Photochemical oxidative addition of germane and diphenylgermane to ruthenium dihydride complexes

Photochemical reactions of germane and diphenylgermane with Ru(PP) 2 H 2 (PP = R 2 PCH 2 CH 2 PR 2 or DuPhos, R = Ph dppe, R = Et depe, R = Me dmpe) are reported. Reaction with GeH 4 generates a mixture of cis and trans isomers of Ru(PP) 2 (GeH 3 )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 (GeH 3 )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 (GeH 3 )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) 2 H 2 with diphenylgermane yield cis-[Ru(PP) 2 (GePh 2 H)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 Ph 2 SiH 2 and Ph 2 GeH 2 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 (SiPh 2 H)H to Ru(dppe) 2 (GePh 2 H)H is observed on heating

Mapping Out the Role of σ-Silane Complexes in the Ruthenium-Catalyzed Hydrosilylation of Nitriles

A combined synthetic, mechanistic, and computational study is reported, which provides unique insight into the role of σ-silane complexes in the catalytic hydrosilylation of nitriles. A novel, highly efficient, highly active, and regioselective catalytic monohydrosilylation of aromatic nitriles with secondary silanes using a ruthenium dihydrogen catalyst is reported along with a novel mechanism for hydrosilylation of nitriles. Investigations into the mechanism of this transformation have revealed the influence of σ-Si-H complexes in fine-tuning the selectivity of this hydrosilylation reaction. Displacement of the dihydrogen ligand on the ruthenium precatalyst, ruthenium bis-(dihydrogen) complex [RuH2(η2-H2)2(PCy3)2], 1, by diphenylsilane leads to the formation of new ruthenium σ-Si-H complexes, [RuH2(η2-H2)(η2-HSiHPh2)(PCy3)2], 2, and [RuH2(η3-H2SiPh2)(PCy3)2], 3. Complex 3 reacts readily with benzonitrile leading to hydrosilylation of the nitrile and coordination of the silylimine formed to the ruthenium as a σ-H-Si-N-silylimine complex, [RuH2(η2-HSiPh2NCHPh)(PCy3)2] (4). This systematic investigation of this reactivity led to the discovery of the first direct evidence of an N-silylimine-coordinated ruthenium complex and its involvement in a catalytic hydrosilylation reaction. This led to the discovery of a catalytic protocol for the efficient and selective coupling of secondary silanes with a range of nitriles using 1 as the catalyst. It is proposed that complexes 3 and 4 are key intermediates on the catalytic reaction coordinate, which leads to hydrosilylation of the nitrile. This is supported by DFT calculations along with the observation that 3 and 4 are catalytically active. The Si-N bond formation was found to proceed via direct attack of the nitrile at the silicon atom in 3. Through carefully chosen structural studies and tests of the new ruthenium complexes, along with DFT calculations, the mechanism of the catalytic hydrosilylation of nitriles has been successfully explained

HLA-DQA1*05 carriage associated with development of anti-drug antibodies to infliximab and adalimumab in patients with Crohn's Disease

Anti-tumor necrosis factor (anti-TNF) therapies are the most widely used biologic drugs for treating immune-mediated diseases, but repeated administration can induce the formation of anti-drug antibodies. The ability to identify patients at increased risk for development of anti-drug antibodies would facilitate selection of therapy and use of preventative strategies.This article is freely available via Open Access. Click on Publisher URL to access the full-text

International genome-wide meta-analysis identifies new primary biliary cirrhosis risk loci and targetable pathogenic pathways.

Primary biliary cirrhosis (PBC) is a classical autoimmune liver disease for which effective immunomodulatory therapy is lacking. Here we perform meta-analyses of discovery data sets from genome-wide association studies of European subjects (n=2,764 cases and 10,475 controls) followed by validation genotyping in an independent cohort (n=3,716 cases and 4,261 controls). We discover and validate six previously unknown risk loci for PBC (Pcombined<5 × 10(-8)) and used pathway analysis to identify JAK-STAT/IL12/IL27 signalling and cytokine-cytokine pathways, for which relevant therapies exist

Ruthenium silane and germane complexes (synthesis, electrochemical and catalytic studies)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Enhancing hydrogen storage properties of the Mg/MgH2 system by the addition of bis(tricyclohexylphosphine)nickel(II) dichloride

SSCI-VIDE+ATARI+BGL:AAU:GPOInternational audienceHydrogen storag

Addition of dihydrogen Ruthenium complexes to MgH2: a way to improve the decomposition kinetics?

SSCI-VIDE+ATARI+BGL:AAU:GPOInternational audienceINTRODUCTIONBecause of the increasing worldwide energy demand, new technologies to produce power with less greenhouse gas emissions are needed. Hydrogen has been identified as a potential clean and renewable energy carrier for the future as it can be easily and efficiently converted in electricity1. However a reliable and secure way of storage is essential for the expansion of its utilization2. Materials that can reversibly absorb large amount of hydrogen by means of chemical reactions are the most suitable to reach industrial applications. Among them, metal hydrides and especially magnesium hydride showed great potential. Nevertheless, the high thermodynamic stability of the system and slow hydrogen absorption/desorption kinetics limit its practical usage3. Important advances have been observed by using nano-structured magnesium hydride with additives to accelerate the dehydrogenation process. But the progresses made up to date are not enough to meet the requirements for low temperature fuel cell applications4.EXPERIMENTAL/THEORETICAL STUDYIn the present work, the use of dihydrogen ruthenium complexes for improving the absorption/desorption properties of Mg/MgH2 system is for the first time reported. Dihydrogen ruthenium complexes in which one, two or more dihydrogen molecules are coordinated to a transition metal center without H-H bond breaking represent an ideal class in terms of binding strength midway between metal hydrides and physisorption5, 6.Two different ways of preparing the MgH2 and Ru complex mixtures have been tested: ball-milling and solvent impregnation. Microstructure, phase composition and morphology of commercial, nanostructured and doped MgH2 powders were fully characterized by XRD and SEM-TEM. Temperature programmed techniques, TPD, TGA and DSC, were used to investigate the hydrogen desorption kinetics and a PCT device allowed to build the absorption/desorption isotherms and study the reversibility of the process.RESULTS AND DISCUSSIONThe impact of doping MgH2 with dihydrogen ruthenium complexes is presented in figure 1. MgH2 was doped by ball milling with 5wt% of a ruthenium complex able to coordinate two dihydrogen molecules. The hydrogen desorption was followed by TPD analysis. The figure shows that the complex addition has a significant impact on the dehydrogenation properties of MgH2. It reduces the desorption temperature and allows a better homogeneity in comparison with nano-structured MgH2.Fig. 1: TPD analysis at 2°C/min of (1) MgH2 doped with 5wt% of complex (2) milled MgH2 (3) commercial MgH2TGA, DSC and PCT analysis confirmed that using a dihydrogen ruthenium complex as doping agent has a positive impact on the hydrogen storage properties of MgH2. TEM analysis showed that a protective layer of complex is formed at the surface of MgH2. Its role may therefore be to homogenously disperse the ruthenium in the mixtures and to prevent the sintering of the MgH2 particles after milling, allowing faster absorption/desorption kinetics.CONCLUSIONThe efficiency of using dihydrogen ruthenium complexes as doping agent to MgH2 will be discussed. The concept that increasing the number of dihydrogen ligands for better hydrogen release kinetics will be demonstrated in this work. Important kinetic improvements are expected by adding metallic nanoparticles (Ni, Ti…) to the “MgH2 + complex” samples. REFERENCES1. K. L. Lim, Chem. Eng. Technol. 33, 213-226 (2010)2. S. Niaz, Renew. Sust. Energ. Rev. 50, 457-469 (2015)3. Z.X. Guo, J. Eur. Ceram. Soc. 28, 1467-1473 (2008)4. H. Yu, Int. J. Hydrogen Energ. 39, 11633-11641 (2014)5. M. Grellier, Chem. Commun. 48, 34-42 (2012)6. M. Grellier, Inorg. Chem. 52, 7329-7337 (2013)ACKNOWLEDGMENTSThe authors acknowledge the ANR (French National Research Agency) for the financial support (grant 3H2/2016)