title: Regioselectivity and equilibrium thermodynamics for addition of Rh-OH to olefins in water.
abstract: Rhodium(III) tetra(p-sulfonato phenyl) porphyrin ((TSPP)Rh) aquo and hydroxo complexes react with a series of olefins in water to form beta-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-CH(2)CH(OH)R complexes. Acrylic and styrenic olefins initially react to place rhodium on the terminal carbon to form Rh-CH(2)CH(OH)X as the kinetically preferred isomer but subsequently proceed to an equilibrium distribution of regioisomers where Rh-CH(CH(2)OH)X is the predominant thermodynamic product. Equilibrium constants for reactions of the diaquo rhodium(III) compound ([(TSPP)Rh(III)(H(2)O)(2)](-3)) in water with a series of terminal olefins that form beta-hydroxyalkyl complexes were directly evaluated and used in deriving thermodynamic values for addition of the Rh-OH unit to olefins. The DeltaG degrees 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.
authors.affiliation: Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA.
authors.forename: Xuefeng
authors.initials: X
authors.lastname: Fu
authors.forename: Shan
authors.initials: S
authors.lastname: Li
authors.forename: Bradford B
authors.initials: BB
authors.lastname: Wayland
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D012238:Rhodium / Q000737:chemistry*; D012680:Sensitivity and Specificity; D013237:Stereoisomerism; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
chemical_list: D000475:Alkenes; D009942:Organometallic Compounds; D014867:Water; D012238:Rhodium