The Ru-PR3 bonds of 1-2(a-b)-PC, Ru=CHPh 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 Ru-PR3 bond is driven by charge transfer, while the RCB by polarization effects. Furthermore, the pi(C-ipso)-pi*(Ru=C) 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 (E-NLW). 2 presented a lower Delta E-NLW (Inactive. Active) than 1a-b, which confirms that the delocalization effects are related to a low carbene rotameric energy. (C) 2014 Elsevier B.V. All rights reserved.