Kinetics of molecular hydrogen activation by cobaltrhodium heptacarbonyl

• Published in: Organometallics Vol. 9; no. 6; pp. 1943 - 1949
• Main Authors: Garland, Marc, Pino, Piero
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.06.1990
• Subjects: 400201 - Chemical & Physicochemical Properties; CHEMICAL ACTIVATION; Chemistry; COMPLEXES; DATA; DATA ANALYSIS; ELEMENTS; Exact sciences and technology; EXPERIMENTAL DATA; HYDROGEN; INFORMATION; Inorganic chemistry and origins of life; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; KINETICS; Kinetics and mechanism of reactions; MEASURING INSTRUMENTS; MEASURING METHODS; MEDIUM TEMPERATURE; NONMETALS; NUMERICAL DATA; RHODIUM COMPLEXES; TRANSITION ELEMENT COMPLEXES; Temperature; Medium effect; Hydrogen; Arrhenius equation; Transition metal Carbonyl; Hexane; Activation; Carbon monoxide; Liquid phase; Rate constant; Thermodynamic properties
• DOI: 10.1021/om00156a039
• ISSN: 0276-7333

The kinetics of the activation of molecular hydrogen by the coordinatively unsaturated mixed-metal carbonyl CoRh(CO){sub 7} (1) were studied at temperatures between 276 and 294 K, hydrogen pressures between 0.05 and 0.20 MPa, and carbon monoxide pressures between 0.20 and 0.80 MPa in n-hexane as solvent. The reactions were run under isothermal and isobaric conditions, and the extent of the reaction was followed by high-pressure in situ infrared spectroscopy. The immediately observable products of the activation of molecular hydrogen were HCo(CO){sub 4} (2) and Rh{sub 4}(CO){sub 12} (4), but eventually the dinuclear carbonyl Co{sub 2}(CO){sub 8} (5) began to form via recombination of cobalt carbonyl hydrides. It is concluded on the basis of the orders of reaction that activation occurred through the bimolecular reaction of molecular hydrogen with CoRh(CO){sub 7} without the prior dissociation of a carbonyl ligand.