1,720,997 research outputs found
Ruthenium and osmium complexes containing 2-(aminomethyl)pyridine (Ampy)-based ligands in catalysis
No full textThe pivotal role of the counterion in gold catalyzed hydration and alkoxylation of alkynes
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Chiral and non-Chiral [OsX2(diphosphane)(diamine)] (X = Cl, OCH2CF3) Complexes for Fast Hydrogenation of Carbonyl Compounds
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[Re2I2(CO)6(Se7)], a coordination compound with a ring-shaped polyselenium ligand: structure in solution and in the solid state
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Bulky Diphosphine Acetate Ruthenium Complexes: Synthesis and Catalytic Activity in Ketone Transfer Hydrogenation and Alkyne Dimerization
No full textSeveral mononuclear ruthenium complexes containing bulky diphosphines have been easily prepared from acetate ruthenium precursors. The cyclohexyl complex [Ru(η2-OAc)2(DCyPF)] (1-cy; DCyPF = 1,1′-bis(dicyclohexylphosphino)ferrocene) is synthesized from [Ru(η2-OAc)2(PPh3)2] and DCyPF in toluene at reflux, whereas the ethylenediamine (en) derivatives trans-[Ru(η1-OAc)2(PP)(en)] (PP = 1,1′-bis(diisopropylphosphino)ferrocene (DiPPF) (2), DCyPF (3)) have been obtained in a one-pot reaction from [Ru(η2-OAc)2(PPh3)2], PP, and en in n-heptane. Treatment of the isopropylphosphine complex [Ru(η2-OAc)2(DiPPF)] (1-ip) with 2-(aminomethyl)pyridine (ampy) in methanol affords the isolation of a mixture of the cationic [Ru(η2-OAc)(DiPPF)(ampy)]OAc (5a) and cis-[Ru(η1-OAc)2(DiPPF)(ampy)] (5b) (4/1 molar ratio), via trans-[Ru(η1-OAc)2(DiPPF)(ampy)] (4) characterized at low temperature. The analogous cyclohexyl compound trans-[Ru(η1-OAc)2(DCyPF)(ampy)] (6), synthesized from [Ru(η2-OAc)2(PPh3)2], DCyPF and ampy in heptane, slowly converts into [Ru(η2-OAc)(DCyPF)(ampy)]OAc (7) at RT. The monocarbonyl derivatives [Ru(η1-OAc)(η2-OAc)(PP)(CO)] (PP = 1,3-bis(cyclohexylphosphino)propane (DCyPP) (8), (R)-1-[(S)-2-(dicyclohexylphosphino)ferrocenyl]ethyldicyclohexylphosphine (Josiphoscy) (9)) are obtained from [Ru(ηsu1-OAc)(η2-OAc)(PPh3) 2(CO)] and the suitable diphosphine. Treatment of [Ru(η1-OAc)(η2-OAc)(DiPPF)(CO)] (10) with phenylacetylene and in the presence of pyridine leads to the alkynyl complex [Ru(η2-OAc)(CCPh)(DiPPF)(CO)] (11), characterized by X-ray diffraction analysis. Protonation of 10 with 2 equiv of TFA at RT gives [Ru(η1-OCOCF3)(η2-OCOCF3)(DiPPF)(CO)] (12). The dicarbonyl trans,cis-[Ru(η1-OAc)2(DiPPF)(CO)2] (13) is obtained by reaction of 1-ip with CO (1 atm) in CH2Cl2, whereas the isomer cis,cis-[Ru(η1-OAc)2(DiPPF)(CO)2] (14) can be prepared from carbonylation of 10. When 13 is heated in the solid state, 10 is formed by decarbonylation. These complexes promote the transfer hydrogenation of acetophenone in 2-propanol (S/C = 1000-2000) with NaOiPr (2 mol %), affording a TOF value of up to 81000 h-1 for complex 9 at 30 °C. Complex 10 catalyzes the head-to-head dimerization of terminal alkynes to 1,4-enynes in toluene at reflux with high stereoselectivity for the kinetic Z isomer
Efficient, Facile, and Green Synthesis of Ruthenium Carboxylate Complexes by Manual Grinding
Full text linkRecently, scientists have been developing sustainable processes, and in this context, mechanochemistry is commonly associated with green chemistry for its ability to reduce waste generation from chemical reactions. The well-known acetate complex, diacetate bis(triphenylphosphine) ruthenium(II) [Ru(OAc)2(PPh3)2], is a versatile precursor for preparing active complexes for several catalytic reactions. This report presents an efficient and straightforward manual grinding protocol for the sustainable synthesis of ruthenium carboxylate complexes starting from the commercially available [RuCl2(PPh3)3] and metal carboxylates. This work represents a novel and preliminary investigation into carboxylate precursors’ alternative solventless synthesis route based on manual grinding. To our knowledge, this is the first time [Ru(OAc)2(PPh3)2] has been prepared via a mechanochemical procedure. The synthesis method has also been investigated for other alkali metal carboxylates and yields ranging from 30 to 80% were obtained. A comparison of sustainability and environmental impact between conventional solution synthesis and the grinding route has been carried out using the E-factor and Mass Productivity. While for the acetate complex E-factor and MP were only slightly better compared with the solvent method (3 vs. 4 for E-factor and ~6 vs. 5 for MP), for benzoate higher results were found (1 vs. ~4 for E-factor and 10 vs. 5 for MP)
Diffusion Nuclear Magnetic Resonance Measurements on Cationic Gold (I) Complexes in Catalytic Conditions: Counterion and Solvent Effects
Full text linkThe amount of free ions, ion pairs, and higher aggregate of the possible species present in a solution during the gold(I)-catalyzed alkoxylation of unsaturated hydrocarbon, i.e., ISIP (inner sphere ion pair) [(NHC)AuX] and OSIP (outer sphere ion pairs) [(NHC)Au(TME)X] [NHC 1,3-bis(2,6-di-isopropylphenyl)-imidazol-2-ylidene; TME = tetramethylethylene (2,3-bis methyl-butene); X- = Cl-, BF4-, OTf-; and OTs- BArF4- (ArF = 3,5-(CF3)2C6H3)], has been determined. The 1H and 19F DOSY NMR measurements conducted in catalytic conditions indicate that the dissociation degree (alpha) of the equilibrium ion pair/free ions {[(NHC)Au(TME)X] [(NHC)Au(TME)]+ + X-} depends on the nature of the counterion (X-) when chloroform is the catalytic solvent: while the compounds containing OTs- and OTf- as the counterion gave a low alpha (which means a high number of ion pairs) of 0.13 and 0.24, respectively, the compounds containing BF4- and BArF4- showed higher alpha values of 0.36 and 0.32, respectively. These results experimentally confirm previous deductions based on catalytic and theoretical data: the lower the alpha value, the greater the catalytic activity because the anion that can activate methanol during a nucleophilic attack, although the lower propensity to activate methanol of BF4- and BArF4-, as suggested by the DFT calculations, cannot be completely overlooked. As for the effect of the solvent, alpha increases as the dielectric constant increases, as expected, and in particular, green solvents with high dielectric constants show a very high alpha (0.90, 0.84, 0.80, and 0.70 for propylene carbonate, gamma-valerolactone, acetone, and methanol, respectively), thus confirming that the moderately high activity of NHC-Au-OTf in these solvents is due to the specific effect of polar functionalities (O-H, C=O, O-R) in activating methanol. Finally, the DOSY measurements conducted in p-Cymene show the formation of quadrupole species: under these conditions, the anion can better exercise its 'template' and 'activating' roles, giving the highest TOF
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