Indirect cooperative effects leading to synergism in bimetallic homogeneous catalysts containing azolates as bridging ligands

Journal Article · Tue Jan 01 00:00:00 EST 1991 · Organometallics; (United States)

DOI:https://doi.org/10.1021/om00047a039· OSTI ID:6106844

Esteruelas, M A; Garcia, M P; Lopez, A M; Oro, L A ^[1]

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1. 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), Vol. 10:1; ISSN 0276-7333
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CYCLOALKENES
HYDROGENATION
RUTHENIUM COMPLEXES
CATALYTIC EFFECTS
CARBONYLATION
CHEMICAL REACTION KINETICS
CYCLOHEXANONE
HOMOGENEOUS CATALYSIS
IRIDIUM COMPLEXES
NMR SPECTRA
PHOSPHINES
REDUCTION
SYNERGISM
ALKENES
CATALYSIS
CHEMICAL REACTIONS
COMPLEXES
HYDROCARBONS
KETONES
KINETICS
ORGANIC COMPOUNDS
PHOSPHORUS COMPOUNDS
REACTION KINETICS
SPECTRA
TRANSITION ELEMENT COMPLEXES
400201* - Chemical & Physicochemical Properties