Regioselectivity and Equilibrium Thermodynamics for Addition of Rh−OH to Olefins in Water

Xuefeng Fu, Shan Li, and Bradford B. Wayland*
Contribution from the Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323
J. Am. Chem. Soc., 2006, 128 (27), pp 8947–8954
DOI: 10.1021/ja0583416
Publication Date (Web): June 14, 2006
Copyright © 2006 American Chemical Society
*

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

, wayland@sas.upenn.edu

Abstract

Abstract Image

Rhodium(III) tetra(p-sulfonato phenyl) porphyrin ((TSPP)Rh) aquo and hydroxo complexes react with a series of olefins in water to form β-hydroxyalkyl complexes. Addition reactions of (TSPP)Rh−OH to unactivated terminal alkenes invariably occur with both kinetic and thermodynamic preferences to place rhodium on the terminal carbon to form (TSPP)Rh−CH2CH(OH)R complexes. Acrylic and styrenic olefins initially react to place rhodium on the terminal carbon to form Rh−CH2CH(OH)X as the kinetically preferred isomer but subsequently proceed to an equilibrium distribution of regioisomers where Rh−CH(CH2OH)X is the predominant thermodynamic product. Equilibrium constants for reactions of the diaquo rhodium(III) compound ([(TSPP)RhIII(H2O)2]-3) in water with a series of terminal olefins that form β-hydroxyalkyl complexes were directly evaluated and used in deriving thermodynamic values for addition of the Rh−OH unit to olefins. The ΔG° for reactions of the Rh−OH unit with olefins in water is approximately 3 kcal mol-1 less favorable than the comparable Rh−H reactions in water. Comparisons of the regioisomers and thermodynamics for addition reactions of olefins with Rh−H and Rh−OH units in water are presented and discussed.

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History

  • Published In Issue July 12, 2006
  • Received December 8, 2005

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