Effect of Initial Configuration on DFT Calculations for Transition Metal Complexes

Computational methods, which solves the Schrödinger’s equation for molecules, have become an indispensable tool in last decades. And Density Functional Theory is one of the most used, and most effective computational method. Transition Metal complexes, on the other hand, have been being used extensively in many important applications in many fields, such as chemical catalysts, atomic thin films, and pharmaceutical industry. Applying computational methods to transition metal complexes has become inevitable to understand better, to control and to design these compounds. As it is known, it is very difficult to handle transition metals computationally, mostly due to near degeneracy in their electronic states. The computational algorithms usually cannot achieve as successive result as they can do for other typical elements, like carbon or nitrogen for instance. Computational methods are needed to be improved for properly deal with transition metal complexes. To find computationally cheaper but still effective methods to deal with these complexes is a major challenge. Unlike the analogue calculations, computational methods solve all equations iteratively, so there are major differences between these two calculation types. The starting point in state space (the assumed initial conformation of molecule) is could have a stronger effect then the expected, on the flow of the iterative solving algorithm of the computational approach. Here we present a comparative study for a Ruthenium complex. We have optimised the molecule several times. Each of the optimisations started from different initial molecular conformations. Then we have compared the result in different ways, like calculation times and minimum energy that had reached, to see effect of starting configurations on the calculation. It is showed that, starting configuration is an important parameter for computational calculations of transition metal complexes, and it is needed to be carefully chosen to improve success of calculations

Zeolite confined copper(0) nanoclusters as cost-effective and reusable catalyst in hydrogen generation from the hydrolysis of ammonia-borane

Herein we report the development of a cost-effective nanocluster catalyst for the hydrolytic dehydrogenation of ammonia-borane which is considered to be one among the new hydrogen storage materials. Zeolite confined copper(0) nanoclusters were prepared by the ion-exchange of Cu2+ ions with the extra framework Na+ ions in zeolite-Y followed by reduction of the Cu2+ ions within the cavities of zeolite with sodium borohydride in aqueous solution and characterized by HR-TEM, XRD, XPS, SEM, EDX, ICP-OES, Raman spectroscopy and N-2 adsorption-desorption technique. Zeolite confined copper(0) nanoclusters are found to be active catalysts in the hydrolysis of ammonia-borane even at low temperatures (<= 15 degrees C) and stable enough for being isolated as solid materials. They provide 1300 turnovers in hydrogen generation from the hydrolysis of ammonia-borane at room temperature. The average value of turnover frequency is 46.5 h(-1) for the same reaction. More importantly, zeolite confined copper(0) nanoclusters were found to be isolable, bottleable and reusable catalysts in the hydrolytic dehydrogenation of ammonia-borane; even at fifth run the complete release of hydrogen from the hydrolysis of ammonia-borane at room temperature is achieved. The work reported here also includes the full experimental details for the collection of a wealth of kinetic data to determine the activation energy and the effect of catalyst concentration on the rate for the catalytic hydrolysis of ammonia-borane. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved

Water soluble laurate-stabilized ruthenium(0) nanoclusters catalyst for hydrogen generation from the hydrolysis of ammonia-borane: High activity and long lifetime

The simplest amine-borane, considered as solid hydrogen storage material, ammonia-borane (H(3)NBH(3)) can release hydrogen gas upon catalytic hydrolysis under mild conditions. Herein, we report the preparation of a novel catalyst, water dispersible laurate-stabilized ruthenium(0) nanoclusters from the dimethylamine-borane reduction of ruthenium(III) chloride in sodium laurate solution at room temperature. The ruthenium nanoclusters in average size of 2.6 +/- 1.2 nm were isolated from the solution and well characterized by using TEM, XPS, FTIR, and UV-visible electronic absorption spectroscopy, The water dispersible laurate-stabilized ruthenium(0) nanoclusters were found to be highly active and long-live catalyst with a TOF of 75 mol H(2)/mol Ru.min and TTO value of 5900 mol H(2)/mol Ru in the hydrolysis of ammonia-borane at 25.0 +/- 0.1 degrees C.(C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved

Benzylation of benzene and toluene with benzylchloride over clay-based acid catalysts

The pillared clay catalysts were calcined after in corporation of metal polycation ions with exchangeable cations and water. Friedel-Crafts alkylations of aromatic hydrocarbons were carried out in the presence of clay catalysts originating from bentonite. In these reactions, it has been found that pillared clays have excellent catalytic activity. It was found that iron pillared clay (Fe-PILC) was the more efficient catalyst producing quantitative conversion with greatly reduced amounts of catalysts in short reaction period. Their efficiency is attributed to the higher Fe3+, Cr3+ and Al 3+ contents in the catalysts and pillaring effect. The clays have both Bronsted and Lewis acidities which were determined by pyridine adsorption-desorption and in situ FTIR technique

Water soluble laurate-stabilized rhodium(0) nanoclusters catalyst with unprecedented catalytic lifetime in the hydrolytic dehydrogenation of ammonia-borane

Herein we report, for the first time, the preparation and characterization of water soluble rhodium(0) nanoclusters stabilized by laurate (dodecanoate) anion and their catalytic activity in the hydrolysis of ammonia-borane. The water soluble laurate-stabilized rhodium(0) nanoclusters were prepared from the reduction of rhodium(III) chloride by dimethylamine-borane in solution containing sodium laurate at room temperature. The water soluble laurate-stabilized rhodium(0) nanoclusters in average size of 5.2 +/- 2.7 nm could be isolated from the reaction solution and characterized by using UV-vis, TEM, XPS, XRD and FTIR spectroscopic methods. Catalytic activity of rhodium(0) nanoclusters was tested in the hydrolysis of ammonia-borane. They show exceptional catalytic activity and unprecedented catalytic lifetime in this reaction. They provide a TOF value of 200 mol H-2/mol Rh min and 80,000 turnovers in the hydrolysis of ammonia-borane in air at 25.0 +/- 0.1 degrees C

Room temperature aerobic Suzuki cross-coupling reactions in DMF/water mixture using zeolite confined palladium(0) nanoclusters as efficient and recyclable catalyst

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

Hydrogen liberation from the hydrolytic dehydrogenation of dimethylamine-borane at room temperature by using a novel ruthenium nanocatalyst

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

New route to synthesis of PVP-stabilized palladium(0) nanoclusters and their enhanced catalytic activity in Heck and Suzuki cross-coupling reactions

Herein we report a new method for the synthesis and characterization of PVP-stabilized palladium(0) nanoclusters and their enhanced catalytic activity in Suzuki coupling and Heck reactions of aryl bromides with phenylboronic acid and styrene, respectively, under mild conditions. The PVP-stabilized palladium(0) nanoclusters with a particle size of 4.5 +/- 1.1 nm were prepared using a new method: refluxing a mixture of potassium tetrachloropalladate(II) and PVP in methanol at 80 degrees C for 1 h followed by reduction with sodium borohydride. Palladium(0) nanoclusters prepared in this way were stable in solution for weeks, could be isolated as solid materials and were characterized by TEM, XPS, UV-vis, and XRD techniques. The PVP-stabilized palladium(0) nanoclusters were active catalysts in Heck and Suzuki coupling reactions of arylbromides with styrene and phenylboronic acid affording stilbenes and biphenyls, respectively, in high yield. Recycling experiments showed that PVP-stabilized palladium(0) nanoclusters could be used five times with essentially no loss in activity in the Heck and Suzuki coupling reactions. Copyright (C) 2009 John Wiley & Sons, Ltd

Palladium(0) nanoclusters stabilized by poly(4-styrenesulfonic acid-co-maleic acid) as an effective catalyst for Suzuki-Miyaura cross-coupling reactions in water

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

Transfer hydrogenation of aryl ketones with homogeneous ruthenium catalysts containing diazafluorene ligands

WOS: 000388267500008Novel cationic ruthenium(II) complexes bearing a 4,5-diazafluorene unit and p-cymene as ligands have been synthesised. The complexes were characterised based on elemental analysis and Fourier transform infrared and nuclear magnetic resonance spectroscopies. The synthesised Ru(II) complexes were employed as pre-catalysts for the transfer hydrogenation of aromatic ketones using 2-propanol as both hydrogen source and solvent in the presence of NaOH. All complexes showed high catalytic activity as catalysts in the reduction of substituted acetophenones to corresponding secondary alcohols. The products of catalysis were obtained with conversion rates of between 80 and 99%. Among the seven new complexes investigated, the most efficient catalyst showed turnover frequencies in the range 255-291 h(-1) corresponding to 85 to 97% conversion, respectively. Copyright (C) 2016 John Wiley & Sons, Ltd.Dicle University Science and Technology Application and Research Center (DUBTAM); Dicle University [DUBAP- 13-FF-156, DUBAP-14-FF-75]Analysis and research supported by the Dicle University Science and Technology Application and Research Center (DUBTAM) is gratefully acknowledged. This work was supported by the Research Fund of Dicle University (DUBAP- 13-FF-156 and DUBAP-14-FF-75)