DSpace Arşivi :: by Yazar "Ozkar, Saim" değerine göre listeleniyor

Yazar "Ozkar, Saim" seçeneğine göre listele

Listeleniyor 1 - 20 / 23

Aminophosphine-palladium(II) complexes: Synthsesis, structure and applications in Suzuki and Heck cross-coupling reactions
(Elsevier Science Sa, 2011) Aydemir, Murat; Baysal, Akin; Sahin, Ertan; Gumgum, Bahattin; Ozkar, Saim
Reaction of furfurylamine with 1 or 2 equivalents of PPh2Cl in the presence of Et3N, proceeds under anaerobic conditions in thf to give furfuryl-2-(N-diphenylphosphino)amine, Ph2PNHCH2-C4H3O, 1 and furfuryl-2-(N,N-bis(diphenylphosphino)amine), (Ph2P)(2)NCH2-C4H3O, 2, respectively. The reactions of 1 and 2 with MCl2(cod) (M = Pd, Pt; cod = 1,5-cyclooctadiene) or Pt(CH3)(2)(cod) yield complexes [M(Ph2PNHCH2-C4H3O)(2)Cl-2] (M= Pd 1a, Pt 1b), [Pt(Ph2PNHCH2-C4H3O)(2)(CH3)(2)] (1c), and [M((Ph2P)(2) NCH2-C4H3O)Cl-2] (M= Pd 2a, Pt 2b), [Pt((Ph2P)(2)NCH2-C4H3O)(CH3)(2)] (2c), respectively. All the compounds were isolated as analytically pure substances and characterized by NMR, IR spectroscopy and elemental analysis. Representative solid-state structures of 2a and 2b were also determined by X-ray single crystal diffraction technique. Furthermore, the palladium complexes 1a and 2a were tested and found to be highly active catalysts in the Suzuki coupling and Heck reaction affording biphenyls and trans-stilbenes, respectively. (C) 2011 Elsevier B.V. All rights reserved.
Ceria supported rhodium nanoparticles: Superb catalytic activity in hydrogen generation from the hydrolysis of ammonia borane
(Elsevier Science Bv, 2016) Akbayrak, Serdar; Tonbul, Yalcin; Ozkar, Saim
We investigated the effect of various oxide supports on the catalytic activity of rhodium nanoparticles in hydrogen generation from the hydrolysis of ammonia borane. Among the oxide supports (CeO2, SiO2, Al2O3, TiO2, ZrO2, HfO2) ceria provides the highest catalytic activity for the rhodium(0) nanoparticles in the hydrolysis of ammonia borane. Rhodium(0) nanoparticles supported on nanoceria (Rh-0/CeO2) were prepared by the impregnation of rhodium(III) ions on the surface of ceria followed by their reduction with sodium borohydride in aqueous solution at room temperature. They were isolated from the reaction solution by centrifugation and characterized by a combination of advanced analytical techniques. The catalytic activity of Rh-0/CeO2 samples with various rhodium loading in the range of 0.1-4.0% wt. Rh was also tested in hydrogen generation from the hydrolysis of ammonia borane at room temperature. The highest catalytic activity was achieved by using 0.1% wt. rhodium loaded nanoceria. The resulting Rh-0/CeO2 with a metal loading of 0.1% wt. Rh show superb catalytic activity in hydrogen generation from the hydrolysis of ammonia borane with a record turnover frequency value (TOF) of 2010 min(-1) at 25.0 +/- 0.1 degrees C. The superb catalytic activity of Rh-0/CeO2 is ascribed to the reducible nature of ceria. The reduction of cerium(IV) to cerium(III) leads to a build-up of negative charge on the oxide surface which favors the bonding of rhodium(0) nanoparticles on the surface and, thus, their catalytic activity. Rh-0/CeO2 are also reusable catalysts preserving 67% of their initial catalytic activity even after the fifth use in hydrogen generation from the hydrolysis of ammonia borane at room temperature (TOF= 1350 min(-1). The work reported here also includes the kinetic studies depending on the temperature to determine the activation energy (E-a = 43 +/- 2 kJ/mol) and the effect of catalyst concentration on the rate of hydrolysis of ammonia borane. (C) 2016 Elsevier B.V. All rights reserved.
Ceria-supported ruthenium nanoparticles as highly active and long-lived catalysts in hydrogen generation from the hydrolysis of ammonia borane
(Royal Soc Chemistry, 2016) Akbayrak, Serdar; Tonbul, Yalcin; Ozkar, Saim
Ruthenium(0) nanoparticles supported on ceria (Ru-0/CeO2) were in situ generated from the reduction of ruthenium(III) ions impregnated on ceria during the hydrolysis of ammonia borane. Ru-0/CeO2 was isolated from the reaction solution by centrifugation and characterized by ICP-OES, BET, XRD, TEM, SEM-EDS and XPS techniques. All the results reveal that ruthenium(0) nanoparticles were successfully supported on ceria and the resulting Ru-0/CeO2 is a highly active, reusable and long-lived catalyst for hydrogen generation from the hydrolysis of ammonia borane with a turnover frequency value of 361 min(-1). The reusability tests reveal that Ru-0/CeO2 is still active in the subsequent runs of hydrolysis of ammonia borane preserving 60% of the initial catalytic activity even after the fifth run. Ru-0/CeO2 provides a superior catalytic lifetime (TTO = 135 100) in hydrogen generation from the hydrolysis of ammonia borane at 25.0 +/- 0.1 degrees C before deactivation. The work reported here includes the formation kinetics of ruthenium(0) nanoparticles. The rate constants for the slow nucleation and autocatalytic surface growth of ruthenium(0) nanoparticles were obtained using hydrogen evolution as a reporter reaction. An evaluation of rate constants at various temperatures enabled the estimation of activation energies for both the reactions, E-a = 60 +/- 7 kJ mol(-1) for the nucleation and E-a = 47 +/- 2 kJ mol(-1) for the autocatalytic surface growth of ruthenium(0) nanoparticles, as well as the activation energy of E-a = 51 +/- 2 kJ mol(-1) for the catalytic hydrolysis of ammonia borane.
Dihydrogen Phosphate Stabilized Ruthenium(0) Nanoparticles: Efficient Nanocatalyst for The Hydrolysis of Ammonia-Borane at Room Temperature
(Mdpi Ag, 2015) Durap, Feyyaz; Caliskan, Salim; Ozkar, Saim; Karakas, Kadir; Zahmakiran, Mehmet
Intensive efforts have been devoted to the development of new materials for safe and efficient hydrogen storage. Among them, ammonia-borane appears to be a promising candidate due to its high gravimetric hydrogen storage capacity. Ammonia-borane can release hydrogen on hydrolysis in aqueous solution under mild conditions in the presence of a suitable catalyst. Herein, we report the synthesis of ruthenium(0) nanoparticles stabilized by dihydrogenphosphate anions with an average particle size of 2.9 +/- 0.9 nm acting as a water-dispersible nanocatalyst in the hydrolysis of ammonia-borane. They provide an initial turnover frequency (TOF) value of 80 min(-1) in hydrogen generation from the hydrolysis of ammonia-borane at room temperature. Moreover, the high stability of these ruthenium(0) nanoparticles makes them long-lived and reusable nanocatalysts for the hydrolysis of ammonia-borane. They provide 56,800 total turnovers and retain similar to 80% of their initial activity even at the fifth catalytic run in the hydrolysis of ammonia-borane at room temperature.
Group 4 oxides supported Rhodium(0) catalysts in hydrolytic dehydrogenation of ammonia borane
(Pergamon-Elsevier Science Ltd, 2019) Tonbul, Yalcin; Akbayrak, Serdar; Ozkar, Saim
Rh3+ ions are first impregnated on Group 4 metal oxides (TiO2, ZrO2, HfO2) in aqueous solution and, then reduced with aqueous solution of NaBH4 to form rhodium(0) nanoparticles (NPs) on the oxide surface. The analyses reveal that Rh(0) NPs are highly dispersed on the surface of TiO2, ZrO2, HfO2. Rh-0/MO2 (M: Ti, Zr, Hf) NPs have high activity and reusability in releasing H-2 from the hydrolysis of ammonia borane with an initial turnover frequency of 643, 198, and 188 min(-1), respectively, at 25.0 +/- 0.1 degrees C. The reusability of Rh-0/ZrO2 and Rh-0/HfO2 catalysts is higher than that of the Rh-0/TiO2 catalyst. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Hydrogen liberation from the hydrolytic dehydrogenation of dimethylamine-borane at room temperature by using a novel ruthenium nanocatalyst
(Royal Soc Chemistry, 2012) Caliskan, Salim; Zahmakiran, Mehmet; Durap, Feyyaz; Ozkar, Saim
Herein we report the discovery of an in situ generated, highly active nanocatalyst for the room temperature dehydrogenation of dimethylamine-borane in water. The new catalyst system consisting of ruthenium(0) nanoparticles stabilized by the hydrogenphosphate anion can readily and reproducibly be formed under in situ conditions from the dimethylamine-borane reduction of a ruthenium(III) precatalyst in tetrabutylammonium dihydrogenphosphate solution at 25 +/- 0.1 degrees C. These new water dispersible ruthenium nanoparticles were characterized by using a combination of advanced analytical techniques. The results show the formation of well-dispersed ruthenium(0) nanoparticles of 2.9 +/- 0.9 nm size stabilized by the hydrogenphosphate anion in aqueous solution. The resulting ruthenium(0) nanoparticles act as a highly active catalyst in the generation of 3.0 equiv. of H-2 from the hydrolytic dehydrogenation of dimethylamine-borane with an initial TOF value of 500 h(-1) at 25 +/- 0.1 degrees C. Moreover, they provide exceptional catalytic lifetime (TTO = 11 600) in the same reaction at room temperature. The work reported here also includes the following results; (i) monitoring the formation kinetics of the in situ generated ruthenium nanoparticles, by using the hydrogen generation from the hydrolytic dehydrogenation of dimethylamine-borane as a catalytic reporter reaction, shows that sigmoidal kinetics of catalyst formation and concomitant dehydrogenation fits well to the two-step, slow nucleation and then autocatalytic surface growth mechanism, A -> B (rate constant k(1)) and A + B -> 2B (rate constant k(2)), in which A is RuCl3 center dot 3H(2)O and B is the growing, catalytically active Ru(0)(n) nanoclusters. (ii) Hg(0) poisoning coupled with activity measurements after solution infiltration demonstrates that the in situ generated ruthenium(0) nanoparticles act as a kinetically competent heterogeneous catalyst in hydrogen generation from the hydrolytic dehydrogenation of dimethylamine-borane. (iii) A compilation of kinetic data depending on the temperature and catalyst concentration is used to determine the dependency of reaction rate on catalyst concentration and the activation energy of the reaction, respectively.
Iridium(O) nanoparticles dispersed in zeolite framework: A highly active and long-lived green nanocatalyst for-the hydrogenation of neat aromatics at room temperature
(Elsevier, 2014) Tonbul, Yalcin; Zahmakiran, Mehmet; Ozkar, Saim
The complete hydrogenation of aromatic molecules is one of the key transformation employed in the synthetic and petroleum chemistry. Described herein is a new catalytic nanomaterial for the hydrogenation of neat aromatics under mild conditions. A novel nanocatalyst, consisting of iridium(O) nanoparticles stabilized by zeolite with EAU framework could reproducibly been prepared from the reduction of iridium(III)-exchanged zeolite in an aqueous sodium borohydride solution at room temperature and characterized by ICP-MS, P-XRD, HRTEM, XPS, N-2-Ads.-Des., and P(C6H11)(3) poisoning. The results reveal the formation of iridium(O) nanoparticles of 5.8 +/- 2.1 nm size dispersed on the external surface along with iridium(O) nanolclusters in cavities of zeolite-Y whereby the host matrix remains intact. The resulting iridium(O) nanoparticles were employed as heterogeneous catalyst in the hydrogenation of various aromatic substrates (benzene, toluene, o-xylene and mesitylene) in the solvent-free systems at room temperature and 3 bar initial Hy pressure. They are highly active catalyst in the hydrogenation of neat aromatics, such as they can completely hydrogenate benzene to cyclohexane with an initial turnover frequency value of TOE= 3215 h(-1). Moreover, they show high durability against to leaching and sintering throughout the catalytic runs, which make them reusable catalyst. More importantly, testing the catalytic lifetime of our iridium(O) nanoparticles showed that they provide previously unprecedented total turnover number of TO = 197,000 over 92 h before deactivation in the hydrogenation of benzene at room temperature and 3 bar initial H-2 pressure. (C) 2013 Elsevier B.V. All rights reserved.
Magnetically Separable Rh0/Co3O4 Nanocatalyst Provides over a Million Turnovers in Hydrogen Release from Ammonia Borane
(Amer Chemical Soc, 2020) Akbayrak, Serdar; Tonbul, Yalcin; Ozkar, Saim
Cobalt(II,III) oxide nanopowders are used as supporting materials for rhodium(0) nanoparticles forming Rh-0/Co3O4 nanocatalysts, which can be prepared by impregnation and sodium borohydride reduction of Rh3+ ions on the surface of the oxide support. Magnetically separable Rh-0/Co3O4 nanoparticles are isolated from the reaction medium by an external magnet and characterized using various analytical techniques. Rh-0/Co3O4 nanoparticles are highly active and reusable catalysts with a long lifetime in hydrolytic dehydrogenation of ammonia borane (AB) at room temperature. Rh-0/Co3O4 nanoparticles with 0.5% wt Rh loading provide a turnover frequency of 1800 min(-1) and a total of 1.02 x 10(6) turnovers for H-2 evolution from the hydrolysis of AB at 25.0 +/- 0.1 degrees C. This turnover frequency is the second best value ever reported for the hydrolysis of AB, and the total turnover number of over a million is a record lifetime ever reported. Magnetically separable rhodium(0) nanoparticles are expectedly highly reusable catalysts and preserve their initial activity after the fifth run of hydrolysis. We also report the results of our study on the catalytic activity of Co3O4 nanopowders for the same dehydrogenation reaction.
Magnetically separable rhodium nanoparticles as catalysts for releasing hydrogen from the hydrolysis of ammonia borane
(Academic Press Inc Elsevier Science, 2019) Tonbul, Yalcin; Akbayrak, Serdar; Ozkar, Saim
Magnetically separable catalysts attract considerable attention in catalysis due to their facile separation from the reaction medium. This propensity is crucial for efficient multiple use of precious noble metal nanoparticles in catalysis. In fact, the isolation of catalysts from the reaction medium by filtration and washing results usually in the loss of huge amount of activity in the subsequent run of catalysis. Although many transition metal nanoparticle catalysts have been reported for the H-2 generation from the hydrolysis of ammonia borane, there is no study reporting the magnetically separable rhodium based catalysts for the hydrolytic dehydrogenation of ammonia borane. Here, we report the preparation of rhodium(0) nanoparticles supported on the surface of Fe3O4 and CoFe2O4 magnetic nanopowders as the first example of magnetically separable rhodium nanocatalysts. The resulting magnetically separable Rh-0/Fe3O4 and Rh-0/CoFe2O4 nanoparticles are highly active, long-lived and reusable catalysts in H-2 generation from the hydrolysis of ammonia borane providing a turnover frequency value of 273 and 720 min(-1), respectively, at 25.0 +/- 0.1 degrees C. These magnetically separable catalysts show high reusability and long-term stability in the hydrolysis reaction. They retain their complete initial activity even after the 5th use releasing exactly 3.0 equivalent H-2 gas per mole of ammonia borane. The long-term stability tests show that Rh-0/Fe3O4 and Rh-0/CoFe2O4 nanoparticles provide a total turnover number of 125,000 and 245,000, respectively, in releasing H-2 from the hydrolysis of ammonia borane at room temperature. The long term stability and reusability of magnetically separable Rh-0/Fe3O4 and Rh-0/CoFe2O4 nanopartides make them attractive catalysts for hydrogen generation in fuel cell applications. (C) 2019 Elsevier Inc. All rights reserved.
Nanoceria supported palladium(0) nanoparticles: Superb catalyst in dehydrogenation of formic acid at room temperature
(Elsevier Science Bv, 2017) Akbayrak, Serdar; Tonbul, Yalcin; Ozkar, Saim
Highly efficient dehydrogenation of formic acid (FA) at room temperature was achieved using palladium(0) nanoparticles supported on nanoceria (Pd-0/CeO2) as catalysts. Pd-0/CeO2 was prepared by impregnation of palladium(II) ions on the surface of ceria followed by their reduction with sodium borohydride in aqueous solution at room temperature. Pd((0)/CeO2 was isolated from the reaction solution by centrifugation and characterized by a combination of advanced analytical techniques. The catalytic activity of Pd-0/CeO2 samples with various Pd loading in the range 1.0-5.0% wt was tested in dehydrogenation of formic acid plus sodium formate with a molar ratio of FA/SF = 1/9. Pd-0/CeO2 with Pd loading of 2.27% wt shows superb catalytic activity in dehydrogenation of FA with a turnover frequency (TOF) value of 1400 h(-1) at 25.0 +/- 0.1 degrees C. The superb catalytic activity of Pd-0/CeO2 is ascribed to the reducible nature of ceria during the decomposition of FA (HCO2H -> CO2+H-2). The kinetic data, obtained by measuring the volume of pure H-2 gas, could be converted to the change in concentration of FA by considering the equilibrium between the formate ion and formic acid (HCO2H reversible arrow HCOO- + H3O+). The FA concentration versus time data fit to the first order kinetics with respect to the FA concentration. (C) 2017 Elsevier B.V. All rights reserved.
Nanozirconia supported ruthenium(0) nanoparticles: Highly active and reusable catalyst in hydrolytic dehydrogenation of ammonia borane
(Academic Press Inc Elsevier Science, 2018) Tonbul, Yalcin; Akbayrak, Serdar; Ozkar, Saim
Nanozirconia supported ruthenium(0) nanoparticles (Ru-0/ZrO2) were prepared by impregnation of ruthenium(III) cations on the surface of zirconia followed by their reduction with sodium borohydride at room temperature. Ru-0/ZrO2 was isolated from the reaction solution by centrifugation and characterized by ICP-OES, XRD, TEM, SEM EDS and XPS techniques. All the results reveal that ruthenium(0) nanoparticles were successfully supported on zirconia and the resulting Ru-0/ZrO2 is a highly active and reusable catalyst for hydrogen generation from the hydrolysis of ammonia borane with a turnover frequency value of 173 min(-1) at 25 degrees C. The reusability and catalytic lifetime tests reveal that Ru-0/ZrO2 is still active in the subsequent runs of hydrolysis of ammonia borane preserving 67% of the initial catalytic activity even after the fifth run and Ru-0/ZrO2 provides 72,500 turnovers (mol H-2/mol Ru) before deactivation at 25 degrees C. Our report also includes the results of kinetic studies depending on the catalyst concentration and temperature to determine the activation energy (E-a = 58 2 kJ/mol) for hydrolytic dehydrogenation of AB. (C) 2017 Elsevier Inc. All rights reserved.
Organometallic ruthenium, rhodium and iridium complexes containing a P-bound thiophene-2-(N-diphenylphosphino)methylamine ligand: Synthesis, molecular structure and catalytic activity
(Elsevier Science Sa, 2011) Aydemir, Murat; Baysal, Akin; Meric, Nermin; Kayan, Cezmi; Gumgum, Bahattin; Ozkar, Saim; Sahin, Ertan
Reaction of Ph2PNHCH2-C4H3S with [Ru(eta(6)-p-cymene)(mu-Cl)Cl](2), [Ru(eta(6)-benzene)(mu-Cl)Cl](2), [Rh(mu-Cl)(cod)](2) and [Ir(eta(5)-C5Me5)(mu-Cl)Cl](2) yields complexes [Ru(Ph2PNHCH2-C4H3S)(eta(6)-p-cymene)Cl-2], 1, [Ru(Ph2PNHCH2-C4H3S)(eta(6)-benzene)Cl-2], 2, [Rh(Ph2PNHCH2-C4H3S)(cod)Cl], 3 and [Ir(Ph2PNHCH2-C4H3S)(eta(5)-C5Me5)Cl-2], 4, respectively. All complexes were isolated from the reaction solution and fully characterized by analytical and spectroscopic methods. The structure of [Ru(Ph2PNHCH2-C4H3S)(eta(6)-benzene)Cl-2], 2 was also determined by single crystal X-ray diffraction. 1-4 are suitable precursors forming highly active catalyst in the transfer hydrogenation of a variety of simple ketones. Notably, the catalysts obtained by using the ruthenium complexes [Ru(Ph2PNHCH2-C4H3S)(eta(6)-p-cymene)Cl-2], 1 and [Ru(Ph2PNHCH2-C4H3S)(eta(6)-benzene)Cl-2], 2 are much more active in the transfer hydrogenation converting the carbonyls to the corresponding alcohols in 98-99% yields (TOF <= 200 h(-1)) in comparison to analogous rhodium and iridium complexes. (C) 2011 Elsevier B.V. All rights reserved.
Palladium(0) nanoclusters stabilized by poly(4-styrenesulfonic acid-co-maleic acid) as an effective catalyst for Suzuki-Miyaura cross-coupling reactions in water
(Elsevier, 2011) Metin, Onder; Durap, Feyyaz; Aydemir, Murat; Ozkar, Saim
Palladium(0) nanoclusters stabilized by poly(4-styrenesulfonic acid-co-maleic acid), PSSA-co-MA, were generated in situ during the hydrolysis of ammonia-borane (AB) from the reduction of potassium tetrachloropalladate(II) in aqueous solution at room temperature. They were isolated from the reaction solution and characterized by UV-visible electronic absorption spectroscopy, TEM, SAED and XRD techniques. The PSSA-co-MA stabilized palladium(0) nanoclusters were used as catalyst in Suzuki-Miyaura cross-coupling reactions of various of arylbromides or aryl iodide with phenylboronic acid in water without any purification process after catalytic hydrolysis of AB. They show excellent catalytic activity in coupling of series of aryl bromides or aryl iodide with phenylboronic acid under the optimized reaction conditions in water. PSSA-co-MA stabilized palladium(0) nanoclusters provided turnover frequency of 1980 and 5940h(-1) in Suzuki-Miyaura coupling reactions of phenylboronic acid with p-bromoacetophenone or p-iodobenzene, respectively, which are the highest values ever reported for the Suzuki-Miyaura coupling reactions in water as sole solvent. (C) 2011 Elsevier B.V. All rights reserved.
Palladium(0) nanoparticles supported on ceria: Highly active and reusable catalyst in hydrogen generation from the hydrolysis of ammonia borane
(Pergamon-Elsevier Science Ltd, 2016) Tonbul, Yalcin; Akbayrak, Serdar; Ozkar, Saim
Palladium(0) nanoparticles supported on nanoceria (Pd-0/CeO2) were prepared by the impregnation of palladium(II) ions on the surface of ceria followed by their reduction with sodium borohydride in aqueous solution at room temperature. Pd-0/CeO2 were isolated from the reaction solution by centrifugation and characterized by ICP-OES, XRD, TEM, SEM-EDS and XPS techniques. All the results reveal that palladium(0) nanoparticles were uniformly dispersed on ceria and the resulting Pd-0/CeO2 are highly active and reusable catalysts in hydrogen generation from the hydrolysis of ammonia borane with a turnover frequency value of 29 min(-1) at 25.0 +/- 0.1 degrees C. The catalytic activity of Pd-0/CeO2 in hydrogen generation from the hydrolysis of ammonia borane is higher compared to that of other palladium based catalysts such as Pd-0/ZrO2, Pd-0/SiO2, Pd-0/Al2O3, Pd-0/TiO2 under the same conditions. The catalytic activity of Pd-0/CeO2 samples with various palladium loading in the range of 1.0-5.0% wt Pd was tested in hydrogen generation from the hydrolysis of ammonia borane at 25.0 +/- 0.1 degrees C. The highest catalytic activity was achieved by using 1.18% wt palladium loaded ceria. The reusability tests reveal that Pd-0/CeO2 are still active in the subsequent runs of hydrolysis of ammonia borane preserving 47% of the initial catalytic activity even after the fifth run of hydrolysis. Our report also includes the results of kinetic study of the catalytic hydrolysis of ammonia borane depending on the temperature and catalyst concentration. (c) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Reducible tungsten(VI) oxide-supported ruthenium(0) nanoparticles: highly active catalyst for hydrolytic dehydrogenation of ammonia borane
(Tubitak Scientific & Technological Research Council Turkey, 2023) Akbayrak, Serdar; Tonbul, Yalcin; Ozkar, Saim
Reducible WO3 powder with a mean diameter of 100 nm is used as support to stabilize ruthenium(0) nanoparticles. Ruthenium(0) nanoparticles are obtained by NaBH4 reduction of ruthenium(III) precursor on the surface of WO3 support at room temperature. Ruthenium(0) nanoparticles are uniformly dispersed on the surface of tungsten(VI) oxide. The obtained Ru0/WO3 nanoparticles are found to be active catalysts in hydrolytic dehydrogenation of ammonia borane. The turnover frequency (TOF) values of the Ru0/WO3 nanocatalysts with the metal loading of 1.0%, 2.0%, and 3.0% wt. Ru are 122, 106, and 83 min-1, respectively, in releasing hydrogen gas from the hydrolysis of ammonia borane at 25.0 degrees C. As the Ru0/WO3 (1.0% wt. Ru) nanocatalyst with an average particle size of 2.6 nm provides the highest activity among them, it is extensively investigated. Although the Ru0/WO3 (1.0% wt. Ru) nanocatalyst is not magnetically separable, it has extremely high reusability in the hydrolysis reaction as it preserves 100% of initial catalytic activity even after the 5th run of hydrolysis. The high activity and reusability of Ru0/WO3 (1.0% wt. Ru) nanocatalyst are attributed to the favorable metal-support interaction between the ruthenium(0) nanoparticles and the reducible tungsten(VI) oxide. The high catalytic activity and high stability of Ru0/WO3 nanoparticles increase the catalytic efficiency of precious ruthenium in hydrolytic dehydrogenation of ammonia borane.
Room temperature aerobic Suzuki cross-coupling reactions in DMF/water mixture using zeolite confined palladium(0) nanoclusters as efficient and recyclable catalyst
(Elsevier, 2010) Durap, Feyyaz; Rakap, Murat; Aydemir, Murat; Ozkar, Saim
Herein we report the use of zeolite confined palladium(0) nanoclusters as efficient and recyclable catalyst for Suzuki cross-coupling reactions of aryl bromides with phenylboronic acid. Zeolite confined palladium(0) nanoclusters are highly active catalyst for the Suzuki cross-coupling reactions under mild conditions (room temperature, in air) in DMF/water (1:9) mixture. A variety of aryl bromides undergo Suzuki cross-coupling with phenylboronic acid with quantitative GC yields of biaryl derivatives. Recycling experiments showed that zeolite confined palladium(0) nanoclusters can be used as recyclable catalyst in the Suzuki cross-coupling reactions. (c) 2010 Elsevier B.V. All rights reserved.
Ruthenium complexes of aminophosphine ligands and their use as pre-catalysts in the transfer hydrogenation of aromatic ketones: X-ray crystal structure of thiophene-2-(N-diphenylthiophosphino)methylamine
(Pergamon-Elsevier Science Ltd, 2011) Aydemir, Murat; Baysal, Akin; Ozkar, Saim; Yildirim, Leyla Tatar
Reaction of thiophene-2-methylamine with one or two equivalents of PPh2Cl in the presence of NEt3, proceeds in thf to give thiophene-2-(N-diphenylphosphino)methylamine, la and thiophene-2-(N, N-bis(diphenylphosphino))methylamine, 2a respectively, under anaerobic conditions. Oxidations of la and 2a with aqueous hydrogen peroxide, elemental sulfur or gray selenium in thf gives the corresponding oxides, sulfides and selenides [Ph2P(E)NHCH2-C4H3S] (E: O 1b, S 1c, Se 1d) and [(Ph2P(E))(2)NCH2-C4H3S], (E: O 2b, S 2c, Se 2d) respectively, in high yield. Furthermore, two novel Ru(II) complexes with the P-N ligands la and 2a were synthesized starting with the complex [Ru(eta(6)-p-cymene)(mu-Cl)Cl](2). The complexes were fully characterized by analytical and spectroscopic methods. P-31-{H-1} NMR, DEPT, H-1-13C HETCOR or H-1-H-1 COSY correlation experiments were used to confirm the spectral assignments. The molecular structure of thiophene-2-(N-diphenylthiophosphino)methylamine was also elucidated by single-crystal X-ray crystallography. Following activation by NaOH, compounds 3 and 4 catalyze the transfer hydrogenation of acetophenone derivatives to 1-phenylethanol derivatives in the presence of iso-PrOH as the hydrogen source. [Ru(Ph2PNHCH2-C4H3S)(eta(6)-p-cymene)Cl-2], 3 and [Ru((PPh2)(2)NCH2-C4H3S)-(eta(6)-p-cymene)Cl]Cl, 4 complexes are suitable catalyst precursors for the transfer hydrogenation of acetophenone derivatives in 0.1 M iso-PrOH solution. Notably 4 acts as an excellent catalyst giving the corresponding alcohols in excellent conversions up to 99% (TOF <= 744 h(-1)). This transfer hydrogenation is characterized by low reversibility under the experimental conditions. (C) 2010 Elsevier Ltd. All rights reserved.
A ruthenium(II) bipyridine complex containing a 4,5-diazafluorene moiety: Synthesis, characterization and its applications in transfer hydrogenation of ketones and dye sensitized solar cells
(Pergamon-Elsevier Science Ltd, 2015) Baysal, Akin; Aydemir, Murat; Durap, Feyyaz; Ozkar, Saim; Yildirim, Leyla Tatar; Ocak, Yusuf Selim
The ruthenium(B) complex [Ru(bpy)(2)L](PF6)(2), where bpy is 2,2'-bipyridine and L is 1,5-dihydro-2-H-cyclopenta[1,2-b:5,4-b']dipyridine-2-one, was synthesized from the reaction of cis-Ru(bpy)(2)Cl-2 center dot 2H(2)O with L, and isolated as the hexafluorophosphate salt. The structure of L was unequivocally elucidated by single-crystal X-ray diffraction analysis. The new ruthenium(II) complex was thoroughly characterized by H-1 and C-13 NMR spectroscopy, along with FTIR, UV-Vis and LC MS/MS Triple Quadrupole Mass spectroscopy and elemental analysis. The catalytic activity of [Ru(bpy)(2)L](PF6)(2) was tested in the transfer hydrogenation of various ketones in 2-propanol as both the solvent and hydrogen donor. The usage of [Ru(bpy)(2)L](PF6)(2) for the formation of a dye sensitized solar cell is also presented. (C) 2015 Elsevier Ltd. All rights reserved.
Synthesis and characterization of new bis(diphenylphosphino)aniline ligands and their complexes: X-ray crystal structure of palladium(II) and platinum(II) complexes, and application of palladium(II) complexes as pre-catalysts in Heck and Suzuki cross-coupling reactions
(Pergamon-Elsevier Science Ltd, 2009) Aydemir, Murat; Durap, Feyyaz; Baysal, Akin; Akba, Osman; Gumgum, Bahattin; Ozkar, Saim; Yildirim, Leyla Tatar
Two new bis(diphenylphosphino)isopropylphenylamines, (PPh2)(2)N-C6H4-CH(CH3)(2), having the isopropyl substituent at the carbon atom 2 (1) or 4 (2), were prepared by the aminolysis of chlorodiphenylphosphine with isopropyl substituted aniline at the ortho- or para-position, respectively, under anaerobic conditions. Oxidation of 1 and 2 with either aqueous hydrogen peroxide, elemental sulfur or grey selenium in thf gave the corresponding oxides, sulfides and selenides (Ph2P=E)(2)N-C6H4-CH(CH3)(2), where E = O, S or Se, respectively. The palladium and platinum complexes [M{(Ph2P)(2)N-C6H4-CH(CH3)(2))Cl-2] (M = Pd, Pt) and the copper complex [Cu((Ph2P)(2)N-C6H4-CH(CH3)(2))(2)]PF6 were isolated from the reaction of the bis(phosphino)anilines with MCl2(cod) or [Cu(CH3CN)(4)]PF6, respectively. The new compounds were characterized by NMR, IR spectroscopy and elemental analysis. Furthermore, the solid-state structures of two representative complexes were determined using single crystal X-ray diffraction analysis. The compounds of palladium (1d) and platinum (1e), both mononuclear complexes, crystallize in the monoclinic P2(1)/c space group. In both compounds the metal ion has a distorted square-planar coordination geometry. The structural properties of complexes Id and le in the solid state are very similar. The palladium complexes were also tested for their catalytic activities in C-C coupling reactions. (C) 2009 Elsevier Ltd. All rights reserved.
Synthesis and structural characterization of a novel seven-coordinate cobalt(II) complex: 2,9-Bis(ethanolamine)-1,10-phenanthrolinechlorocobalt(II) chloride
(Elsevier Science Sa, 2011) Baysal, Akin; Aydemir, Murat; Durap, Feyyaz; Ozkar, Saim; Yildirim, Leyla Tatar
Condensation reaction of 2,9-dicarboxaldehyde-1,10-phenanthroline with 2-aminoethanol followed by NaBH4 reduction yielded the polydentate Schiff base ligand 2,9-bis(ethanolamine)-1,10-phenanthroline in its reduced form. This ligand was characterized by elemental analysis, LC-MS, IR, UV-Vis and NMR spectroscopy. Reaction of the reduced Schiff base ligand with aqueous solution of cobalt(II) chloride affords 2,9-bis(ethanolamine)-1,10-phenanthrolinechlorocobalt(II) chloride in high yield. Single crystals of the cobalt(II) complex were obtained from the crystallization in ethanol and its structure was elucidated by X-ray structural analysis. The cobalt(II) complex ion was found to be seven-coordinated in a pentagonal bipyramidal geometry, whereby cobalt(II) ion is surrounded by the six donor atoms in the ligand molecule and a chloride ion. (C) 2011 Elsevier B. V. All rights reserved.

Yazar "Ozkar, Saim" seçeneğine göre listele

Sayfa Başına Sonuç

Sıralama seçenekleri