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Öğe Asymmetric transfer hydrogenation reaction in water: Comparison of chiral proline amide/amine ruthenium(II) complexes(Elsevier Science Sa, 2015) Denizalti, Serpil; Mercan, Deniz; Sen, Betul; Gokce, Aytac Gurhan; Cetinkaya, BekirChiral proline amide/amine ligands (2, 3), synthesized by multi-step reaction starting from L-proline (1), were evaluated as catalyst generated in situ from [RuCl2(p-cymene)](2) for asymmetric transfer hydrogenation of aromatic ketones in the presence of sodium formiate and sodium dodecyl sulfate (SDS). The results revealed that efficiencies and enantioselectivities strongly depend on the N-substituents. (C) 2014 Elsevier B.V. All rights reserved.Öğe A highly novel dinickel complex: A hydrogen-bonded anti-skew carboxylate bridge and a 2D supramolecular structure(Elsevier Science Bv, 2009) Korkmaz, Neslihan; Gokce, Aytac Gurhan; Astley, Stephen T.; Aygun, Muhittin; Astley, Demet; Buyukgungor, OrhanReaction of the tridentate Schiff base ligands obtained from 2,4-dihydroxybenzaldehyde and either L-iso-leucine or L-tert-leucine with Ni(NO3)(2) in methanol/water solution in the presence of base afforded dinickel complexes. The crystal structure of the product derived from L-tert-leucine has been determined by X-ray crystallography. The octahedrally coordinated two Ni centers were found to be bridged by a single carboxylate group in an extremely unusual non-planar fashion. A 2D supramolecular structure, constructed by infinite hydrogen-bonded complex sheets parallel to the ab-plane of the unit cell, arises from intermolecular O-H center dot center dot center dot O hydrogen bonds. (C) 2009 Elsevier B.V. All rightsÖğe A highly novel dinickel complex: A hydrogen-bonded anti-skew carboxylate bridge and a 2D supramolecular structure(Elsevier Science Bv, 2009) Korkmaz, Neslihan; Gokce, Aytac Gurhan; Astley, Stephen T.; Aygun, Muhittin; Astley, Demet; Buyukgungor, OrhanReaction of the tridentate Schiff base ligands obtained from 2,4-dihydroxybenzaldehyde and either L-iso-leucine or L-tert-leucine with Ni(NO3)(2) in methanol/water solution in the presence of base afforded dinickel complexes. The crystal structure of the product derived from L-tert-leucine has been determined by X-ray crystallography. The octahedrally coordinated two Ni centers were found to be bridged by a single carboxylate group in an extremely unusual non-planar fashion. A 2D supramolecular structure, constructed by infinite hydrogen-bonded complex sheets parallel to the ab-plane of the unit cell, arises from intermolecular O-H center dot center dot center dot O hydrogen bonds. (C) 2009 Elsevier B.V. All rightsÖğe Hydroxyl and ester functionalized N-heterocyclic carbene complexes of iridium(I): efficient catalysts for transfer hydrogenation reactions(Royal Soc Chemistry, 2014) Gulcemal, Derya; Gokce, Aytac Gurhan; Gulcemal, Suleyman; Cetinkayaa, BekirHydroxyl and ester-functionalized iridium(I) complexes of N-heterocyclic carbenes (3a-e) were obtained by transmetalation reactions from the in situ prepared silver(I)-NHC complexes and characterized by IR, NMR, mass spectroscopies, and elemental analysis. X-ray diffraction studies on single crystals of 3a, 3c and 3d verify the square planar geometry at the iridium center. Ester functionalized iridium(I)-NHC complexes were found to be highly active and selective catalysts for the transfer hydrogenation reactions of various aldehydes and ketones. The influence of different ester substituents on the reactivity of the complexes was studied and the complex with a pivaloyl substituent (3d) showed the best activity (TON up to 10 000).Öğe Iridium(I) N-heterocyclic carbene complexes of benzimidazol-2-ylidene: effect of electron donating groups on the catalytic transfer hydrogenation reaction(Royal Soc Chemistry, 2013) Gulcemal, Suleyman; Gokce, Aytac Gurhan; Cetinkaya, BekirTwo new [Ir(NHC)(COD)Cl] (NHC = N-heterocyclic carbene; COD = 1,5-cyclooctadiene) iridium complexes (2a,b) have been prepared by the reaction of [Ir(COD) Cl](2) with in situ prepared NHC-Ag carbene transfer agents in dichloromethane at ambient temperature. They have been fully characterized by H-1, C-13 NMR, and elemental analysis. X-ray diffraction studies on single crystals of 2a and 2b confirm the square planar geometry. Complexes of type [Ir(NHC)(CO)(2)Cl] [NHC = 1,3-diisopropyl(5,6-dimethyl)benzimidazol-2-ylidene] 3 were also synthesized to compare sigma-donor/pi-acceptor strength of NHC ligands. Transfer hydrogenation (TH) reactions of various aldehydes and ketones have been studied using complexes 2a and 2b as catalysts. The 5,6-dimethyl substituted iridium complex (2b) showed the highest catalytic activity for the TH reaction.Öğe Iridium(I) N-heterocyclic carbene complexes of benzimidazol-2-ylidene: effect of electron donating groups on the catalytic transfer hydrogenation reaction(Royal Soc Chemistry, 2013) Gulcemal, Suleyman; Gokce, Aytac Gurhan; Cetinkaya, BekirTwo new [Ir(NHC)(COD)Cl] (NHC = N-heterocyclic carbene; COD = 1,5-cyclooctadiene) iridium complexes (2a,b) have been prepared by the reaction of [Ir(COD) Cl](2) with in situ prepared NHC-Ag carbene transfer agents in dichloromethane at ambient temperature. They have been fully characterized by H-1, C-13 NMR, and elemental analysis. X-ray diffraction studies on single crystals of 2a and 2b confirm the square planar geometry. Complexes of type [Ir(NHC)(CO)(2)Cl] [NHC = 1,3-diisopropyl(5,6-dimethyl)benzimidazol-2-ylidene] 3 were also synthesized to compare sigma-donor/pi-acceptor strength of NHC ligands. Transfer hydrogenation (TH) reactions of various aldehydes and ketones have been studied using complexes 2a and 2b as catalysts. The 5,6-dimethyl substituted iridium complex (2b) showed the highest catalytic activity for the TH reaction.Öğe N-Benzyl Substituted N-Heterocyclic Carbene Complexes of Iridium(I): Assessment in Transfer Hydrogenation Catalyst(Amer Chemical Soc, 2013) Gulcemal, Suleyman; Gokce, Aytac Gurhan; Cetinkaya, BekirIridium()) complexes of N-heterocyclic carbenes (NHCs) (1a-3a) were obtained by transmetalation reactions from the corresponding Ag(I)-NHC complexes. These complexes have been fully characterized by H-1, C-13, heteronuclear multiple-bond correlation NMR spectroscopies, and elemental analysis. X-ray diffraction studies on single crystals of la and 2a confirm the square planar geometry at the metal center. [IrCl(CO)(2)(NHC)] complexes 1b-3b were also synthesized to compare sigma-donor/pi-acceptor strength of NHC ligands. Transfer hydrogenation (TH) reactions of various ketones and imines have been studied using complexes 1a-3a as precatalysts. N-Benzyl substituted NHC complexes of Ir(I) proved to be highly efficient precatalysts in the reduction of aromatic and aliphatic ketones to afford the corresponding alcohol products with turnover frequencies values up to 24 000 h(-1).Öğe Preparation and crystal structure of binuclear chloro{6-[[chloro(triphenylphosphine)platinum](mesitylimino)methyl]pyridin-2-yl}bis(triphenylphosphine)platinum(II)(Pergamon-Elsevier Science Ltd, 2008) Gunay, M. Emin; Dayan, Osman; Gokce, Aytac Gurhan; Aygun, Muhittin; Cetinkaya, Bekir; Buyukgungor, OrhanTreatment of N,N'-bis(mesityl)pyridine-2,6-carboxyimidoyldichloride, 1, in toluene solution with [Pt(PPh3)(4)] at 100 degrees C afforded a novel platinacyclic compound, 3, in 63% yield, instead of the expected compound 2. The molecular and crystal structures of the title compound, 3, have been determined by the single crystal X-ray diffraction technique. The coordination geometries around the Pt atoms are distorted square-planar. In the crystal structure, the molecules are linked by a pair of C-H center dot center dot center dot N hydrogen bonds into a centrosymmetric dinner with an R-2(2) (16) ring, centred at (1/2,1/2,1/2). (C) 2008 Elsevier Ltd. All rights reserved.Öğe Ruthenium(II) complexes derived from 2-phenylthiazoline-4-carboxylic acid: structure and catalytic activity for transfer hydrogenation reaction(Wiley, 2016) Denizalti, Serpil; Sen, Betul; Gokce, Aytac Gurhan; Cetinkaya, BekirPiano-stool ([(p-cymene)Ru(thz)Cl], 2) and six-coordinated ([Ru(thz)(2)(PPh3)(2)], 3) ruthenium complexes derived from 2-phenylthiazoline-4-carboxylic acid (Hthz, 1) were synthesized for the first time, and fully characterized using conventional methods. Also, the molecular structure of complex 3 was determined using X-ray analysis. These complexes were evaluated as catalysts for transfer hydrogenation of carbonyl compounds in the presence of isopropyl alcohol and (KOBu)-Bu-t. Complex 2 was found to be more active than 3 in transfer hydrogenation. Copyright (c) 2016 John Wiley & Sons, Ltd.Öğe Sterically hindered N-aryl/benzyl substituted piperi doi midazolin-2-ylidene palladium complexes and their catalytic activities(Pergamon-Elsevier Science Ltd, 2018) Gacal, Elif; Denizalti, Serpil; Kinal, Armagan; Gokce, Aytac Gurhan; Turkmen, HayatiA series of N-aryl (2a,b) or benzyl (2c,d) substituted piperidoimidazolinium salts and their palladium complexes (3a-d) were prepared and characterized by H-1, C-13 NMR, IR spectroscopy and elemental analysis. The crystal structures of 3a and 3c have been determined by X-ray crystallography. Thermogravimetric analysis (TGA) was applied to complexes (3a-d). The palladium complexes have been employed as catalyst for Suzuki-Miyaura cross coupling. The N-aryl substituted complex 3b was a highly efficient precatalyst and successfully employed in Suzuki-Miyaura cross coupling reactions of (hetero) aryl chlorides with arylboronic acids in air. In addition, the oxidative addition step of the reaction mechanism involving chlorobenzene and the catalysts 3a, 3b, 3c and 3d were computationally investigated by the DFT-w-B97X-D method and complete agreement were obtained with the catalytic results. To measure alpha-donating and pi-acceptor properties of the new ligands, the rhodium carbonyl complexes were also prepared. (C) 2018 Elsevier Ltd. All rights reserved.Öğe Synthesis and structural characterization of Palladium(II) complex bearing N-Heterocyclic Carbene(Springer/Plenum Publishers, 2008) Gokce, Aytac Gurhan; Turkmen, Hayati; Aygun, Muhittin; Cetinkaya, Bekir; Buyuekgungor, OrhanTrcitts-Bis[1,3-bis(2,4-dimethylphenylimidazolidin-2-ylidene)]dichloropalladium(II), 4, was prepared from 1,3-bis(2,4-dimetilphenyl)imidazoliniumchloride. The crystal and molecular structure of 4 have been determined by single crystal X-ray diffraction. The title compound, C38H44N4PdCl2, crystalizes in the monoclinic space group P 21/n with a = 13.8713(9) angstrom, b = 12.1365(6) angstrom, c = 21.5499(15) angstrom The Pd atom has a slightly distorted square planar coordination geometry. The molecules of the title compound are I inked by C-H center dot center dot center dot Cl weak hydrogen bonds into two-dimensional sheets parallel to the (001) plane. In addition, the title compound was characterized by elemental analyses and NMR spectroscopy.Öğe Synthesis and structural characterization of trans-bis[1,3-bis(methoxyethyl)-4,5-bis(2,4,6-trimethylphenyl)imidazolidin-2-ylidene]dichloro-palladium(II)(Walter De Gruyter Gmbh, 2007) Gokce, Aytac Gurhan; Kilincarslan, Rafet; Aygun, Muhittin; Cetinkaya, Bekir; Garcia-Granda, SantiagoA Pd(II) complex of a new N-heterocyclic carbene (NHC) ligand with bulky substituents and functionalized methoxy-donor side arms has been synthesized and characterized by elemental analyses, H-1 and C-13 NMR, and IR spectroscopy. Molecular and crystal structures of the title complex have been determined by single crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P2(1/)c, with a = 15.927(2), b = 8.489(2), c = 20.309(5) angstrom, beta = 99.213(2)degrees, Z = 2, D-x = 1.253 g cm(-3). The palladium atom is situated on an inversion center. There are several weak intramolecular C-H... N/O interactions.Öğe Synthesis of bimetallic complexes bridged by 2,6-bis(benzimidazol-2-yl) pyridine derivatives and their catalytic properties in transfer hydrogenation(Royal Soc Chemistry, 2018) Gunnaz, Salih; Gokce, Aytac Gurhan; Turkmen, HayatiA series of binuclear rhodium(i) and iridium(i) complexes with 2,6-bis(benzimidazol-2-yl) pyridine (bzimpy) derivatives were synthesized and characterized by elemental analysis and spectroscopic methods. The molecular and crystal structures of complex 3d were determined by the single crystal X-ray diffraction technique. Their monometallic analogues were prepared to compare the catalytic properties of the bimetallic complexes. To determine the catalyst properties that result in a cooperative, bimetallic enhancement of the reaction rate, the systematic variation of the intermetallic distance and the ligand donor properties of the bimetallic complexes were explored based on the transfer hydrogenation reactions of ketones.Öğe X-ray structural analysis and catalytic properties of new thiazoline carboxylate ruthenium complexes(Int Union Crystallography, 2015) Sen, Betul; Denizalti, Serpil; Gokce, Aytac Gurhan; Aygun, Muhittin
