PUB - Publikationen an der Universität Bielefeld

The reaction of the oxygen-bridged frustrated Lewis pairs (FLPs) tBu2P-O-Si(C2F5)3 (1) and tBu2P-O-AlBis2 (2) with azoben-zene, promoted by UV irradiation, led to a selective complexation of the cis-isomer. The addition product of 2 is stable, while the adduct of 1 isomerizes in solution in an ortho-benzidine-like [3,3]-rearrange-ment by cleavage of the N-N bond, saturation of the nitrogen atoms with hydrogen and formation of a new bond between two phenyl ortho-carbon atoms. Similar rearrangements take place with different para-substituted azobenzenes (R = Me, OMe, Cl) and di(2-naphthyl)-diazene, while ortho-methylated azo compounds do not form adducts with 1. All adducts were characterized by multinuclear NMR spectro-scopy and elemental analyses and the mechanism of the rearrange-ment was explored by quantum-chemical calculations. © 2023 Wiley-VCH GmbH.