Abstract
This paper provides evidence from kinetic experiments and electronic structure calculations of a significantly reduced S-H bond strength in the Mo(μ-SH)Mo function in the homogeneous catalyst model, CpMo(μ-S) 2(μ-SH)2MoCp (1, Cp = η 5-cyclopentadienyl). The reactivity of 1 was explored by determination of a rate expression for hydrogen atom abstraction by benzyl radical from 1 (log(kabs/M-1 s-1) = (9.07 ± 0.38) - (3.62 ± 0.58)/θ) for comparison with expressions for CH3(CH2)7SH, log(kabs/M -1 s-1) = (7.88 ± 0.35) - (4.64 ± 0.54)/θ, and for 2-mercaptonaphthalene, log(kabs/M -1 s-1) = (8.21 ± 0.17) - (4.24 ± 0.26)/θ (θ = 2.303RT kcal/mol, 2σ error). The rate constant for hydrogen atom abstraction at 298 K by benzyl radical from 1 is 2 orders of magnitude greater than that from 1-octanethiol, resulting from the predicted (DFT) S-H bond strength of 1 of 73 kcal/mol. The radical CpMo(μ-S) 3(μ-SH)MoCp, 2, is revealed, from the properties of slow self-reaction, and exclusive cross-combination with reactive benzyl radical, to be a persistent free radical.
| Original language | English |
|---|---|
| Pages (from-to) | 6680-6691 |
| Number of pages | 12 |
| Journal | Journal of the American Chemical Society |
| Volume | 126 |
| Issue number | 21 |
| DOIs | |
| Publication status | Published - Jun 2 2004 |
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ASJC Scopus subject areas
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Activation of the sulfhydryl group by Mo centers : Kinetics of reaction of benzyl radical with a binuclear Mo(μ-SH)Mo complex and with arene and alkane thiols. / Franz, James A.; Birnbaum, Jerome C.; Kolwaite, Douglas S.; Linehan, John; Camaioni, Donald M.; Dupuis, Michel.
In: Journal of the American Chemical Society, Vol. 126, No. 21, 02.06.2004, p. 6680-6691.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Activation of the sulfhydryl group by Mo centers
T2 - Kinetics of reaction of benzyl radical with a binuclear Mo(μ-SH)Mo complex and with arene and alkane thiols
AU - Franz, James A.
AU - Birnbaum, Jerome C.
AU - Kolwaite, Douglas S.
AU - Linehan, John
AU - Camaioni, Donald M.
AU - Dupuis, Michel
PY - 2004/6/2
Y1 - 2004/6/2
N2 - This paper provides evidence from kinetic experiments and electronic structure calculations of a significantly reduced S-H bond strength in the Mo(μ-SH)Mo function in the homogeneous catalyst model, CpMo(μ-S) 2(μ-SH)2MoCp (1, Cp = η 5-cyclopentadienyl). The reactivity of 1 was explored by determination of a rate expression for hydrogen atom abstraction by benzyl radical from 1 (log(kabs/M-1 s-1) = (9.07 ± 0.38) - (3.62 ± 0.58)/θ) for comparison with expressions for CH3(CH2)7SH, log(kabs/M -1 s-1) = (7.88 ± 0.35) - (4.64 ± 0.54)/θ, and for 2-mercaptonaphthalene, log(kabs/M -1 s-1) = (8.21 ± 0.17) - (4.24 ± 0.26)/θ (θ = 2.303RT kcal/mol, 2σ error). The rate constant for hydrogen atom abstraction at 298 K by benzyl radical from 1 is 2 orders of magnitude greater than that from 1-octanethiol, resulting from the predicted (DFT) S-H bond strength of 1 of 73 kcal/mol. The radical CpMo(μ-S) 3(μ-SH)MoCp, 2, is revealed, from the properties of slow self-reaction, and exclusive cross-combination with reactive benzyl radical, to be a persistent free radical.
AB - This paper provides evidence from kinetic experiments and electronic structure calculations of a significantly reduced S-H bond strength in the Mo(μ-SH)Mo function in the homogeneous catalyst model, CpMo(μ-S) 2(μ-SH)2MoCp (1, Cp = η 5-cyclopentadienyl). The reactivity of 1 was explored by determination of a rate expression for hydrogen atom abstraction by benzyl radical from 1 (log(kabs/M-1 s-1) = (9.07 ± 0.38) - (3.62 ± 0.58)/θ) for comparison with expressions for CH3(CH2)7SH, log(kabs/M -1 s-1) = (7.88 ± 0.35) - (4.64 ± 0.54)/θ, and for 2-mercaptonaphthalene, log(kabs/M -1 s-1) = (8.21 ± 0.17) - (4.24 ± 0.26)/θ (θ = 2.303RT kcal/mol, 2σ error). The rate constant for hydrogen atom abstraction at 298 K by benzyl radical from 1 is 2 orders of magnitude greater than that from 1-octanethiol, resulting from the predicted (DFT) S-H bond strength of 1 of 73 kcal/mol. The radical CpMo(μ-S) 3(μ-SH)MoCp, 2, is revealed, from the properties of slow self-reaction, and exclusive cross-combination with reactive benzyl radical, to be a persistent free radical.
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U2 - 10.1021/ja049321r
DO - 10.1021/ja049321r
M3 - Article
VL - 126
SP - 6680
EP - 6691
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 21
ER -