Photochemical Oxidative Addition of Germane and Diphenylgermane to Ruthenium Dihydride Complexes

Photochemical reactions of germane and diphenylgermane with Ru­(PP)2H2 (PP = R2PCH2CH2PR2 or DuPhos, R = Ph dppe, R = Et depe, R = Me dmpe) are reported. Reaction with GeH4 generates a mixture of cis and trans isomers of Ru­(PP)2(GeH3)H except for the DuPhos complex which yields the product only in the cis form. In situ laser photolysis (355 nm) demonstrates that the initial product is the cis isomer that undergoes thermal isomerization to the trans isomer. The complex cis-[Ru­(dppe)2(GeH3)­H] crystallizes selectively, allowing determination of its X-ray structure as a germyl hydride with a long Ru–H···Ge separation of 2.64(3) Å indicating that no residual interaction between the RuH and Ge is present. DFT calculations are also consistent with full oxidative addition. The structure of cis-[Ru­(DuPhos)2(GeH3)­H] reveals significant distortion from an octahedral geometry. The major species in the crystal (95%) exhibits a structure with a Ru–H···Ge distance of 2.42(5) Å suggesting negligible interaction between these centers. DFT calculations of the structure are consistent with the experimental determination. The reactions of Ru­(PP)2H2 with diphenylgermane yield cis-[Ru­(PP)2(GePh2H)­H] exclusively for PP = dmpe and depe, while the cis isomer is dominant in the case of dppe. A photochemical competition reaction between Ru­(dppe)2(H)2 and the two substrates Ph2SiH2 and Ph2GeH2 results in both Si–H and Ge–H oxidative addition activation with a kinetic preference (0.18:1) for the germyl hydride product. Thermal conversion of Ru­(dppe)2(SiPh2H)H to Ru­(dppe)2(GePh2H)H is observed on heating.