Time-resolved infrared (TRIR) study on the formation and reactivity of organometallic methane and ethane complexes in room temperature solution

Alexander J. Cowan; Peter Portius; Hajime K. Kawanami; Omar S. Jina; David C. Grills; Xue Zhong Sun; Jonathan McMaster; Michael W. George

doi:10.1073/pnas.0610567104

Time-resolved infrared (TRIR) study on the formation and reactivity of organometallic methane and ethane complexes in room temperature solution

Alexander J. Cowan, Peter Portius, Hajime K. Kawanami, Omar S. Jina, David C. Grills, Xue Zhong Sun, Jonathan McMaster, Michael W. George

Research output: Journal Publication › Article › peer-review

53 Citations (Scopus)

Abstract

We have used fast time-resolved infrared spectroscopy to characterize a series of organometallic methane and ethane complexes in solution at room temperature: W(CO)₅(CH₄) and M(η⁵ - C ₅R₅)(CO)₂(L) [where M = Mn or Re, R = H or CH₃ (Re only); and L = CH₄ or C₂H₆]. In all cases, the methane complexes are found to be short-lived and significantly more reactive than the analogous n-heptane complexes. Re(Cp)(CO)₂(CH₄) and Re(Cp*)(CO)₂(L) [Cp* = η⁵ - C₅(CH₃)₅ and L = Ch₄, C₂H₆] were found to be in rapid equilibrium with the alkyl hydride complexes. In the presence of CO, both alkane and alkyl hydride complexes decay at the same rate. We have used picosecond time-resolved infrared spectroscopy to directly monitor the photolysis of Re(Cp*)(CO)₃ in scCH₄ and demonstrated that the initially generated Re(Cp*)(CO)₂(CH₄) forms an equilibrium mixture of Re(Cp*)(CO)₂(CH₄)/ Re(Cp*)(CO)₂(CH₃)H within the first few nanoseconds (τ = 2 ns). The ratio of alkane to alkyl hydride complexes varies in the order Re(Cp)(CO)₂(C₂H₆):Re(Cp)(CO) ₂(C₂H₅)H > Re(Cp*)(CO) ₂(C₂H₆):Re(Cp*)(CO)₂(C ₂H₅)H ≈ Re(Cp)(CO)₂(CH₄):Re(Cp) (CO)₂(CH₃)H > Re(Cp*)(CO)₂(CH ₄):Re(Cp*)(CO)₂(CH₃)H. Activation parameters for the reactions of the organometallic methane and ethane complexes with CO have been measured, and the ΔH^‡ values represent lower limits for the CH₄ binding enthalpies to the metal center of W - CH₄ (30 kJ·mol^-1), Mn - CH₄ (39 kJ·mol^-1), and Re - CH₄ (51 kJ·mol ^-1) bonds in W(CO)₅(CH₄), Mn(Cp)(CO) ₂(CH₄), and Re(Cp)(CO)₂(CH₄), respectively.

Original language	English
Pages (from-to)	6933-6938
Number of pages	6
Journal	Proceedings of the National Academy of Sciences of the United States of America
Volume	104
Issue number	17
DOIs	https://doi.org/10.1073/pnas.0610567104
Publication status	Published - 24 Apr 2007
Externally published	Yes

Keywords

Alkane
Spectroscopy
Supercritical fluid

ASJC Scopus subject areas

General

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10.1073/pnas.0610567104

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Cowan, A. J., Portius, P., Kawanami, H. K., Jina, O. S., Grills, D. C., Sun, X. Z., McMaster, J., & George, M. W. (2007). Time-resolved infrared (TRIR) study on the formation and reactivity of organometallic methane and ethane complexes in room temperature solution. Proceedings of the National Academy of Sciences of the United States of America, 104(17), 6933-6938. https://doi.org/10.1073/pnas.0610567104

@article{99727e00c6ba4a6eaaaf21d66f15f78d,

title = "Time-resolved infrared (TRIR) study on the formation and reactivity of organometallic methane and ethane complexes in room temperature solution",

abstract = "We have used fast time-resolved infrared spectroscopy to characterize a series of organometallic methane and ethane complexes in solution at room temperature: W(CO)5(CH4) and M(η5 - C 5R5)(CO)2(L) [where M = Mn or Re, R = H or CH3 (Re only); and L = CH4 or C2H6]. In all cases, the methane complexes are found to be short-lived and significantly more reactive than the analogous n-heptane complexes. Re(Cp)(CO)2(CH4) and Re(Cp*)(CO)2(L) [Cp* = η5 - C5(CH3)5 and L = Ch4, C2H6] were found to be in rapid equilibrium with the alkyl hydride complexes. In the presence of CO, both alkane and alkyl hydride complexes decay at the same rate. We have used picosecond time-resolved infrared spectroscopy to directly monitor the photolysis of Re(Cp*)(CO)3 in scCH4 and demonstrated that the initially generated Re(Cp*)(CO)2(CH4) forms an equilibrium mixture of Re(Cp*)(CO)2(CH4)/ Re(Cp*)(CO)2(CH3)H within the first few nanoseconds (τ = 2 ns). The ratio of alkane to alkyl hydride complexes varies in the order Re(Cp)(CO)2(C2H6):Re(Cp)(CO) 2(C2H5)H > Re(Cp*)(CO) 2(C2H6):Re(Cp*)(CO)2(C 2H5)H ≈ Re(Cp)(CO)2(CH4):Re(Cp) (CO)2(CH3)H > Re(Cp*)(CO)2(CH 4):Re(Cp*)(CO)2(CH3)H. Activation parameters for the reactions of the organometallic methane and ethane complexes with CO have been measured, and the ΔH‡ values represent lower limits for the CH4 binding enthalpies to the metal center of W - CH4 (30 kJ·mol-1), Mn - CH4 (39 kJ·mol-1), and Re - CH4 (51 kJ·mol -1) bonds in W(CO)5(CH4), Mn(Cp)(CO) 2(CH4), and Re(Cp)(CO)2(CH4), respectively.",

keywords = "Alkane, Spectroscopy, Supercritical fluid",

author = "Cowan, {Alexander J.} and Peter Portius and Kawanami, {Hajime K.} and Jina, {Omar S.} and Grills, {David C.} and Sun, {Xue Zhong} and Jonathan McMaster and George, {Michael W.}",

year = "2007",

month = apr,

day = "24",

doi = "10.1073/pnas.0610567104",

language = "English",

volume = "104",

pages = "6933--6938",

journal = "Proceedings of the National Academy of Sciences of the United States of America",

issn = "0027-8424",

publisher = "National Academy of Sciences",

number = "17",

}

Cowan, AJ, Portius, P, Kawanami, HK, Jina, OS, Grills, DC, Sun, XZ, McMaster, J & George, MW 2007, 'Time-resolved infrared (TRIR) study on the formation and reactivity of organometallic methane and ethane complexes in room temperature solution', Proceedings of the National Academy of Sciences of the United States of America, vol. 104, no. 17, pp. 6933-6938. https://doi.org/10.1073/pnas.0610567104

Time-resolved infrared (TRIR) study on the formation and reactivity of organometallic methane and ethane complexes in room temperature solution. / Cowan, Alexander J.; Portius, Peter; Kawanami, Hajime K. et al.
In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 104, No. 17, 24.04.2007, p. 6933-6938.

Research output: Journal Publication › Article › peer-review

TY - JOUR

T1 - Time-resolved infrared (TRIR) study on the formation and reactivity of organometallic methane and ethane complexes in room temperature solution

AU - Cowan, Alexander J.

AU - Portius, Peter

AU - Kawanami, Hajime K.

AU - Jina, Omar S.

AU - Grills, David C.

AU - Sun, Xue Zhong

AU - McMaster, Jonathan

AU - George, Michael W.

PY - 2007/4/24

Y1 - 2007/4/24

N2 - We have used fast time-resolved infrared spectroscopy to characterize a series of organometallic methane and ethane complexes in solution at room temperature: W(CO)5(CH4) and M(η5 - C 5R5)(CO)2(L) [where M = Mn or Re, R = H or CH3 (Re only); and L = CH4 or C2H6]. In all cases, the methane complexes are found to be short-lived and significantly more reactive than the analogous n-heptane complexes. Re(Cp)(CO)2(CH4) and Re(Cp*)(CO)2(L) [Cp* = η5 - C5(CH3)5 and L = Ch4, C2H6] were found to be in rapid equilibrium with the alkyl hydride complexes. In the presence of CO, both alkane and alkyl hydride complexes decay at the same rate. We have used picosecond time-resolved infrared spectroscopy to directly monitor the photolysis of Re(Cp*)(CO)3 in scCH4 and demonstrated that the initially generated Re(Cp*)(CO)2(CH4) forms an equilibrium mixture of Re(Cp*)(CO)2(CH4)/ Re(Cp*)(CO)2(CH3)H within the first few nanoseconds (τ = 2 ns). The ratio of alkane to alkyl hydride complexes varies in the order Re(Cp)(CO)2(C2H6):Re(Cp)(CO) 2(C2H5)H > Re(Cp*)(CO) 2(C2H6):Re(Cp*)(CO)2(C 2H5)H ≈ Re(Cp)(CO)2(CH4):Re(Cp) (CO)2(CH3)H > Re(Cp*)(CO)2(CH 4):Re(Cp*)(CO)2(CH3)H. Activation parameters for the reactions of the organometallic methane and ethane complexes with CO have been measured, and the ΔH‡ values represent lower limits for the CH4 binding enthalpies to the metal center of W - CH4 (30 kJ·mol-1), Mn - CH4 (39 kJ·mol-1), and Re - CH4 (51 kJ·mol -1) bonds in W(CO)5(CH4), Mn(Cp)(CO) 2(CH4), and Re(Cp)(CO)2(CH4), respectively.

AB - We have used fast time-resolved infrared spectroscopy to characterize a series of organometallic methane and ethane complexes in solution at room temperature: W(CO)5(CH4) and M(η5 - C 5R5)(CO)2(L) [where M = Mn or Re, R = H or CH3 (Re only); and L = CH4 or C2H6]. In all cases, the methane complexes are found to be short-lived and significantly more reactive than the analogous n-heptane complexes. Re(Cp)(CO)2(CH4) and Re(Cp*)(CO)2(L) [Cp* = η5 - C5(CH3)5 and L = Ch4, C2H6] were found to be in rapid equilibrium with the alkyl hydride complexes. In the presence of CO, both alkane and alkyl hydride complexes decay at the same rate. We have used picosecond time-resolved infrared spectroscopy to directly monitor the photolysis of Re(Cp*)(CO)3 in scCH4 and demonstrated that the initially generated Re(Cp*)(CO)2(CH4) forms an equilibrium mixture of Re(Cp*)(CO)2(CH4)/ Re(Cp*)(CO)2(CH3)H within the first few nanoseconds (τ = 2 ns). The ratio of alkane to alkyl hydride complexes varies in the order Re(Cp)(CO)2(C2H6):Re(Cp)(CO) 2(C2H5)H > Re(Cp*)(CO) 2(C2H6):Re(Cp*)(CO)2(C 2H5)H ≈ Re(Cp)(CO)2(CH4):Re(Cp) (CO)2(CH3)H > Re(Cp*)(CO)2(CH 4):Re(Cp*)(CO)2(CH3)H. Activation parameters for the reactions of the organometallic methane and ethane complexes with CO have been measured, and the ΔH‡ values represent lower limits for the CH4 binding enthalpies to the metal center of W - CH4 (30 kJ·mol-1), Mn - CH4 (39 kJ·mol-1), and Re - CH4 (51 kJ·mol -1) bonds in W(CO)5(CH4), Mn(Cp)(CO) 2(CH4), and Re(Cp)(CO)2(CH4), respectively.

KW - Alkane

KW - Spectroscopy

KW - Supercritical fluid

UR - http://www.scopus.com/inward/record.url?scp=34547495209&partnerID=8YFLogxK

U2 - 10.1073/pnas.0610567104

DO - 10.1073/pnas.0610567104

M3 - Article

C2 - 17409190

AN - SCOPUS:34547495209

SN - 0027-8424

VL - 104

SP - 6933

EP - 6938

JO - Proceedings of the National Academy of Sciences of the United States of America

JF - Proceedings of the National Academy of Sciences of the United States of America

IS - 17

ER -

Time-resolved infrared (TRIR) study on the formation and reactivity of organometallic methane and ethane complexes in room temperature solution

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