56110-59-9Relevant articles and documents
Branching ratios and bond dissociation energies from the excimer laser photolysis of group 6 metal carbonyls
Rayner, D. M.,Ishikawa, Y.,Brown, C. E.,Hackett, P. A.
, p. 5471 - 5480 (2007/10/02)
Photolysis of the group 6 (Cr, Mo, W) metal carbonyls in the gas phase, at excimer laser wavelengths, may lead to more than one primary product.Branching ratios between these products have been measured as a function of photolysis wavelength, buffer gas pressure, and temperature using time-resolved infrared spectroscopy.The results are modeled using a sequential dissociation mechanism in which branching ratios are determined by competition between unimolecular dissociation and collisional relaxation.The sensitivity of the results to thermochemical input parameters and assumptions concerning energy disposal mechanisms is discussed.Under qualified assumptions the branching ratio measurements provide estimates for CO bond dissociation energies for coordinatively unsaturated metal carbonyls.For Mo and W the individual bond dissociation energies are close to the average values but for Cr the first three ligands coordinated are significantly less strongly bound than the last three.This finding is discussed in terms of recent ab initio calculations on bonding in metal carbonyls.
Photodissociation of Cr(CO)6 in a molecular beam at 248 nm: Observation of primary and secondary photoproducts by mass spectrometry
Tyndall, George W.,Jackson, Robert L.
, p. 2881 - 2891 (2007/10/02)
Photodissociation of Cr(CO)6 induced by a KrF* excimer laser (248 nm) was examined under molecular beam conditions, using a quadrupole mass spectrometer with electron impact ionization (11-19 eV) to detect the products as their respective ions.The ions of all Cr(CO)x products (x=0-5) were produced upon photodissociation of Cr(CO)6 at laser fluences from 1 to 10 mJcm-2.The quantitative behaviour of the Cr(CO)+x product ion yields vs laser fluence as well as statistical rate calculations indicate that Cr(CO)4 is the major product formed upon single-photon dissociation of Cr(CO)6 under collisionless conditions at 248 nm.The additional Cr(CO)+x (x5mJcm-2, secondary photodissociation of Cr(CO)4 becomes important.Cr(CO)2 is assigned as the major photoproduct formed via secondary photodissociation of Cr(CO)4.
Studies on the Photochemistry of Chromium Hexacarbonyl in the Gas Phase: Primary and Secondary Processes
Fletcher, T. Rick,Rosenfeld, Robert N.
, p. 2203 - 2212 (2007/10/02)
The photochemistry of Cr(CO)6, induced by pulsed laser excitation at 249 nm, has been studied with time resolved infrared laser absorption spectroscopy.This method allows us to determine the temporal evolution of the reactant and all major product species.We find that photoactivated Cr(CO)6 decays to yield Cr(CO)5 and CO.The CO product is translationally as well as ro-vibrationally excited.The Cr(CO)5 product is formed with sufficient internal energy to undergo rapid dissociation, yielding Cr(CO)4 and CO.Both decarbonylation reactions occur within 10-7 s of the photoactivation laser pulse.Cr(CO)4 reacts with Cr(CO)6 at a rate of 1.8 (+/-0.3) x 107 torr-1 s-1, yielding Cr2(CO)10.This binuclear complex has a lifetime of at least 10-3 s under our experimental conditions.Cr(CO)4 reacts with CO to form Cr(CO)5 at a rate of 1.4 (+/-0.2) x 106 torr-1 s-1.Cr(CO)5 reacts with CO to form Cr(CO)6 at a rate of 1.2(+/-0.2) x 106 torr-1 s-1.
