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The four-coordinate compound (tBu2PCH2SiMe2)2NRuCH3 undergoes rapid double H-C(sp3) activation at -78 degrees C to generate a "hydrido-carbene" complex. DFT calculations suggest that the origin of the low barrier to methane elimination is an alpha-agostic interaction in the low-lying singlet state of the highly unsaturated (PNP)RuMe. The hydrido-carbene complex can be viewed as a "masked" resting state of the four-coordinate cyclometalated alkyl complex, (tBu2PCH2SiMe2)N(Me2SiCH2P(tBu)(C(CH3)2CH2)Ru, where hydride migration from metal to carbon occurs before any subsequent reactivity.
Ingleson et al. (Thu,) studied this question.