Triply-bridged diruthenium(II) 1,4-bis(diphenylphosphino)butane (dppb) and (R)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (binap) complexes, including structural characterisation of [(dppb) ClRu(μ-D2O)-(μ-Cl)2RuCl(dppb)], [(η2-H2) (dppb)Ru(μ-Cl)3RuCl(dppb)] and the [(dppb)ClRu(μ-Cl)3RuCl(dppb)]− anion

Catalytic hydrogenation of carboxylic acids using low-valent and high-valent metal complexes

Carboxylic acids are ubiquitous in bio-renewable and petrochemical sources of carbon.

Cationic mononuclear ruthenium carboxylates as catalyst prototypes for self-induced hydrogenation of carboxylic acids

Carboxylic acids are ubiquitous in bio-renewable and petrochemical sources of carbon. Hydrogenation of carboxylic acids to yield alcohols produces water as the only byproduct, and thus represents a possible next generation, sustainable method for the production of these alternative energy carriers/platform chemicals on a large scale. Reported herein are molecular insights into cationic mononuclear ruthenium carboxylates ([Ru(OCOR)]⁺) as prototypical catalysts for the hydrogenation of carboxylic acids. The substrate-derived coordinated carboxylate was found to function initially as a proton acceptor for the heterolytic cleavage of dihydrogen, and subsequently also as an acceptor for the hydride from [Ru–H]⁺, which was generated in the first step (self-induced catalysis). The hydrogenation proceeded selectively and at high levels of functional group tolerance, a feature that is challenging to achieve with existing heterogeneous/homogeneous catalyst systems. These fundamental insights are expected to significantly benefit the future development of metal carboxylate-catalysed hydrogenation processes of bio-renewable resources.

Many structurally diverse carboxylic acids are available from renewable and petrochemical sources. Here, the authors report a method to reduce carboxylic acids to alcohols using hydrogen, with high selectivity, wherein the carboxylates form active and hydrogen-accepting parts of the catalyst system.

Ruthenium(III) complexes containing bi- and tridentate phosphorus−nitrogen ligands

Air-stable RuIII complexes containing a bidentate aminophosphine ligand (PN) of the type mer-RuCl3(PN)(PR3) are made from the precursors RuCl3(PR3)2(DMA)·DMA (PN = o-diphenylphosphino-N,N′-dimethylaniline (P−N) and (R)-N,N′-dimethyl-1-[o-diphenylphosphinophenyl]ethylamine ((R)-AMPHOS); R = Ph, p-tolyl; DMA = N,N′-dimethylacetamide). With the tridentate bis[o-(N,N′-dimethylamino)phenyl]phenylphosphine (BNP), the product is mer-RuCl3(BNP) (3), while tris[o-(N,N′-dimethylaminophenyl)phosphine (TNP) is unreactive toward the precursor. Crystal structures of mer-RuCl3(PN)(PPh3), where PN is P−N (2a), (R)-AMPHOS (4a), and 3·CHCl3 are reported as well as those of (R)-AMPHOS, BNP, and TNP. The RuIII−aminophosphine complexes are the first monomeric RuIII species to be formed via the useful, easily synthesized, air-stable RuIII precursors RuCl3(PR3)2(DMA)·DMA (1a and 1b); complex 2a is formed also via reaction of HCl with trans-RuCl2(P−N)(PPh3). A crystal structure of mer,cis-RuCl3(DMA)2(PPh3)·DMA (1c), a side-product from the synthesis of the RuIII precursor, is also presented and is the first-reported complex of DMA with RuIII. Preliminary data show that the RuIII−aminophosphine complexes in DMA (a proton-accepting solvent) are reduced by H2 to RuII species that can react further to form an η2-H2 adduct and then a RuII-hydridochloro species.

Ruthenium(II) thiol and H2S complexes: synthesis, characterization, and thermodynamic properties

The known, green, five-coordinate species trans-RuCl(2)(P-N)(PPh(3)) react with R'SH thiols to give yellow cis-RuCl(2)(P-N)(PPh(3))(R'SH) products (P-N = o-diphenylphosphino-N,N'-dimethylaniline; R' = alkyl). The MeSH and EtSH compounds are structurally characterized, with the former being the first reported for a transition metal-MeSH complex, while the thiol complexes with R' = (n)Pr, (i)Pr, (n)Pn (pentyl), (n)Hx (hexyl), and Bn (benzyl) are synthesized in situ. Other trans-RuX(2)(P-N)(PR(3)) complexes (X = Br, I; R = Ph, p-tolyl) are synthesized, and their H(2)S adducts, of a type reported earlier by our group, are also prepared. Thermodynamic data are presented for the reversible formation of the MeSH and EtSH complexes and the H(2)S analogues. The Ru(II)Cl(2)(P-N)(PPh(3)) complex in solution decomposes under O(2) to form [Ru(III)Cl(P-N)](2)(μ-O)(μ-Cl)(2).