Heterolytic activation of dihydrogen molecule by hydroxo-/sulfido-bridged ruthenium-germanium dinuclear complex. Theoretical insights.

Heterolytic activation of dihydrogen molecule (H2) by hydroxo-/sulfido-bridged ruthenium–germanium dinuclear complex [Dmp(Dep)Ge(μ-S)(μ-OH)Ru(PPh3)]+ (1) (Dmp = 2,6-dimesitylphenyl, Dep = 2,6-diethylphenyl) is theoretically investigated with the ONIOM(DFT:MM) method. H2 approaches 1 to afford an intermediate [Dmp(Dep)(HO)Ge(μ-S)Ru(PPh3)]+-(H2) (2). In 2, the Ru–OH coordinate bond is broken but H2 does not yet coordinate with the Ru center. Then, the H2 further approaches the Ru center through a transition state TS2–3 to afford a dihydrogen σ-complex [Dmp(Dep)(HO)Ge(μ-S)Ru(η2-H2)(PPh3)]+ (3). Starting from 3, the H–H σ-bond is cleaved by the Ru and Ge–OH moieties to form [Dmp(Dep)(H2O)Ge(μ-S)Ru(H)(PPh3)]+ (4). In 4, hydride and H2O coordinate with the Ru and Ge centers, respectively. Electron population changes clearly indicate that this H–H σ-bond cleavage occurs in a heterolytic manner like H2 activation by hydrogenase. Finally, the H2O dissociates from the Ge center to afford [Dmp(Dep)Ge(μ-S)Ru(H)(PPh3)...