05/2015

We analyzed electronic factors affecting the mechanism of metal-catalyzed C–H bond alkylation by diazocarbene precursors. The analyses showed that e efficient metal-catalyzed alkylation of C–H bond by diazocarbenes requires a fine balance (i) of the triplet and singlet electronic states of carbenes: availability of singlet and triplet states is crucial for electrophilic and nucleophilic character of carbene fragment of metallocarbenes; and (ii) in the metal–carbene bond strength: a strong metal–carbene bond is required for facile diazocarbene decomposition, while weak metal–carbene interaction is beneficiary for the metallo-carbene reaction with various substrates.

The aforementioned delicate balance is predicted to be achieved by utilizing a combination of (i) transition metals with smaller energy gap between their s1dn−1 and s0dn electron configurations, and triplet carbenes with an energetically close singlet electronic state or/and (ii) transition metals with a ground s0dn electron configuration and carbenes with a singlet ground electronic state.