15 research outputs found
Synthesis of Allyl and Alkyl Vinyl Ethers Using an in Situ Prepared Air-Stable Palladium Catalyst. Efficient Transfer Vinylation of Primary, Secondary, and Tertiary Alcohols
Synthesis, Structure, and Properties of the Stable and Highly Acidic Dihydrogen Complex trans
Comparison of the Catalytic Activity of [(η<sup>5</sup>‑C<sub>5</sub>H<sub>5</sub>)Ru(2,2′-bipyridine)(L)]OTf versus [(η<sup>5</sup>‑C<sub>5</sub>H<sub>5</sub>)Ru(6,6′-diamino-2,2′-bipyridine)(L)]OTf (L = labile ligand) in the Hydrogenation of Cyclohexanone. Evidence for the Presence of a Metal–Ligand Bifunctional Mechanism under Acidic Conditions
The
two title complexes as well as the dimeric complex [RuÂ(II)Â(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)Â(6,6′-diamino-2,2′-bipyridine)]<sub>2</sub>(OTf)<sub>2</sub> have been synthesized and characterized
by NMR and single-crystal X-ray crystallography. The direct structural
comparison of the 2,2′-bipyridine and 6,6′-diamino-2,2′-bipyridine
complexes suggests that the electronic and steric environments of
the ruthenium centers in both complexes are essentially equivalent,
providing for a unique opportunity to probe the influence of the noncoordinated
amine substituent on the relative reactivity and catalytic activity
of the complexes. Opposite to what would be anticipated on the basis
of steric effects, the bulkier amine-substituted ligand results in
a catalyst showing substantially higher activity in the hydrogenation
of cyclohexanone in acidic medium, which is attributed to the operation
of a metal–ligand bifunctional hydrogenation mechanism mediated
by the amine substituents in their protonated form acting as proton
shuttles
Bioenergy II: Group 8 Metal Complexes as Homogeneous Ionic Hydrogenation and Hydrogenolysis Catalysts for the Deoxygenation of Biomass to Petrochemicals - Opportunities, Challenges, Strategies and the Story so Far
Ruthenium-8-quinolinethiolate-phenylterpyridine versus ruthenium-bipyridine-phenyl-terpyridine complexes as homogeneous water and high temperature stable hydrogenation catalysts for biomass-derived substrates
Hydrodeoxygenation of 2,5-Hexanedione and 2,5-Dimethylfuran by Water‑, Air‑, and Acid-Stable Homogeneous Ruthenium and Iridium Catalysts
The
complexes [(4′-Ph-terpy)ÂRuÂ(H<sub>2</sub>O)<sub>3</sub>]Â(OTf)<sub>2</sub> and [(4′-Ph-terpy)ÂIrÂ(OTf)<sub>3</sub>]
have been evaluated as catalysts for the conversion of 2,5-hexanedione
and 2,5-dimethylfuran to hydrodeoxygenated products in aqueous acidic
medium at elevated temperature (150–225 °C) under hydrogen
gas (5.5 MPa). These two substrates form part of a value chain leading
from C<sub>6</sub> sugars to 2,5-hexanediol, 2,5-dimethyltetrahydrofuran,
and hexane, which can be generated by the homogeneously acting ruthenium
catalyst in up to 69%, 80%, and 10% yield, respectively, while at <i>T</i> > 175 °C the iridium system decomposes to a highly
active but heterogeneously acting coating in the reactor defeating
the premise of a homogeneous catalyst system. The deactivation and
decomposition pathway of both catalysts leads to the formation of
a series of isostructural complexes [MÂ(4′-Ph-terpy)<sub>2</sub>]<sup><i>n</i>+</sup> (M = Fe, Ni, Ru, Ir; <i>n</i> = 2, 3) characterized by ESI-MS and single crystal X-ray crystallography,
in which the source of the Fe and Ni is the 316SS reactor body
Ruthenium triphos complexes [Ru(X(CH2PPh2)3-κ3-P)(NCCH3)3](OTf)2; X = H3C-C, N) as catalysts for the conversion of furfuryl acetate to 1,4-pentanediol and cyclopentanol in aqueous medium
The ruthenium complexes [Ru(H3CC(CH2PPh2)3-κ3-P)(NCCH3)3](OTf)2 (1, (H3CC(CH2PPh2)3 = triphos) and [Ru(N(CH2PPh2)3-κ3-P)(NCCH3)3](OTf)2 (2, N(CH2PPh2)3 = N-triphos) have been evaluated as homogeneous ionic hydrogenation catalysts for the catalytic hydrodeoxygenation of furfuryl alcohol and furfuryl acetate to 1,4-pentanediol and cyclopentanol in aqueous media reaction mixtures. For furfuryl alcohol, only marginal yields of 1,4-pentanediol could be achieved with mass balance deficiencies due to humin formation ranging from 67% to 90%. Attempts to improve the catalytic activity of 2 by enhancing its water solubility by nitrogen protonation and (or) methylation failed. Employing the less self-reactive furfuryl acetate as the substrate substantially diminishes humin formation, yielding up to 43% of 1,4-pentanediol and 19% of cyclopentanol (via Piancatelli rearrangement) with 1 and up to 33% of 1,4-pentanediol and 5% of cyclopentanol with 2. A design of experiments study was used to determine and compare the yield responses of the multiple parallel reaction channels with 1,4-pentanediol, cyclopentanol, and humins as a function of reaction temperature, time, catalyst load, and substrate concentration. This explores the correlations between these parameters and their impact on the reaction outcome and suggests an extremely complex overall reaction cascade of interdependent pathways of both acid- and metal-catalyzed steps with some significant differences emerging between the two catalysts.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author