Reactivity of Pnictaalumenes Towards 1,3‐Dipole Molecules

Abstract

Abstract Alkynes undergo 1,3‐dipolar cyclization reactions with organic azides giving 1,2,3‐triazoles. Pnictaalumenes RPn═AlRˈ are the isoelectronic congeners of alkynes, hence a similar reactivity toward 1,3‐dipole molecules is expected. Herein, we report the reactions of Dipp TerPn═AlCp* ( Dipp Ter  =  2,6‐(2,6‐ i Pr 2 C 6 H 3 )‐C 6 H 3 , Cp*  =  [Me 5 C 5 ], Pn  =  P, As) toward aryl azides. Instead of the anticipated phosphaaluminatriazole products from a [3+2] cyclization, the formation of four‐membered AlN 2 Pn ring systems of the general form Dipp TerPn( μ ‐NR) 2 AlCp* was observed. Depending on the steric profile of the azide, different outcomes were observed: a) N α insertion into the Pn═Al bond accompanied by twofold N 2 elimination, b) N γ insertion under preservation of the N 3 motif, or c) mixed N a /N γ products. The bonding situation is complex and best described as Al(III) complexes with NPnN‐amino‐amide‐type ligands. A twofold insertion also occurs with the isovalent electronic diazoalkane Me 3 Si(H)C═N 2 , yielding imine‐substituted AlN 2 Pn derivatives. In the case of its P‐congener, two thermal rearrangements were observed, which first result in a AlN 3 P ring species with a terminal Al─CN unit, followed by a second slower rearrangement to an aluminate cyanido complex with an unusual NNN pincer‐type ligand framework. The current study contrasts well‐established [3+2] cyclization reactions between alkynes and 1,3‐dipoles and provides access to unprecedented ligand motifs.