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    C-C coupling formation using nitron complexes
    (Royal Soc Chemistry, 2020) Sevim, Mehmet; Kavukcu, Serdar Batikan; Kinal, Armagan; Sahin, Onur; Turkmen, Hayati
    A series of Ru-II (1), Rh-III (2), Ir-III (3, 4), Ir-I (5) and Pd-II (6-9) complexes of the 'instant carbene' nitron were prepared and characterized by H-1- and C-13-NMR, FT-IR and elemental analysis. The molecular structures of complexes 1-4 and 6 were determined by X-ray diffraction studies. The catalytic activity of the complexes (1-9) was evaluated in alpha(alpha)-alkylation reactions of ketones with alcohol via the borrowing hydrogen strategy under mild conditions. These complexes were able to perform this catalytic transformation in a short time with low catalyst and base amounts under an air atmosphere. Also, the Pd-II-nitron complexes (6-9) were applied in the Suzuki-Miyaura C-C coupling reaction and these complexes successfully initiated this reaction in a short time (30 minutes) using the H2O/2-propanol (1.5 : 0.5) solvent system. The DFT calculations revealed that the Pd-0/II/0 pathway was more preferable for the mechanism.
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    Comparison of Ru(II)-arene complexes containing naphthyl-/ quinolinyl-substituted ligand vis-a-vis structure, spectra and catalytic activity
    (Elsevier, 2024) Turkmen, Gulsah; Cakir, Sinem; Kavukcu, Serdar Batikan; Sahin, Onur; Turkmen, Hayati
    A series of ligands with naphthyl/quinolinyl substituent in their principal molecular framework were synthesised. Their corresponding half -sandwich ruthenium (Ru) complexes ( Ru 1a-b , Ru 2a-b and Ru 3 ) were then successfully generated. The structure of all synthesised compounds was comprehensively elucidated via 1 H and 13 C nuclear magnetic resonance (NMR), elemental analysis and Fourier -transform infrared spectroscopies. Notably, the structural configuration of Ru 3 was delineated via X-ray diffraction. The catalytic efficacy of the Ru complexes was systematically probed in two distinct reactions: 1) transfer hydrogenation (TH) of ketones using 2-propanol as the hydrogen source and 2) reduction of nitroarenes to anilines using sodium tetrahydridoborate as the reducing agent in ethanol, conducted at ambient temperature. Comparative analysis of catalytic yields of the Ru complexes ( Ru 1a-b , Ru 2a-b and Ru 3 ) in both reaction types revealed that Ru 3 delivered superior catalytic performance in both types of reactions. Furthermore, scrutiny of the 1 H NMR spectrum during the TH reaction revealed formation of Ru-hydride species.
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    Di- and tri-nuclear-palladium complexes bearing piperidoimidazolin-2-ylidenes: synthesis, characterization, and catalytic applications
    (Pergamon-Elsevier Science Ltd, 2015) Turkmen, Gulsah; Atik, Aylin; Sahin, Zarife Sibel; Turkmen, Hayati
    A series of di- and tri-nuclear Pd(II) complexes with piperidoimidazolin-2-ylidenes anchored to benzene ring via methylene spacers were synthesized. The obtained complexes were fully characterized by IR, H-1 NMR, C-13 NMR spectroscopy and elemental analysis. Molecular structures of two of the products have been determined by means of X-ray crystallography. Their catalytic performances in Suzuki-Miyaura and Mizoroki-Heck cross-coupling reactions were thoroughly investigated. The catalytic reactivity of new di- and tri-metallic complexes was compared with the monometallic systems. It is observed that the activities of the tri-nuclear Pd(NHC) complexes were higher than the corresponding mono- and di-nuclear complexes under the same conditions. (C) 2015 Elsevier Ltd. All rights reserved.
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    N-Alkylation and N-Methylation of Amines with Alcohols Catalyzed by Nitrile-Substituted NHC-Ir(III) and NHC-Ru(II) Complexes
    (Amer Chemical Soc, 2023) Cakir, Sinem; Kavukcu, Serdar Batikan; Sahin, Onur; Gunnaz, Salih; Turkmen, Hayati
    A series of nitrile-modified N-heterocyclic carbene (NHC) complexes of Ir(III) (2a-e) and Ru(II) (3a-d) have been prepared by transmetallation of [IrCp*Cl2]2 and [RuCl2(p-cymene)]2 forming an in situ NHC-Ag complex. The structures of all complexes were characterized by 1H NMR, 13C NMR, and Fourier transform infrared (FT-IR) spectroscopies. And the structures were clearly elucidated by performing X-ray diffraction studies on 2b, 3a, and 3c single crystals. The complexes of NHC- Ir(III) (2a-e) and NHC-Ru(II) (3a-d) were investigated in the N-alkylation reaction of aniline derivatives with benzyl alcohols to form N-benzyl amines and in the N-methylation reaction of aniline derivatives with methanol. Both reactions were performed in solvent-free media. The Ir(III) complexes (2a-e) were found to perform essentially better than similar Ru(II) complexes (3a-d) in the N-alkylation and N-methylation reactions. Among the Ir(III) complexes (2a-e), the best results were obtained with 2b. The catalytic mechanisms of both reactions were revealed by 1H NMR study. Formation of Ir-hydride species was observed for both reactions. This new report provides useful information to evaluate the activity of complexes and the differences in sensitivity between the NHCs.
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    Piano-stool benzothiazol-2-ylidene Ru(II) complexes for effective transfer hydrogenation of carbonyls
    (Elsevier Science Sa, 2016) Oruc, Zeynep Ipek; Gok, Lutfiye; Turkmen, Hayati; Sahin, Onur; Buyukgungor, Orhan; Cetinkaya, Bekir
    Benzothiazolium bromides (NSHC center dot HBr) (1a-j) with a variety of alkyl chain or benzyl substituents on N atom were prepared. The synthesis of ruthenium(II) (NSHC) complexes, (2a-j) could be achieved by in situ deprotonation of benzothiazolium salts with Ag2O and [RuCl2(p-cymene)](2). They were characterized by H-1, C-13, F-19 NMR, IR spectroscopy and elemental analysis. The molecular structures of 2d, 2e and 2g were ascertained by single-crystal X-ray diffraction studies. The catalytic properties of complexes, (2aej), with electron-donating or -withdrawing groups were investigated in transfer hydrogenation (TH) of ketones, and aldehydes with good to excellent yields. The presence of the CH2(CH2)(16)CH3 or CH2C6F5 on the N atom of the benzothiazol-2-ylidene complexes (2g, 2j) showed the highest activity for TH reaction. The catalytic properties of the N-alkyl substituted ruthenium(II) (NSHC) complexes(2h-j) may be interpreted by micelle effects. (C) 2016 Elsevier B.V. All rights reserved.
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    Piano-stool Ru (II) arene complexes that contain ethylenediamine and application in alpha-alkylation reaction of ketones with alcohols
    (Wiley, 2019) Kavukcu, Serdar Batikan; Gunnaz, Salih; Sahin, Onur; Turkmen, Hayati
    A series of piano-stool Ru (II) complexes (Ru1-7) bearing ethylenediamine with aryl and aliphatic groups were prepared and fully characterized by H-1, C-13, F-19 and P-31 NMR spectroscopy, FT-IR and elemental analysis. The crystal structures of Ru2-4 and Ru-7 were determined by X-ray crystallography. They were successfully applied to the alpha(alpha)-alkylation of aliphatic and aromatic ketones with alcohols via the borrowing hydrogen strategy in mild reaction conditions within a short time. The catalytic system has a broad substrate scope, which allows the synthesis of alpha alkylated ketones with excellent yields. The electronic and steric effects of complexes on catalytic activity were analysed. The influence of the carbon chain length of the ligand on the alpha-alkylation reaction of ketones was also investigated. The catalytic cycle was also examined by H-1-NMR spectroscopy in d(8)-toluene.
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    Synthesis and catalytic applications of Ru and Ir complexes containing N,O-chelating ligand
    (Elsevier Science Sa, 2020) Pakyapan, Bilge; Kavukcu, Serdar Batikan; Sahin, Zarife Sibel; Turkmen, Hayati
    A series of monometallic complexes (Ru1-3, Ir-1(-3)) which have N,O-chelating ligand (pyrazine-2carboxylate (1), pyridine-2-carboxylate (2), quinoline carboxylate(3) and bimetallic complexes (Ru-4,Ru-5, Ir-4(,5)) bridged by pyrazine-2,3- dicarboxylate (4) and imidazole-4,5-dicarboxylate(5) were synthesized and characterized by H-1-, C-13 NMR, FT-IR, and elemental analysis. The crystal structure of Ir-2 was determined by X-ray crystallography. The complexes (Ru1-5, Ir1-5) were applied to investigate the electronic and steric effect of ligand in their catalytic activities in transfer hydrogenation and alpha(alpha)-alkylation reaction of ketones with alcohols. The activities of iridium complexes (Ir1-5) were much more efficient than ruthenium complexes (Ru1-5). The highest activity for both reactions was observed for the complex (Ir2 ) with pyridine-2-carboxylate. The Ir hydride species was monitored for both reactions. (C) 2020 Elsevier B.V. All rights reserved.
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    The imidazo{[4,5-f][1,10]-phenanthrolin}l-2-ylidene and its palladium complexes: Synthesis, characterization, and application in C-C cross-coupling reactions
    (Elsevier Science Sa, 2017) Gok, Lutfiye; Gunnaz, Salih; Sahin, Zarife Sibel; Pelit, Levent; Turkmen, Hayati
    1,3-dibutyl-1H-imidazo[4,5-f][1,10]phenanthrolinium iodide, L-5 center dot 2HI ligand and their mono-, di-, tri-, tetra-nuclear palladium(II) complexes (5 center dot HPF6, 6-8) were synthesized and characterized by elemental analysis, FTIR, UV-visible and NMR spectroscopy. In addition, the complexes (5 center dot HPF6, 6-8) were determined by mass spectrometry (MALDI). The ligand L-5 center dot 2HI was determined by X-ray diffraction. The complexes (5 center dot HPF6, 6-8) were tested in Suzuki-Miyaura and Mizoroki-Heck reactions at elevated temperatures. The activities of the catalysts were monitored by NMR and GC analysis. We found that the poly-nuclear complexes display better activities compared to the mono-nuclear derivatives, thus proposing that an increase in metal moieties which leads to an increase in activity in cross-coupling reaction. (C) 2016 Elsevier B.V. All rights reserved.