Kinetics and mechanism of reversible oxidative addition of hydrogen across the metal - metal bond of (μ-H)2Ru3(CO)8(μ-P)(t-Bu)2)2. Steric promotion of metal - metal bond cleavage but a CO dissociative mechanism

Fred J. Safarowic; David J. Bierdeman; Jerome B. Keister

doi:10.1021/ja9628819

Kinetics and mechanism of reversible oxidative addition of hydrogen across the metal - metal bond of (μ-H)₂Ru₃(CO)₈(μ-P)(t-Bu)₂)₂. Steric promotion of metal - metal bond cleavage but a CO dissociative mechanism

Fred J. Safarowic
, David J. Bierdeman
, Jerome B. Keister

Chemistry

SUNY Buffalo

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

28 Scopus citations

Abstract

The kinetics of the reaction (μ-H)₂Ru₃(CO)₈(μ-P(t-Bu)₂)₂ + H₂ ⇆ (μ-H)₂Ru₃(CO)₈(H)₂(μ-P(t-Bu)₂)₂ have been studied. The reaction of (μ-H)₂Ru₃(CO)₈(μ-P(t-Bu)₂)₂ with H₂ has a rate law which is first-order in cluster concentration and in hydrogen pressure and inverse order in CO pressure; on the basis of the rate law, activation parameters, and deuterium kinetic isotope effect, hydrogen addition is proposed to involve rapid, reversible dissociation of a carbonyl ligand, followed by rate-determining oxidative addition of hydrogen through a three-center transition state at a single metal atom. Loss of hydrogen from (μ-H)₂Ru₃(H)₂(CO)₈(μ-P(t-Bu)₂)₂ also involves reversible loss of a carbonyl, followed by rate-determining reductive elimination of molecular hydrogen. The reaction is highly sensitive to the steric bulk of the phosphido substituents, as (μ-H)₂Ru₃(CO)₈(μ-PR₂)₂, R = cyclohexyl and phenyl, do not react with hydrogen. In addition, the rate of exchange with ¹³CO is much faster for R = t-Bu than for R = cyclohexyl. Based upon the temperature dependence of the equilibrium constant for hydrogenation, the energy for the unbridged Ru-Ru bond of (μ-H)₂Ru₃(CO)₈(μ-P(t-Bu)₂)₂ is estimated to be 47-59 kJ/mol, the low value being attributed to steric strain.

Original language	English
Pages (from-to)	11805-11812
Number of pages	8
Journal	Journal of the American Chemical Society
Volume	118
Issue number	47
DOIs	https://doi.org/10.1021/ja9628819
State	Published - Nov 27 1996

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Safarowic, F. J., Bierdeman, D. J., & Keister, J. B. (1996). Kinetics and mechanism of reversible oxidative addition of hydrogen across the metal - metal bond of (μ-H)₂Ru₃(CO)₈(μ-P)(t-Bu)₂)₂. Steric promotion of metal - metal bond cleavage but a CO dissociative mechanism. Journal of the American Chemical Society, 118(47), 11805-11812. https://doi.org/10.1021/ja9628819

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title = "Kinetics and mechanism of reversible oxidative addition of hydrogen across the metal - metal bond of (μ-H)2Ru3(CO)8(μ-P)(t-Bu)2)2. Steric promotion of metal - metal bond cleavage but a CO dissociative mechanism",

abstract = "The kinetics of the reaction (μ-H)2Ru3(CO)8(μ-P(t-Bu)2)2 + H2 ⇆ (μ-H)2Ru3(CO)8(H)2(μ-P(t-Bu)2)2 have been studied. The reaction of (μ-H)2Ru3(CO)8(μ-P(t-Bu)2)2 with H2 has a rate law which is first-order in cluster concentration and in hydrogen pressure and inverse order in CO pressure; on the basis of the rate law, activation parameters, and deuterium kinetic isotope effect, hydrogen addition is proposed to involve rapid, reversible dissociation of a carbonyl ligand, followed by rate-determining oxidative addition of hydrogen through a three-center transition state at a single metal atom. Loss of hydrogen from (μ-H)2Ru3(H)2(CO)8(μ-P(t-Bu)2)2 also involves reversible loss of a carbonyl, followed by rate-determining reductive elimination of molecular hydrogen. The reaction is highly sensitive to the steric bulk of the phosphido substituents, as (μ-H)2Ru3(CO)8(μ-PR2)2, R = cyclohexyl and phenyl, do not react with hydrogen. In addition, the rate of exchange with 13CO is much faster for R = t-Bu than for R = cyclohexyl. Based upon the temperature dependence of the equilibrium constant for hydrogenation, the energy for the unbridged Ru-Ru bond of (μ-H)2Ru3(CO)8(μ-P(t-Bu)2)2 is estimated to be 47-59 kJ/mol, the low value being attributed to steric strain.",

author = "Safarowic, \{Fred J.\} and Bierdeman, \{David J.\} and Keister, \{Jerome B.\}",

year = "1996",

month = nov,

day = "27",

doi = "10.1021/ja9628819",

language = "English",

volume = "118",

pages = "11805--11812",

journal = "Journal of the American Chemical Society",

issn = "0002-7863",

publisher = "American Chemical Society",

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Safarowic, FJ, Bierdeman, DJ & Keister, JB 1996, 'Kinetics and mechanism of reversible oxidative addition of hydrogen across the metal - metal bond of (μ-H)₂Ru₃(CO)₈(μ-P)(t-Bu)₂)₂. Steric promotion of metal - metal bond cleavage but a CO dissociative mechanism', Journal of the American Chemical Society, vol. 118, no. 47, pp. 11805-11812. https://doi.org/10.1021/ja9628819

Kinetics and mechanism of reversible oxidative addition of hydrogen across the metal - metal bond of (μ-H)₂Ru₃(CO)₈(μ-P)(t-Bu)₂)₂. Steric promotion of metal - metal bond cleavage but a CO dissociative mechanism. / Safarowic, Fred J.; Bierdeman, David J.; Keister, Jerome B.
In: Journal of the American Chemical Society, Vol. 118, No. 47, 27.11.1996, p. 11805-11812.

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

TY - JOUR

T1 - Kinetics and mechanism of reversible oxidative addition of hydrogen across the metal - metal bond of (μ-H)2Ru3(CO)8(μ-P)(t-Bu)2)2. Steric promotion of metal - metal bond cleavage but a CO dissociative mechanism

AU - Safarowic, Fred J.

AU - Bierdeman, David J.

AU - Keister, Jerome B.

PY - 1996/11/27

Y1 - 1996/11/27

N2 - The kinetics of the reaction (μ-H)2Ru3(CO)8(μ-P(t-Bu)2)2 + H2 ⇆ (μ-H)2Ru3(CO)8(H)2(μ-P(t-Bu)2)2 have been studied. The reaction of (μ-H)2Ru3(CO)8(μ-P(t-Bu)2)2 with H2 has a rate law which is first-order in cluster concentration and in hydrogen pressure and inverse order in CO pressure; on the basis of the rate law, activation parameters, and deuterium kinetic isotope effect, hydrogen addition is proposed to involve rapid, reversible dissociation of a carbonyl ligand, followed by rate-determining oxidative addition of hydrogen through a three-center transition state at a single metal atom. Loss of hydrogen from (μ-H)2Ru3(H)2(CO)8(μ-P(t-Bu)2)2 also involves reversible loss of a carbonyl, followed by rate-determining reductive elimination of molecular hydrogen. The reaction is highly sensitive to the steric bulk of the phosphido substituents, as (μ-H)2Ru3(CO)8(μ-PR2)2, R = cyclohexyl and phenyl, do not react with hydrogen. In addition, the rate of exchange with 13CO is much faster for R = t-Bu than for R = cyclohexyl. Based upon the temperature dependence of the equilibrium constant for hydrogenation, the energy for the unbridged Ru-Ru bond of (μ-H)2Ru3(CO)8(μ-P(t-Bu)2)2 is estimated to be 47-59 kJ/mol, the low value being attributed to steric strain.

AB - The kinetics of the reaction (μ-H)2Ru3(CO)8(μ-P(t-Bu)2)2 + H2 ⇆ (μ-H)2Ru3(CO)8(H)2(μ-P(t-Bu)2)2 have been studied. The reaction of (μ-H)2Ru3(CO)8(μ-P(t-Bu)2)2 with H2 has a rate law which is first-order in cluster concentration and in hydrogen pressure and inverse order in CO pressure; on the basis of the rate law, activation parameters, and deuterium kinetic isotope effect, hydrogen addition is proposed to involve rapid, reversible dissociation of a carbonyl ligand, followed by rate-determining oxidative addition of hydrogen through a three-center transition state at a single metal atom. Loss of hydrogen from (μ-H)2Ru3(H)2(CO)8(μ-P(t-Bu)2)2 also involves reversible loss of a carbonyl, followed by rate-determining reductive elimination of molecular hydrogen. The reaction is highly sensitive to the steric bulk of the phosphido substituents, as (μ-H)2Ru3(CO)8(μ-PR2)2, R = cyclohexyl and phenyl, do not react with hydrogen. In addition, the rate of exchange with 13CO is much faster for R = t-Bu than for R = cyclohexyl. Based upon the temperature dependence of the equilibrium constant for hydrogenation, the energy for the unbridged Ru-Ru bond of (μ-H)2Ru3(CO)8(μ-P(t-Bu)2)2 is estimated to be 47-59 kJ/mol, the low value being attributed to steric strain.

UR - https://www.scopus.com/pages/publications/0029958463

U2 - 10.1021/ja9628819

DO - 10.1021/ja9628819

M3 - Article

AN - SCOPUS:0029958463

SN - 0002-7863

VL - 118

SP - 11805

EP - 11812

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

IS - 47