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 )

Journal Article · Wed Jan 31 04:00:00 EST 1990 · Journal of the American Chemical Society; (USA)

DOI:https://doi.org/10.1021/ja00159a051· OSTI ID:7121485

Jackson, S A; Hodges, P M; Poliakoff, M; Turner, J J ^[1]; Grevels, F ^[2]

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1. Univ. of Nottingham (England)
2. 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), Journal Name: Journal of the American Chemical Society; (USA) Vol. 112:3; ISSN 0002-7863; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104 -- Metals & Alloys-- Physical Properties
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKANES
ALKENES
CARBONYLS
CATALYSIS
CHEMICAL REACTIONS
CHROMIUM
CYCLOALKENES
DATA
DATA ANALYSIS
ELEMENTS
ETHANE
EXPERIMENTAL DATA
HYDROCARBONS
HYDROGEN
HYDROGENATION
INFORMATION
INFRARED SPECTRA
MEASURING INSTRUMENTS
MEASURING METHODS
METALS
MOLYBDENUM
NONMETALS
NORBORNADIENE
NUMERICAL DATA
ORGANIC COMPOUNDS
PHOTOCHEMICAL REACTIONS
SPECTRA
TRANSITION ELEMENTS
TUNGSTEN