Three ruthenium complexes Lambda-[cis-Ru((R,R)-Me-BPE)(2)(H)(2)] Lambda-R,R-Ru1H(2), Delta-[cis-Ru((S,S)-Me-DuPHOS)(2)-(H)(2)] Delta-S,S-Ru2H2, and Lambda-[cis-Ru((R,R)-Me-DuPHOS)(2)(H)(2)] Lambda-R,R-Ru2H(2) (1 = (Me-BPE)(2), 2 = (Me-DuPHOS)(2)) were characterized by multinuclear NMR and CD spectroscopy in solution and by X-ray crystallography. The chiral ligands allow the full control of stereochemistry and enable mechanistic studies not otherwise available. Oxidative addition of E H bonds (E = H, B, Si, C) was studied by steady state and laser flash photolysis in the presence of substrates. Steady state photolysis shows formation of single products with one stereoisomer. Solid state structures and circular dichroism spectra reveal a change in configuration at ruthenium for some Delta-S,S-Ru2H2/Lambda-R,R-Ru2H(2) photoproducts from Lambda to Delta (or vice versa) while the configuration for Lambda-R,R-Ru1H(2) products remains unchanged as Lambda. The X-ray structure of silyl hydride photoproducts suggests a residual H(1)center dot center dot center dot Si(1) interaction for Delta-[cis-Ru((R,R)-Me-DuPHOS)(2)(Et2SiF)(H)] and Delta-[cis-Ru((R,R)-Me-DuPHOS)(2)(PhSiH2)(H)] but not for their Ru(R,R-BPE)(2) analogues. Molecular structures were also determined for Lambda-[cis-Ru((R,R)-Me-BPE)(2)(Bpin)(H)], Lambda-[Ru((S,S)-Me-DuPHOS)(2)(eta(2)-C2H4)], Delta-[Ru((R,R)-Me-DuPHOS)(2)(eta(2)-C2H4)], and trans-[Ru((R,R)-me-DuPHOS)(2)(C6F5)(H)]. In situ laser photolysis in the presence of p-H-2 generates hyperpolarized NMR spectra because of magnetically inequivalent hydrides; these experiments and low temperature photolysis with D-2 reveal that the loss of hydride ligands is concerted. The reaction intermediates [Ru(DuPHOS)(2)] and [Ru(BPE)(2)] were detected by laser flash photolysis and have spectra consistent with approximate square-planar R(0) structures. The rates of their reactions with H-2, D-2, HBpin, and PhSiH3 were measured by transient kinetics. Rate constants are significantly faster for [Ru(BPE)(2)] than for [Ru(DuPHOS)(2)] and follow the substrate order H-2 > D-2 > PhSiH3 > HBpin.