Metallaoxetanes and Carbenes from Diolates in High‐Valent Rhenium Oxo Chemistry: The Importance of the Coordination Number

ReV diolate complexes cleave to form either the ReVII trioxo complex or a rhenium carbene, depending on the coordination number of the original diolate complex (see picture). The carbene complexes, detected by using collision induced mass spectrometry, are the best experimental indication to date for intermediate “metallaoxetanes”, which would be the first-formed intermediate in [2+2] reactions of olefins with a d0 oxo complex. This sharp dichotomy in reactivity can be explained by a qualitative π-strain model.