RuH2(DMPE)2 [DMPE = 1,2-bis(dimethylphosphino)ethane] was synthesized by reduction of trans-RuCl2(DMPE)2 with sodium/2-propanol. Protonation of RuH2(DMPE)2 with weak organic acids such as methanol, ethanol, and thiols affords the molecular hydrogen complex trans-[RuH(eta2-H-2)(DMPE)2]+, which has an eta2-bound H-2 ligand and a sigma-bound hydride ligand. T1 measurements and the observation of a large 1J(HD) coupling in the eta2-HD isotopomer ligand support the "nonclassical" structure. In the H-1 NMR spectrum of the trans-[RuH(eta2-HD)(DMPE)2]+ isotopomer, the proton-proton coupling (across the metal center) between sigma-H and H-1 in the eta2-HD was measured at 4.5 Hz. Between 220 and 300 K, the molecular hydrogen complex undergoes intermolecular exchange with the protonating reagent and all the ruthenium-bound hydrogens in the molecular hydrogen complex undergo intramolecular exchange. The weakly bound eta2-H-2 ligand is readily displaced by alkane- and arenethiols to give trans-monothiolate hydrides. With thiophenol, a second substitution occurs to give a dithiolate complex. Crystals of trans-Ru(SPh)2- (DMPE)2 are monoclinic, space group P2(1)/a, with a = 15.03 5(3) angstrom, b = 9.881(3) angstrom, c = 19.604(4) angstrom, beta = 97.51(2)degrees, Z = 4, and R = 0.029 [3348 reflections used with I > 2.5sigma(I)]. The structural analysis shows that Ru is coordinated by two bidentate phosphine and two monodentate benzenethiolate ligands in a trans arrangement.