The synthesis of the new phosphinodi(benzylsilane) compound PhP{(O-C6H4CH2)SiMe2H}(2) (1) is :achieved in a one-pot reaction from the corresponding phenylbis(o-tolylphosphine). Compound 1.acts as a pincer type ligand capable of adopting different coordination modes at Ru through different.extents. of Si-H bond 'activation as demonstrated by a combination of X-ray diffraction analysis, density functional theory calculations, and multinuclear NMR Spectroscopy. Reaction of 1 with RuH2(H-2)(2)Cy-3)(2) (2) yields quantitatively [RuH2{eta(2)-(HSiMe2)-CH2-o- C6H4](2)PPh}(PCy3)] (3), a complex.Stabilized by two rare high order epsilon-agostic Si-H bonds and involved in terminal hydride/eta(2) -Si-H exchange processes. A small free energy of reaction (Delta(r)G(298) = +16.9 kJ mol(-1)) was computed for dihydrogen loss from 3 with concomitant formation of the 16-electron species [RuH{[eta(2)-(HSiMe2)-CH2-o-C6H4]PPh[CH2-o-C6H4SiMe2])(PCy3)] (4). Complex 4 features an unprecedented Si-29 NMR decoalescence process. The dehydrogenation process is frilly reversible under standard conditions (1 bar, 298 K).