The rate and mechanism of oxidative addition of H2 to the ·Cr(CO)3C5Me5 radical - Generation of a model for reaction of H2 with the ·Co(CO)4 radical

Kenneth B. Capps; Andreas Bauer; Gabor Kiss; Carl D. Hoff

doi:10.1016/S0022-328X(99)00194-1

The rate and mechanism of oxidative addition of H₂ to the ·Cr(CO)₃C₅Me₅ radical - Generation of a model for reaction of H₂ with the ·Co(CO)₄ radical

Kenneth B. Capps, Andreas Bauer, Gabor Kiss, Carl D. Hoff

Chemistry

Research output: Contribution to journal › Article › peer-review

23 Scopus citations

Abstract

The rate of reaction of hydrogen with the 17 e^- metal centered radical ·Cr(CO)₃C₅Me₅ obeys the third-order rate law d[P]/dt=k_obs[·Cr]²[H₂] in toluene solution. In the temperature range 20-60°C, k_obs=330±30 M^-2 s^-1, ΔH^≠=0±1 kcal mol^-1, ΔS^≠=-47±3 cal mol^-1 deg^-1. The rate of oxidative addition is not inhibited by added pressure of CO. The rate of binding of D₂ is slower than that of H₂: k(H₂)/k(D₂)=1.18. These results are combined with earlier work to generate a complete reaction profile for hydrogenation of the metal-metal bonded dimer [Cr(CO)₃C₅Me₅]₂+H ₂→2H-Cr(CO)₃C₅Me₅. A similar reaction profile for Co₂(CO)₈+H₂→2H-Co(CO)₄ under high pressures of CO is constructed based on literature data and estimated activation parameters for reaction of the ·Co(CO)₄ radical with hydrogen.

Original language	English (US)
Pages (from-to)	23-30
Number of pages	8
Journal	Journal of Organometallic Chemistry
Volume	586
Issue number	1
DOIs	https://doi.org/10.1016/S0022-328X(99)00194-1
State	Published - Jul 31 1999

Keywords

Chromium
Cobalt
Free radicals
Hydrogen
Oxidative addition

ASJC Scopus subject areas

Biochemistry
Inorganic Chemistry
Organic Chemistry
Physical and Theoretical Chemistry
Materials Chemistry

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10.1016/S0022-328X(99)00194-1

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title = "The rate and mechanism of oxidative addition of H2 to the ·Cr(CO)3C5Me5 radical - Generation of a model for reaction of H2 with the ·Co(CO)4 radical",

abstract = "The rate of reaction of hydrogen with the 17 e- metal centered radical ·Cr(CO)3C5Me5 obeys the third-order rate law d[P]/dt=kobs[·Cr]2[H2] in toluene solution. In the temperature range 20-60°C, kobs=330±30 M-2 s-1, ΔH≠=0±1 kcal mol-1, ΔS≠=-47±3 cal mol-1 deg-1. The rate of oxidative addition is not inhibited by added pressure of CO. The rate of binding of D2 is slower than that of H2: k(H2)/k(D2)=1.18. These results are combined with earlier work to generate a complete reaction profile for hydrogenation of the metal-metal bonded dimer [Cr(CO)3C5Me5]2+H 2→2H-Cr(CO)3C5Me5. A similar reaction profile for Co2(CO)8+H2→2H-Co(CO)4 under high pressures of CO is constructed based on literature data and estimated activation parameters for reaction of the ·Co(CO)4 radical with hydrogen.",

keywords = "Chromium, Cobalt, Free radicals, Hydrogen, Oxidative addition",

author = "Capps, {Kenneth B.} and Andreas Bauer and Gabor Kiss and Hoff, {Carl D.}",

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T1 - The rate and mechanism of oxidative addition of H2 to the ·Cr(CO)3C5Me5 radical - Generation of a model for reaction of H2 with the ·Co(CO)4 radical

AU - Capps, Kenneth B.

AU - Bauer, Andreas

AU - Kiss, Gabor

AU - Hoff, Carl D.

PY - 1999/7/31

Y1 - 1999/7/31

N2 - The rate of reaction of hydrogen with the 17 e- metal centered radical ·Cr(CO)3C5Me5 obeys the third-order rate law d[P]/dt=kobs[·Cr]2[H2] in toluene solution. In the temperature range 20-60°C, kobs=330±30 M-2 s-1, ΔH≠=0±1 kcal mol-1, ΔS≠=-47±3 cal mol-1 deg-1. The rate of oxidative addition is not inhibited by added pressure of CO. The rate of binding of D2 is slower than that of H2: k(H2)/k(D2)=1.18. These results are combined with earlier work to generate a complete reaction profile for hydrogenation of the metal-metal bonded dimer [Cr(CO)3C5Me5]2+H 2→2H-Cr(CO)3C5Me5. A similar reaction profile for Co2(CO)8+H2→2H-Co(CO)4 under high pressures of CO is constructed based on literature data and estimated activation parameters for reaction of the ·Co(CO)4 radical with hydrogen.

AB - The rate of reaction of hydrogen with the 17 e- metal centered radical ·Cr(CO)3C5Me5 obeys the third-order rate law d[P]/dt=kobs[·Cr]2[H2] in toluene solution. In the temperature range 20-60°C, kobs=330±30 M-2 s-1, ΔH≠=0±1 kcal mol-1, ΔS≠=-47±3 cal mol-1 deg-1. The rate of oxidative addition is not inhibited by added pressure of CO. The rate of binding of D2 is slower than that of H2: k(H2)/k(D2)=1.18. These results are combined with earlier work to generate a complete reaction profile for hydrogenation of the metal-metal bonded dimer [Cr(CO)3C5Me5]2+H 2→2H-Cr(CO)3C5Me5. A similar reaction profile for Co2(CO)8+H2→2H-Co(CO)4 under high pressures of CO is constructed based on literature data and estimated activation parameters for reaction of the ·Co(CO)4 radical with hydrogen.

KW - Chromium

KW - Cobalt

KW - Free radicals

KW - Hydrogen

KW - Oxidative addition

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