01741nas a2200181 4500008004100000022001400041245011500055210006900170260007600239300001200315490000700327520100800334653002601342653002701368100002001395700001701415856012701432 2012 eng d a0192-865100aNew approximate method for the stochastic simulation of chemical systems: the representative reaction approach0 aNew approximate method for the stochastic simulation of chemical aCOMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USAbWILEY-BLACKWELLcJAN a276-2850 v333 a

We have developed two new approximate methods for stochastically simulating chemical systems. The methods are based on the idea of representing all the reactions in the chemical system by a single reaction, i.e., by the representative reaction approach (RRA). Discussed in the article are the concepts underlying the new methods along with flowchart with all the steps required for their implementation. It is shown that the two RRA methods {with the reaction \$ 2A \textbackslashrightarrow B \$ as the representative reaction (RR)} perform creditably with regard to accuracy and computational efficiency, in comparison to the exact stochastic simulation algorithm (SSA) developed by Gillespie and are able to successfully reproduce at least the first two moments of the probability distribution of each species in the systems studied. As such, the RRA methods represent a promising new approach for stochastically simulating chemical systems. (C) 2011 Wiley Periodicals, Inc. J Comput Chem, 2012

10aapproximate algorithm10aStochastic simulations1 aKadam, Shantanu1 aVanka, Kumar uhttps://library.ncl.res.in/content/new-approximate-method-stochastic-simulation-chemical-systems-representative-reaction-001734nas a2200217 4500008004100000022001400041245011900055210006900174260007700243300001400320520087400334653002601208653003601234653002801270653001401298653001301312100001901325700002701344700001701371856012801388 2014 eng d a1434-194800aNature of the active site in ziegler-natta olefin polymerization catalysis systems - a computational investigation0 aNature of the active site in zieglernatta olefin polymerization  aBOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANYbWILEY-V C H VERLAG GMBHcOCT a5063-50763 a

Pull quantum chemical calculations with density functional theory (DET) show that a principal role of donors in Ziegler-Nana (ZN) oh-din polymerization catalysts is to coordinate to the metal center at the active sites on the MgCl2 surface. Thereby, the behavior of the catalyst is modulated to favor insertion over termination and, thus, polymerization occurs. This is shown to be true for a range of different donors. The calculations indicate that active sites that feature anionic chloride ligands at the titanium center (the conventional model for the active site) would lead to lower-molecular-weight riolymers. If an -OC2H5 group were present instead of a chloride ligand, the active site would much more effectively produce long chain polymers. Therefore, the current work provides important new insights into the nature of the ZN polymerization process.

10aAlkene polymerization10aDensity functional calculations10aheterogeneous catalysis10aInsertion10aPolymers1 aKumawat, Jugal1 aGupta, Virendra, Kumar1 aVanka, Kumar uhttps://library.ncl.res.in/content/nature-active-site-ziegler-natta-olefin-polymerization-catalysis-systems-computational-001395nas a2200157 4500008004100000022001400041245010000055210006900155260011000224300001400334490000700348520071500355100002401070700001701094856012601111 2014 eng d a1477-922600aNew insights into small molecule activation by acyclic silylenes: a computational investigation0 aNew insights into small molecule activation by acyclic silylenes aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcNOV a2194-22010 v433 a

Recently synthesized acyclic silylenes have the potential to rival transition metal complexes in performing single site small molecule activation, which is significant because of the need to find cheap and green alternatives to transition metal complexes for this important class of reactions. However, the current computational study, a full quantum chemical investigation with density functional theory, demonstrates that undesired side reactions would be competitive in these systems during small molecule activation. The current investigation, in addition to shedding light on this problem, also provides solutions on how the undesired side reactions during small molecule activation can be avoided.

1 aKuriakose, Nishamol1 aVanka, Kumar uhttps://library.ncl.res.in/content/new-insights-small-molecule-activation-acyclic-silylenes-computational-investigation-001989nas a2200205 4500008004100000022001400041245017100055210006900226260000800295300001400303490000700317520119400324100002601518700002801544700002401572700001501596700001701611700002501628856013001653 2024 eng d a2044-475300aNickel-catalyzed tandem conversion of paraformaldehyde : methanol to hydrogen and formate/chemo- and stereoselective hydrogenation of alkynes under neutral conditions0 aNickelcatalyzed tandem conversion of paraformaldehyde methanol t cMAY a2779-27930 v143 a

The development of new catalytic protocols for clean and COx-free hydrogen generation from fundamental feedstocks is always interesting and challenging. Herein, we disclose nickel-catalyzed dihydrogen generation from a mixture of paraformaldehyde-methanol under base-free and activator-free conditions. The dihydrogen generation from this redox combination under neutral, oxidative coupling conditions has been integrated with the hydrogen transfer reactions such as chemo- and stereoselective hydrogenation of alkynes in a tandem manner. This unprecedented strategy provides diverse highly stereoselective olefins with excellent tolerance of reducible functional groups such as ether, silyl ether, aldehyde, keto, ester, nitrile, halides including bromo and iodo groups, and heteroarenes. Additionally, we demonstrated catalytic stereo-interconversion of alkenes under benign conditions. The affordable gram-scale synthesis of some important pharmaceutical bioactive molecules has further enhanced their synthetic value. A tandem dihydrogen generation from a mixture of paraformaldehyde-methanol under base-free conditions followed by semihydrogenation of alkynes is reported.

1 aSubaramanian, Murugan1 aPadhy, Subarna, Sukanya1 aGouda, Chandrakanth1 aDas, Tamal1 aVanka, Kumar1 aBalaraman, Ekambaram uhttps://library.ncl.res.in/content/nickel-catalyzed-tandem-conversion-paraformaldehyde-methanol-hydrogen-and-formatechemo-and02457nas a2200373 4500008004100000022001400041245013800055210006900193260000800262300001100270490000800281520127500289653001201564653001201576653001701588653001801605653001101623653003501634653001801669653001101687100002201698700001901720700002201739700001601761700002801777700002101805700002101826700002601847700001701873700002101890700002001911700002301931856012901954 2026 eng d a0021-951700a(NHC-olefin)-nickel(0) nanoparticles: an efficient and selective catalyst for hydrogenation reactions at low temperature and pressure0 aNHColefinnickel0 nanoparticles an efficient and selective cataly cJAN a1164870 v4533 a

The reduction of a NHC-cinnamyl nickel(II) organometallic complex through the use of different MeMgBr or MeMgCl reagents led to two types of NHC-olefin-coordinated nickel nanoparticles. Both of these unsupported nickel-NHC based nanomaterials behaved under hydrogen pressure as effective and selective catalysts operating at low temperature (<= 80 degrees C), pressure (<= 20 bar) and loading (<= 6 mol%) for the reductions of broad scopes of alkenes, alkynes, imines and heterocycles, including a challenging tetra-substituted alkene. Among these two nickel-NHC nanocatalysts, the one generated with MeMgCl showed a significant high catalytic activity with high yields and could stand the comparison with Raney nickel and state-of-the-art nickel nanocatalysts. For example, by studying the hydrogenation of 1-phenylcyclohexene in ethanol at 60 degrees C under 10 bar of H2, 3 mol% of this catalyst achieved the reaction within a single hour on a 5 mmol/0.8 g substrate scale with a yield of 96 %, a turnover number (TON) of 32 and a turnover frequency (TOF) of 32. Characterizations confirmed the coordination of the NHC-olefin ligands to the nickel nanoparticles, the reduced state of the nickel and the (poly-) crystallinity of the nanoparticles.

10aalkenes10aAlkynes10aheterocycles10aHydrogenation10aimines10aN -heterocyclic carbene ligand10ananocatalysis10aNickel1 aAvello, Marta, G.1 aSingh, Geetika1 aTruong-Phuoc, Lai1 aVidal, Loic1 aPapaefthimiou, Vasiliki1 aChesse, Matthieu1 aGruber, Nathalie1 aChetcuti, Michael, J.1 aVanka, Kumar1 aRitleng, Vincent1 aPham-Huu, Cuong1 aMichon, Christophe uhttps://library.ncl.res.in/content/nhc-olefin-nickel0-nanoparticles-efficient-and-selective-catalyst-hydrogenation-reactions