respectively. A structural analysis of the heterocycles by single crystal X‐ray diffraction suggests limited electronic delocalization within the rings, which is borne out in their reactivity. For example, the six‐membered cyclohexadiene analogues exhibit Lewis‐acidic behavior and can form stable, isolable adducts with ammonia. Upon heating, these adducts transform into the corresponding bimetallic triel amides with concomitant generation of ethene.