Initiation stage of alkene metathesis: Insights from natural bond orbital and charge decomposition analyses

The RuPR3 bonds of 1–2(a-b)-PC, RuCHPh bonds of 1a-b, 2-Inact/Act and 1a-b, 2-RCB were analyzed by charge decomposition (CDA) and natural bond orbital (NBO). We have found that the dissociation step of the RuPR3 bond is driven by charge transfer, while the RCB by polarization effects. Furthermore, the π(Cipso)–π*(RuC) interaction was associated with delocalization effects in the benzylidene ring. Likewise, the nature of the rotameric changes in the carbene was studied through the resonance stabilization energy (ENLW). 2 presented a lower ΔENLW (Inactive → Active) than 1a-b, which confirms that the delocalization effects are related to a low carbene rotameric energy.