Infrared spectroscopic studies on the photocatalytic hydrogenation of norbornadiene by group 6 metal carbonyls. 1. The role of H sub 2 and the characterization of nonclassical dihydrogen complexes, (. eta. sup 4 -norbornadiene)M(CO) sub 3 (. eta. sup 2 -H sub 2 )
- Univ. of Nottingham (England)
- Max Planck Institute fuer Strahlenchemie, Muelheim (West Germany)
This paper describes the IR characterization of nonclassical H{sub 2} complexes where ethene or norbornadiene (NBD) is coordinated to the same d{sup 6} metal center as the {sup eta}{sup 2}-H{sub 2} and discusses the role of such complexes in the photocatalytic hydrogenation of NBD by group 6 metal carbonyl compounds. The dihydrogen complexes are generated in solution by the photolysis of alkene and diene carbonyl complexes in the presence of an overpressure of H{sub 2} or D{sub 2}. Photolysis of trans-(C{sub 2}H{sub 4}){sub 2}M(CO){sub 4} (M = Cr, Mo, and W) (1) in liquefied xenon (LXe) doped with H{sub 2} or D{sub 2} at {minus}90{degree}C leads to the formation of mer-(C{sub 2}H{sub 4}){sub 2}M(CO){sub 3}(H{sub 2}) (2) (with trans C{sub 2}H{sub 4} groups) and cis-(C{sub 2}H{sub 4})M(CO){sub 4}(H{sub 2}) (3). These species have been characterized by FTIR, and the v(H-H) IR band of the coordinated {eta}{sup 2}-H{sub 2} has been detected for the W complexes. All of these compounds react thermally with N{sub 2} to yield the corresponding dinitrogen complexes. Fast (microsecond) time-resolved IR (TRIR) is used to identify fac- and mer-(NBD)M(CO){sub 3}(n-hept) as the primary photoproducts of the photolysis of (NBD)M(CO){sub 4} (M = Cr, Mo, and W) in n-heptane at room temperature. Detailed studies with Mo show that these intermediates react stereospecifically with N{sub 2} and H{sub 2} to give fac- and mer-(NBD)Mo(CO){sub 3}(X{sub 2}X{sub 2} - N{sub 2} and H{sub 2}). These species can also be generated in LXe by photolysis of either (NBD)Mo(CO){sub 4} or mer-NBD(Mo(CO){sub 3}(C{sub 2}H{sub 4})). In addition, photolysis of (NBD)M(CO){sub 4} (M = Mo or W) in LXe yields products apparently containing {eta}{sup 2}-NBD, which are not observed in the photolysis at room temperature, probably as a result of differences in temperature and photolysis sources.
- OSTI ID:
- 7121485
- Journal Information:
- Journal of the American Chemical Society; (USA), Vol. 112:3; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
36 MATERIALS SCIENCE
NORBORNADIENE
HYDROGENATION
CARBONYLS
CATALYSIS
CHROMIUM
DATA ANALYSIS
ETHANE
EXPERIMENTAL DATA
HYDROGEN
INFRARED SPECTRA
MEASURING INSTRUMENTS
MEASURING METHODS
METALS
MOLYBDENUM
PHOTOCHEMICAL REACTIONS
TUNGSTEN
ALKANES
ALKENES
CHEMICAL REACTIONS
CYCLOALKENES
DATA
ELEMENTS
HYDROCARBONS
INFORMATION
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
SPECTRA
TRANSITION ELEMENTS
400201* - Chemical & Physicochemical Properties
360104 - Metals & Alloys- Physical Properties