Strong Evidence for an Unprecedented Borderline Case of Dissociation and Cycloaddition in Open‐Shell 1,3‐Dipole Chemistry: Transient Nitrilium Phosphane‐Ylide Complex Radical Cations

Abstract

AbstractThe reaction of 3‐ferrocenyl‐substituted 2H‐azaphosphirene complexes 1a–c in the presence of substoichiometric amounts of ferrocenium hexafluorophosphate yields 3,5‐diferrocenyl‐substituted 2H‐1,4,2‐diazaphosphole complexes 3a–c and difluoro(organo)phosphane complexes 4a–c. The reaction of 1a,c and [FcH]PF6 with cyanoferrocene yields 3a,c in a straightforward way. The molecular structures of 3a,c were unambiguously identified by multinuclear NMR spectroscopic experiments, mass spectrometry, and single‐crystal X‐ray diffraction studies. DFT calculations on model complexes 1d–m and 3d–m reveal a close similarity of Mo and W complexes (vs. Cr) and a strong influence of the ferrocenyl substituent on the geometry, spin, and charge distribution of reactive intermediates and the reaction course. Strong support for the assumption of a dissociation–cycloaddition reaction sequence leading to 3 and thus a surprising “cannibalistic” reaction was obtained.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)