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Title: Kinetic and Mechanistic Studies of the Reactions of Transitions Metal-Activated Oxygen with Inorganic Substrates


No abstract prepared.

Publication Date:
Research Org.:
Ames Laboratory (AMES), Ames, IA
Sponsoring Org.:
USDOE Office of Science and Technology (OST) - (EM-50)
OSTI Identifier:
Report Number(s):
IS-J 7083
Journal ID: ISSN 0010-8545; CCHRAM; TRN: US200621%%723
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Coordination Chemistry Reviews; Journal Volume: 250
Country of Publication:
United States

Citation Formats

Andreja Bakac. Kinetic and Mechanistic Studies of the Reactions of Transitions Metal-Activated Oxygen with Inorganic Substrates. United States: N. p., 2006. Web. doi:10.1016/j.ccr.2006.02.001.
Andreja Bakac. Kinetic and Mechanistic Studies of the Reactions of Transitions Metal-Activated Oxygen with Inorganic Substrates. United States. doi:10.1016/j.ccr.2006.02.001.
Andreja Bakac. Fri . "Kinetic and Mechanistic Studies of the Reactions of Transitions Metal-Activated Oxygen with Inorganic Substrates". United States. doi:10.1016/j.ccr.2006.02.001.
title = {Kinetic and Mechanistic Studies of the Reactions of Transitions Metal-Activated Oxygen with Inorganic Substrates},
author = {Andreja Bakac},
abstractNote = {No abstract prepared.},
doi = {10.1016/j.ccr.2006.02.001},
journal = {Coordination Chemistry Reviews},
number = ,
volume = 250,
place = {United States},
year = {Fri Mar 10 00:00:00 EST 2006},
month = {Fri Mar 10 00:00:00 EST 2006}
  • A series of complexes of vanadocene or molybdenocene with unsymmetrical ketenes were prepared, either by reaction of the various ketenes with vanadocene itself or by reaction with the molybdenocene phosphine complex (C/sub 5/H/sub 5/)/sub 2/Mo(PEt/sub 3/). All of the complexes exhibited the expected ketene C=O bonding mode, and all reactions were very specific in their formation of the facial isomer with metallocene fragment located on the side of the smaller ketene substituent. Kinetic studies were used to assess the sensitivity of the incoming vanadocene to steric and electronic effects, with the latter found to dominate. Kinetic studies and activation parametersmore » for reaction of Cp/sub 2/Mo(PEt/sub 3/) with EtPhC=C=O indicated a second-order associative mechanism, proposed to involve a nucleophilic attack of the metal center on the ketene central carbon in the rate-limiting step. Lastly, reactions of the bound ketenes with nucleophiles (alkyllithiums or Grignard reagents) proceeded readily to either ketone or aldehyde enolates (the latter via transfer of a ..beta..-hydride from the alkyl); the clean production of only Z enolates from the unsymmetrical ketenes is indicate of a metal-mediated internal attack of nucleophile on the bound ketene.« less
  • The reactions of [Pt(triphos)(Cl)][Cl] (1) [C@triphos = bis[2-(diphenylphosphino)ethyl]phenylphosphine] with NaOC{sub 6}H{sub 4}-p-R, in the presence of NaPF{sub 6}, yields the aryloxy complexes [Pt(triphos)(OC{sub 6}H{sub 4}-p-R)][PF{sub 6}] (R = OMe (2a), Me (2b), H (2c), F (2d), Cl (2e)). Upon reaction of 2a-e with carbon monoxide at pressures from 10 to 134 psi in acetonitrile the (aryloxy)carbonyl complexes [Pt(triphos)(C(O)OC{sub 6}H{sub 4}-p-R)][PF{sub 6}] (3a-e) were obtained. The molecular structure of [Pt(triphos)(C(O)OC{sub 6}H{sub 4}-p-Me)][PF{sub 6}] (3b) was determined by X-ray diffraction. Complex 3b crystallized in the monoclinic space group P2{sub 1}n (no. 14). The kinetics of the carbonylation of 2a-e to form 3a-emore » were studied by {sub 31}P[C{sub 1}H] NMR. Rates of carbonylation exhibit a first order dependence on [CO], but are independent of the concentration of free aryloxide in solution. Rates of aryloxide ligand exchange were also found to be significantly faster than rates of carbonylation. The rates of carbonylation depend on the para-substituent of the aryloxy ligand and follow the order F(2d) > Me (2b) > OMe (2a). These observations are interpreted in terms of a carbonylation mechanism that proceeds via a migratory insertion pathway, rather than by nucleophilic attack at coordinated carbon monoxide by free or dissociated aryloxide. 54 refs., 5 figs., 5 tabs.« less
  • A reverse-geometry mass spectrometer is used to obtain product ion kinetic energy release distributions to probe the energetics and mechanisms of several gas-phase organometallic reactions. In particular, we examine the mechanism for C{sub 2}H{sub 4} and C{sub 3}H{sub 6} elimination from Co(cyclopentane){sup +}. The kinetic energy release distribution associated with these processes can be modeled by using phase space calculations assuming, for the C{sub 3}H{sub 6} elimination process, propene rather than cyclopropane is being eliminated as the product neutral, and for the C{sub 2}H{sub 4} elimination process, Co(propene){sup +} rather than (cobaltacyclobutane){sup +} is being formed as the product ion.more » In addition, we obtain a heat of formation for the cobalt ethylene ion of 255 kcal/mol at 0 K, corresponding to a bond dissociation energy of 42 kcal/mol at 0 K, by fitting the theoretical results to the experimental distribution.« less
  • Data are presented that demonstrate that the polyoxoanion-supported Ir(I) precatalyst, (Bu{sub 4}N){sub 5}((1,5-COD)Ir {times} P{sub 2}W{sub 15}Nb{sub 3}O{sub 62}) (I) leads to an active and long-lived catalyst in a phototypical catalytic reaction, olefin hydrogenation. Initial kinetic and mechanistic data are also reported that provide evidence that the actual catalyst derived from I is indeed polyoxoanion supported. 14 refs., 1 fig.
  • We have investigated the kinetics of novel carbon-to-metal hydrogen atom transfer reactions, in which homolytic cleavage of a C-H bond is accomplished by a single metal-centered radical. Studies by means of time-resolved IR spectroscopic measurements revealed efficient hydrogen atom transfer from xanthene, 9,10-dihydroanthracene and 1,4-cyclohexadiene to Cp(CO)2Os• and (n5-iPr4C5H)(CO)2Os• radicals, formed by photoinduced homolysis of the corresponding osmium dimers. The rate constants for hydrogen abstraction from these hydrocarbons were found to be in the range 1.54 × 105 M 1 s 1 -1.73 × 107 M 1 s-1 at 25 °C. For the first time, kinetic isotope effects for carbon-to-metalmore » hydrogen atom transfer were determined. Large primary kinetic isotope effects of 13.4 ± 1.0 and 16.6 ± 1.4 were observed for the hydrogen abstraction from xanthene to form Cp(CO)2OsH and (n5-iPr4C5H)(CO)2OsH, respectively, at 25 °C. Temperature-dependent measurements of the kinetic isotope effects over a 60 -C temperature range were carried out to obtain the difference in activation energies and the pre-exponential factor ratio. For hydrogen atom transfer from xanthene to (n5-iPr4C5H)(CO)2Os•, the (ED - EH) = 3.25 ± 0.20 kcal/mol and AH/AD = 0.056 ± 0.018 values are greater than the semi-classical limits and thus suggest a quantum mechanical tunneling mechanism. The work at BNL was carried out under contract DE-AC02-98CH10886 with the U.S. Department of Energy and supported by its Division of Chemical Sciences, Geosciences & Biosciences, Office of Basic Energy Sciences. RMB also thanks the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences for support. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.« less