Density functional studies on chromium catalyzed ethylene trimerization

Bhaduri, Sumit ; Mukhopadhyay, Sami ; Kulkarni, Sudhir A. (2009) Density functional studies on chromium catalyzed ethylene trimerization Journal of Organometallic Chemistry, 694 (9-10). pp. 1297-1307. ISSN 0022-328X

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Official URL: http://linkinghub.elsevier.com/retrieve/pii/S00223...

Related URL: http://dx.doi.org/10.1016/j.jorganchem.2008.12.012

Abstract

Mechanism of ethylene trimerization using chromium catalyst is investigated using density functional methods. Recent experimental results indicate Cr-based homogeneous catalysts to follow metallacycle pathway in ethylene tri-, teta- and oligomerization reactions. Given the importance of chlorinated Cr-based active catalysts in these reactions, we have used "bare" minimal ligands like Cl- and considered catalytic cycles with neutral or cationic intermediates starting with [Cr(II)Cl2(ethylene)2] and [Cr(II)Cl(ethylene)2]+, respectively. We have compared both 'Cossee' and the 'metallacycle' mechanisms on these model systems utilizing density functional computations at B3LYP/LANL2DZ(d,p) level. The metallacycle mechanism with cationic Cr(II)-Cr(IV) intermediates is found to be the most favored path, with oxidative coupling of two coordinated ethylene to form the chromacyclopentane being the rate determining step (RDS). We also found that with neutral intermediates the Cossee pathway rather than the metallacycle mechanism is followed. Thus in spite of the simplicity of using just Cl- as ligand in the model catalytic intermediates, our computational results match remarkably well with many recent and important experimental findings.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
Keywords:Density Functional; Cationic; Chromium(II)/Chromium(IV) Catalyst; Metallacycle Mechanism; Cossee Mechanism; Ethylene Trimerization
ID Code:2095
Deposited On:08 Oct 2010 09:12
Last Modified:17 Jan 2011 08:42

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