Ionic hydrogenations of hindered olefins at low temperature. Hydride transfer reactions of transition metal hydrides
- Brookhaven National Lab., Upton, NY (United States)
Sterically hindered olefins can be hydrogenated at -50[degree]C in dichloromethane using triflic acid (CF[sub 3]SO[sub 3]H) and a hydride donor. Mechanistic studies indicate that these reactions proceed by hydride transfer to the carbenium ion that is formed by protonation of the olefin. Olefins that form tertiary carbenium ions upon protonation are hydrogenated in high yields (90-100%). Styrenes generally produce lower yields of hydrogenated products (50-60%). Suitable hydride donors include HSiE[sub 3] and several transition metal carbonyl hydrides HW(CO)[sub 3]Cp, HW(CO)[sub 3]Cp[sup +], HMo-(CO)[sub 3]Cp, HMn(CO)[sub 5], HRe(CO)[sub 3], and HO[sub 3](CO)[sub 1]Cp*; Cp = [eta][sup 5]-C[sub 3]H[sub 5+], Cp* = [eta][sup 5]-C[sub 5]Me[sub 5]. A characteristic that is required for transition metal hydrides to be effective is that the cationic dihydrides (or dihydrogen complexes) that result from their protonation must have sufficient acidity to transfer a proton to the olefin, as well as sufficient thermal stability to avoid significant decomposition on the time scale of the hydrogenation reaction. Metal hydrides that fall due to insufficient stability of their protonated forms include HMo(CO)[sub 2](PPH[sub 3])Cp, HMo(CO)[sub 3]Cp*, and HFe(CO)[sub 2]Cp*. 62 refs., 2 tabs.
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 6908818
- Journal Information:
- Journal of the American Chemical Society; (United States), Vol. 116:19; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALKENES
HYDROGENATION
CHEMICAL BONDS
DEUTERIUM COMPOUNDS
HYDRIDES
IRON COMPLEXES
MANGANESE COMPLEXES
METHYLENE CHLORIDE
MOLYBDENUM COMPLEXES
NUCLEAR MAGNETIC RESONANCE
ORGANOMETALLIC COMPOUNDS
OSMIUM COMPLEXES
RHENIUM COMPLEXES
RUTHENIUM COMPLEXES
STYRENE
TUNGSTEN COMPLEXES
ALKYLATED AROMATICS
AROMATICS
CHEMICAL REACTIONS
COMPLEXES
HYDROCARBONS
HYDROGEN COMPOUNDS
MAGNETIC RESONANCE
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
RESONANCE
TRANSITION ELEMENT COMPLEXES
400201* - Chemical & Physicochemical Properties
400102 - Chemical & Spectral Procedures