Detection of diastereoisomers of metallacyclobutane intermediates in the metathesis polymerization of norbornene and its derivatives

Abstract

Addition of norbornene derivatives to racemic mixtures of chiral tungsten–carbene complexes is shown to lead to the formation of transoid diastereoisomeric tungstacyclobutanes that can be distinguished by 1H n.m.r. spectroscopy; cisoid structures, though formed, are too unstable to be observed.