Record Details

Kinetic and Scanning Transmission Electron Microscopy Investigations on a MCM-41 Supported Cluster Derived Enantioselective Ruthenium Nanocatalyst

DSpace at IIT Bombay

View Archive Info
 
 
Field Value
 
Title Kinetic and Scanning Transmission Electron Microscopy Investigations on a MCM-41 Supported Cluster Derived Enantioselective Ruthenium Nanocatalyst
 
Creator INDRA, A
DOBLE, M
BHADURI, S
LAHIRI, GK
 
Subject ASYMMETRIC HYDROGENATION
HOMOGENEOUS CATALYSIS
ETHYL PYRUVATE
PLATINUM CATALYSTS
CINCHONA ALKALOIDS
REACTION PATHWAYS
SOLID-SURFACES
MODEL SYSTEMS
CARBONYL
NANOPARTICLES
ruthenium carbonyl cluster
functionalized MCM-41
hydrogenation catalyst
asymmetric catalysis
nanocatalyst
kinetic model
 
Description The asymmetric hydrogenation of methyl pyruvate to methyllactate, by cinchonidium functionalized MCM-41 supported [Ru(4)(mu-H)(3)(CO)(12)](-) as the precatalyst has been studied kinetically and by scanning transmission electron microscopy (STEM). Existence of an induction time and two competitive equilibriums are inferred from the time monitored conversion data. Steady state approximation gives a poor fit, but a kinetic model (Eley-Rideal) consisting of a fast equilibrium between methyl pyruvate and the catalyst, a slow one between the catalyst and dihydrogen, and a rate determining reaction between the latter and methyl pyruvate, accurately simulates the time monitored conversion profiles. The model suggests that on increasing the methyl pyruvate concentration there is a change in the stoichiometry of the equilibrium between the. catalyst and the methyl pyruvate. The change in enantioselectivity with time can also be accurately simulated by assuming enantiomeric excess to be proportional to the rate constant for methyl lactate formation. Both kinetic and STEM data strongly suggest that in the fresh catalyst the bare metal cluster framework is retained, and under the catalytic conditions agglomeration of the subnano sized clusters leading to the formation of nanoparticleS of ruthenium is a relatively slow process. A hypothetical enantionface selection mechanism consistent with the empirical rate law, previous reports, and other experimental evidence is proposed.
 
Publisher AMER CHEMICAL SOC
 
Date 2012-06-26T08:46:12Z
2012-06-26T08:46:12Z
2011
 
Type Article
 
Identifier ACS CATALYSIS,1(5)511-518
2155-5435
http://dx.doi.org/10.1021/cs200058q
http://dspace.library.iitb.ac.in/jspui/handle/100/14217
 
Language English