Detection of the Tungsten–Carbene–Olefin Intermediates in Catalytic Metathesis Systems Containing High‐Valent Metal Centers

Abstract

The catalytic ring-opening polymerization of cycloheptene 2 proceeds through the rearrangement of 3 to give the corresponding metallacyclobutane. Compound 3, which is prepared in situ by addition of 2 to the carbone complex 1 and can be characterized by low-temperature 1H and 13C NMR spectroscopy, is therefore considered a key intermediate for these reactions that are also commercially important. Complexes of this type have up to now been postulated but not detected for catalytic olefin metatheses. R = CH2CMe3.