A Theoretical Investigation of the Ni(II)-Catalyzed Hydrovinylation of Styrene

Joseph, Jorly and RajanBabu, TV and Jemmis, Eluvathingal D (2009) A Theoretical Investigation of the Ni(II)-Catalyzed Hydrovinylation of Styrene. In: Organometallics, 28 (12). pp. 3552-3566.

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Abstract

We report a detailed and full computational investigation on the hydrovinylation reaction of styrene with the Ni(II)-phospholane catalytic system, which was originally presumed to proceed through a cationic mechanism involving a nickel hydride intermediate. The following general features emerge from this study on a specific catalyst complex that was found to give quantitative yield and moderate selectivity: (a) the activation barrier for the initiation (18.8 kcal/mol) is higher than that for the reaction due to a low-lying square-planar pentenyl chelate intermediate originating from a Ni(II)-allyl catalyst precursor. Consequently there is an induction period for the catalysis; (b) the exit of product from the catalyst is via a β-H-transfer step instead of the usual β-H elimination pathway, which has a very high activation energy due to a trans effect of the phospholane ligand; (c) the turnover-limiting and enantio- determining transition state is also the β-H-transfer; (d) because of the absence of a hydride intermediate, the unwanted isomerization of the product is prevented; (e) since the enantio-discrimination is decided at the H-transfer stage itself, the configuration of the product in a catalytic cycle influences the enantioselectivity in the subsequent cycle; (f) the trans effect of the sole strong ligand in the d8 square-planar Ni(II), the stability of the η3-benzyl intermediate, and the availability of three coordination sites enable regioselective hydrovinylation over the possible oligomerization/polymerization of the olefin substrates and linear hydrovinylation. This work has also confirmed the previously recognized role of the hemilabile group at various stages in the mechanism.

Item Type:	Journal Article
Publication:	Organometallics
Publisher:	Americal Chemical Society
Additional Information:	Copyrights of this article belongs to Americal Chemical Society.
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	04 Jan 2010 10:26
Last Modified:	19 Sep 2010 05:36
URI:	http://eprints.iisc.ac.in/id/eprint/21325

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