Hydrogenation of CO2, carbonyl and imine substrates catalyzed by IrH3((PNP)-P-Ph-P-H)] complex

A series of iridium and rhodium complexes M(COD)((PNP)-P-Ph-P-H)]Cl {M = Ir (1), Rh (2)}, MH2Cl((PNP)-P-Ph-P-H)] {M = Ir (3), Rh (4)} and IrH3((PNP)-P-Ph-P-H)] (6) supported by pincer ligand HeN(CH2CH2PPh2)(2) {(PNP)-P-Ph-P-H} have been synthesized and characterized. All complexes were isolated in good yields. The iridium trihydride complex IrH3((PNP)-P-Ph-P-H)] (6) was found to be an active catalyst for the hydrogenation of CO2 in 1 M aqueous KOH solution. It also acts as a catalyst for the base-free hydrogenation of carbonyl and imine substrates in MeOH. Under similar hydrogenation conditions, 2-cyclohexen-1-one undergoes solvent assisted tandem Michael addition-reduction mediated by bifunctional Lewis-acid-catalyst IrH3((PNP)-P-Ph-P-H)] in ROH (R = Me, Et) at room temperature. The complexes 1, 3, 4, and 6 were characterized by X-ray crystallography. Extensive hydrogen bonding interactions N-H center dot center dot center dot H-Ir (2.15 angstrom), N-H center dot center dot center dot center dot Cl (2.370 angstrom) were noted in the crystal structures of these complexes. (C) 2018 Elsevier B.V. All rights reserved

Impact of the Alkali Metal on the Structural and Dynamic Properties of the Anionic Pentahydride Ruthenium Complexes [M(THF) x ][RuH 5 (PCy 3 ) 2 ] (M = Li, Na, K)

International audienceA series of anionic ruthenium pentahydride complexes with the general formula [M(THF)x][RuH5(PCy3)2] (M = Li, Na, K) were synthesized. Their characterization by multinuclear NMR, IR, X-ray diffraction, and DFT techniques show that these complexes can adopt different structural features (monomer/dimer, cis/trans phosphines, hydride/dihydrogen ligands) depending on the countercation, the solvent, and/or the temperature. While the X-ray diffraction analyses offer snapshots of three out of five isomeric structures found by DFT, the solution and solid-state NMR analysis proved that these complexes exhibit a highly dynamic behavior. Rapid H–D exchange was found between Ru–H and D2, which was attributed to the presence of Ru–H·····M interactions in the absence of crown-ether

Combined B–H and Si–H Bond Activations at Ruthenium

The coordination of 2-mercaptobenzothiazolyl (mbz) and 2-mercaptopyridyl (mp) to a [Ru]–H precursor led to the isolation of two hydrido(dihydroborate) complexes [RuH(PCy3)2{κ3-H,H,S-(H)2BH(L)}] (L = mbz (1a), mp (1b)). Oxidative addition of secondary and tertiary silanes to 1a and 1b afforded the dihydrido ruthenium(IV) [RuH2(SiPh2R)(PCy3){κ3-H,H,S-(H)2BH(L)}] (R = H, L = mbz (2a), mp (2b); R = Me, L = mbz (2c)) featuring a coordinated borohydride moiety and a silyl ligand in weak interaction with the two hydride ligands of the ruthenium center. 1D and 2D NMR investigations at different temperatures as well as D2 reactivity, enabled to characterize exchange between every Si–H, Ru–H, and B–H hydride sites

Hydroxypyridine/pyridone interconversions within ruthenium complexes and their application in the catalytic hydrogenation of CO₂

Reaction of a new ligand 6-DiPPon (6-diisopropylphosphino-2-pyridone) with 0.5 equiv of [RuCl2(p-cymene)]2 resulted in the formation of a mixture of [RuCl2(p-cymene)(κ1-P-6-DiPPon)]2 (1) and [RuCl(p-cymene)(κ2-P,N-6-DiPPin)]Cl ([2]Cl) (where 6-DiPPin = 6-diisopropylphosphino-2-hydroxypyridine). The ratio between the two products can be controlled by the nature of the solvent. The similar reaction between 6-DiPPon and [RuCl2(p-cymene)]2 in the presence of AgOTf and Na[BArF24] (where BArF24 = [{3,5-(CF3)2C6H3}4B]−) resulted in the formation of the complexes [RuCl(p-cymene)(κ2-P,N-6-DiPPin)]OTf, ([2]OTf) and [RuCl(p-cymene)(κ2-P,N-6-DiPPin)]BArF24 ([2]BArF24), respectively. Reactions between complex [2]Cl, [2]OTf, or [2]BArF24 and a base (either DBU or NaOMe) resulted in the deprotonation of the hydroxyl functional group to form a novel neutral orange-colored dearomatized complex, 3. The identity of complex 3 was confirmed as [RuCl(p-cymene)(κ2-P,N-6-DiPPon*)], where 6-DiPPon* is the anionic species (6-diisopropylphosphino-2-oxo-pyridinide), which contains the deprotonated moiety. The new 6-DiPPon ligand and its corresponding air stable half-sandwich derivative ruthenium complexes 1, [2]OTf, [2]BArF24, and 3 were all isolated in good yields and fully characterized by spectroscopic and analytical methods. The interconversions between the neutral and anionic forms of the ligands 6-DiPPon, 6-DiPPin, and 6-DiPPon* offer the potential for novel secondary sphere interactions and proton shuttling reactivity. The consequences for this have been explored in the activation of H2 and the subsequent catalytic hydrogenations of CO2 into formate salts in the presence of a base.</p