The S/OH bridged dinuclear Ru−Ge complex cation, [Dmp(Dep)Ge(μ-S)(μ-OH)Ru(PR3)](BArF4) (3), which was synthesized quantitatively by the protonation of Dmp(Dep)Ge(μ-S)(μ-O)Ru(PR3) (1) with H(OEt2)2BArF4 (ArF = 3,5-(CF3)2C6H3), was found to promote facile and reversible H2 activation leading to H2O and [Dmp(Dep)Ge(μ-S)(μ-H)Ru(PR3)](BArF4) (4) under mild conditions. The μ-hydride of 4 exhibits protonic behavior, and the acidity of the μ-hydride is sufficiently high to transform 1 into 3. Thus, when a C6D6 solution of 1 with a catalytic amount of H(OEt2)2BArF4 (1 mol %) was heated to 70 °C for 24 h under an H2 atmosphere, [Dmp(Dep)Ge(μ-S)Ru(PR3)] (5) and H2O were formed. The molecular structures of 4 and 5 were determined by X-ray analysis. In the catalytic conversion of 1 to 5, H2 is consumed formally as two protons generating H2O, and two electrons which are stored in 5 as the Ge−Ru bond or as Ru d-electrons. Activation of H2 using the Ge−Ru complexes provides an intriguing functional model of hydrogenases, where the μ-O complex 1, the μ-OH complex 3, and the μ-H complex 4 may respectively correspond to the Ni-SU, the Ni-SIr, and the Ni-SIa states of [NiFe] hydrogenase.