Indirect cooperative effects leading to synergism in bimetallic homogeneous catalysts containing azolates as bridging ligands
- Univ. de Zaragoza-Consejo Superior de Investigaciones Cientificas (Spain)
The binuclear compounds (H(CO)(PPh{sub 3}){sub 2}Ru({mu}-bim)Ir(COD)) (1) (bim = 2,2{prime}-biimidazolate, COD = 1,5-cyclooctadiene) and (H(CO)(PPh{sub 3}){sub 2}Ru({mu}-pz){sub 2}Ir(TFB)) (2) (pz = pyrazolate, TFB = tetrafluorobenzobarrelene) are more active catalysts for the hydrogenation of cyclohexene than the mononuclear parent compounds (RuH(Hbim)(CO)(PPh{sub 3}){sub 2}), (Ir(Hbim)(COD)), (RuH(pa)(CO)(Hpz)(PPh{sub 3}){sub 2}), and (Ir(TFB)(Hpz){sub 2})BF{sub 4}. In the presence of 1, the reaction rate is first order with respect to the concentration of 1 and cyclohexene, second order with respect to hydrogen pressure, and inversely proportional to the concentration of added phosphine. For the reaction catalyzed by 2, the experimental data are in accordance with a rate expression of the form {minus}d(cyclohexene)/dt = k(2)(cyclohexene)P(H{sub 2}) (P(H{sub 2}) = hydrogen pressure). On the basis of the kinetic results and experimental evidence, the origin of the catalytic synergism is assigned to indirect cooperative effects between the metallic centers of the binuclear complexes. The kinetic investigation of the hydrogenation of cyclohexene catalyzed by (Ir({mu}-pz)(TFB)){sub 2} (3) is also reported, suggesting that the full catalytic cycle involves binuclear species.
- OSTI ID:
- 6106844
- Journal Information:
- Organometallics; (United States), Journal Name: Organometallics; (United States) Vol. 10:1; ISSN 0276-7333; ISSN ORGND
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
ALKENES
CARBONYLATION
CATALYSIS
CATALYTIC EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COMPLEXES
CYCLOALKENES
CYCLOHEXANONE
HOMOGENEOUS CATALYSIS
HYDROCARBONS
HYDROGENATION
IRIDIUM COMPLEXES
KETONES
KINETICS
NMR SPECTRA
ORGANIC COMPOUNDS
PHOSPHINES
PHOSPHORUS COMPOUNDS
REACTION KINETICS
REDUCTION
RUTHENIUM COMPLEXES
SPECTRA
SYNERGISM
TRANSITION ELEMENT COMPLEXES