Structures and energies of main group metal formyl complexes. The mechanism of the reaction of LiH with CO. An ab initio study
Formyl complexes, MCHO, of first- and second-row metals and metal hydrides (M = Li, BeH, BH/sub 2/, Na, MgH, AlH/sub 2/) have been investigated by means of ab initio calculations (MP2/6-31+G*//6-31G* and lower levels). Both eta/sup 2/ (i.e., bridged) and eta/sup 1/ coordination of the metals are found: the former is favored by larger electronegativity differences between the metal and the formyl carbon. Such eta/sup 2/ coordination is characterized by rather long CO bonds, significant alkoxy-carbene character in the formyl group, and a bridging energy of about 5-8 kcal/mol for M = BeH and AlH/sub 2/. The formyl carbon-metal interactions are predominantly ionic. The insertion reaction of CO into the LiH bond, a model for similar processes in transition-metal compounds, proceeds via an initially formed linear coordination complex, HLi-CO, and a three-membered ring transition structure.d The latter lies energetically about 19 kcal/mol above the complex. The overall activation and reaction energies from LiH + CO to the formyllithium product, LiCHO, are +13 and -3 kcal/mol, respectively. The energies of the reaction of the other metal hydrides with CO to form the corresponding formyl compounds are all endothermic by about 1-7 kcal/mol. Thus, with the exception of M = Li, all the formyl complexes, MCHO, are thermodynamically unstable, but they may be observable at lower temperatures if the activation energies for the loss of CO are comparable to that of LiCHO (about 16 kcal/mol).
- Research Organization:
- Friedrich-Alexander-Universitaet, Erlangen-Nuernberg, West Germany
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 6631607
- Journal Information:
- J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 109:9; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ACTIVATION ENERGY
ACYL RADICALS
ALKALI METAL COMPLEXES
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPLEXES
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPLEXES
ALUMINIUM COMPOUNDS
ALUMINIUM HYDRIDES
BERYLLIUM COMPLEXES
BERYLLIUM COMPOUNDS
BERYLLIUM HYDRIDES
BORON COMPLEXES
BORON COMPOUNDS
BORON HYDRIDES
CARBONYLS
CARBOXYLIC ACID SALTS
CHEMICAL REACTIONS
COMPLEXES
CONFIGURATION INTERACTION
DATA
ENERGY
ENERGY LEVELS
FORMYL RADICALS
FUNCTIONS
HYDRIDES
HYDROGEN COMPOUNDS
INFORMATION
LITHIUM COMPLEXES
LITHIUM COMPOUNDS
LITHIUM HYDRIDES
MAGNESIUM COMPLEXES
MAGNESIUM COMPOUNDS
MAGNESIUM HYDRIDES
MOLECULAR STRUCTURE
NUMERICAL DATA
RADICALS
REACTION INTERMEDIATES
SODIUM COMPLEXES
SODIUM COMPOUNDS
SODIUM HYDRIDES
THEORETICAL DATA
THERMODYNAMICS
WAVE FUNCTIONS