Activation of the water molecule. V. Rhodium(I) hydride catalyzed water gas shift reaction. Identification of the elemental reactions comprising the catalytic cycles

Journal Article · Wed Jun 17 04:00:00 EDT 1981 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00402a027· OSTI ID:6217303

Yoshida, T; Okano, T; Ueda, Y; Otsuka, S

Rhodium(I)-hydrido compounds serve as catalyst precursors for the water gas shift (wgs) reaction active under relatively mild conditions (> 50/sup 0/C). The key intermediates appear to be trans-RhH(CO)L/sub 2/ (L = P(i-Pr)/sub 3/) and trans-Rh(OH)(CO)L/sub 2/ (L = P(c-C/sub 6/H/sub 11/)/sub 3/) which in pyridine is in equilibrium with the solvated form (trans-Rh(CO)(py)L/sub 2/)OH (L = P(i-Pr)/sub 3/; L = P(c-C/sub 6/H/sub 11/)/sub 3/). The formation of the solvated forms was shown to proceed through oxidative addition of H/sub 2/O to give (RhH/sub 2/(py)/sub 2/L/sub 2/)OH (step 1) and subsequent reaction of the adduct with CO releasing H/sub 2/ (step 2). H/sub 2/ evolution from the water adduct (RhH/sub 2/(PEt/sub 3/)/sub 3/)OH requires more drastic conditions (80/sup 0/C) and takes place through an intermediate (RhH/sub 2/(CO)(PEt/sub 3/)/sub 3/)/sup +/. Alternatively, the catalyst precursors may react first with CO to give a Rh(0) compound such as Rh/sub 2/(CO)/sub 3/(P(i-Pr)/sub 3/)/sub 3/ and Rh/sub 2/(CO)/sub 4/L/sub 2/ (step 3). Then, these carbonyl compounds react with H/sub 2/O with concomitant evolution of H/sub 2/ (step 4). Under a CO atmosphere trans-RhH(CO)L/sub 2/ is produced through a nucleophilic attack of OH/sup -/ to the coordinated CO to give Rh(CO/sub 2/H)(CO)L/sub 2/ as a transient species (step 5), followed by decarboxylation (step 6). As the wgs reaction proceeds, another cycle becomes important. The cycle is comprised of the reaction with CO/sub 2/-H/sub 2/O to give Rh(OCO/sub 2/H)(CO)(P(i-Pr)/sub 3/)/sub 2/ and H/sub 2/ (step 7), transformation into Rh/sub 2/(..mu..-OCO/sub 2/)(CO)/sub 2/(P(i-Pr)/sub 3/)/sub 4/ (step 8), and hydrolysis.

• Research Organization: Osaka Univ., Japan
• OSTI ID: 6217303
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 103:12; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

08 HYDROGEN
080104* -- Hydrogen-- Production-- Water Gas Processes
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYSIS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
COMPLEXES
DATA
EXPERIMENTAL DATA
HYDROGEN PRODUCTION
INFORMATION
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
RHODIUM COMPLEXES
TRANSITION ELEMENT COMPLEXES
WATER GAS PROCESSES