TY  - JOUR
AU  - George, Michael W.
AU  - Hall, Michael B.
AU  - Jina, Omar S.
AU  - Portius, Peter
AU  - Sun, Xue-Zhong
AU  - Towrie, Michael
AU  - Wu, Hong
AU  - Yang, Xinzheng
AU  - Zarić, Snežana D.
PY  - 2010
UR  - https://cherry.chem.bg.ac.rs/handle/123456789/1136
AB  - Fast time-resolved infrared spectroscopic measurements have allowed precise determination of the rates of activation of alkanes by Cp'Rh(CO) (Cp' = eta(5)-C5H5 or eta(5)-C5Me5). We have monitored the kinetics of C-H activation in solution at room temperature and determined how the change in rate of oxidative cleavage varies from methane to decane. The lifetime of CpRh(CO)(alkane) shows a nearly linear behavior with respect to the length of the alkane chain, whereas the related Cp*Rh(CO)(alkane) has clear oscillatory behavior upon changing the alkane. Coupled cluster and density functional theory calculations on these complexes, transition states, and intermediates provide the insight into the mechanism and barriers in order to develop a kinetic simulation of the experimental results. The observed behavior is a subtle interplay between the rates of activation and migration. Unexpectedly, the calculations predict that the most rapid process in these Cp'Rh (CO)(alkane) systems is the 1,3-migration along the alkane chain. The linear behavior in the observed lifetime of CpRh(CO)(alkane) results from a mechanism in which the next most rapid process is the activation of primary C-H bonds (-CH3 groups), while the third key step in this system is 1,2-migration with a slightly slower rate. The oscillatory behavior in the lifetime of Cp*Rh(CO)(alkane) with respect to the alkane's chain length follows from subtle interplay between more rapid migrations and less rapid primary C-H activation, with respect to CpRh(CO)(alkane), especially when the CH3 group is near a gauche turn. This interplay results in the activation being controlled by the percentage of alkane conformers.
PB  - Natl Acad Sciences, Washington
T2  - Proceedings of the National Academy of Sciences of the United States
T1  - Understanding the factors affecting the activation of alkane by Cp ' Rh(CO)(2) (Cp ' = Cp or Cp*)
VL  - 107
IS  - 47
SP  - 20178
EP  - 20183
DO  - 10.1073/pnas.1001249107
ER  - 

@article{
author = "George, Michael W. and Hall, Michael B. and Jina, Omar S. and Portius, Peter and Sun, Xue-Zhong and Towrie, Michael and Wu, Hong and Yang, Xinzheng and Zarić, Snežana D.",
year = "2010",
abstract = "Fast time-resolved infrared spectroscopic measurements have allowed precise determination of the rates of activation of alkanes by Cp'Rh(CO) (Cp' = eta(5)-C5H5 or eta(5)-C5Me5). We have monitored the kinetics of C-H activation in solution at room temperature and determined how the change in rate of oxidative cleavage varies from methane to decane. The lifetime of CpRh(CO)(alkane) shows a nearly linear behavior with respect to the length of the alkane chain, whereas the related Cp*Rh(CO)(alkane) has clear oscillatory behavior upon changing the alkane. Coupled cluster and density functional theory calculations on these complexes, transition states, and intermediates provide the insight into the mechanism and barriers in order to develop a kinetic simulation of the experimental results. The observed behavior is a subtle interplay between the rates of activation and migration. Unexpectedly, the calculations predict that the most rapid process in these Cp'Rh (CO)(alkane) systems is the 1,3-migration along the alkane chain. The linear behavior in the observed lifetime of CpRh(CO)(alkane) results from a mechanism in which the next most rapid process is the activation of primary C-H bonds (-CH3 groups), while the third key step in this system is 1,2-migration with a slightly slower rate. The oscillatory behavior in the lifetime of Cp*Rh(CO)(alkane) with respect to the alkane's chain length follows from subtle interplay between more rapid migrations and less rapid primary C-H activation, with respect to CpRh(CO)(alkane), especially when the CH3 group is near a gauche turn. This interplay results in the activation being controlled by the percentage of alkane conformers.",
publisher = "Natl Acad Sciences, Washington",
journal = "Proceedings of the National Academy of Sciences of the United States",
title = "Understanding the factors affecting the activation of alkane by Cp ' Rh(CO)(2) (Cp ' = Cp or Cp*)",
volume = "107",
number = "47",
pages = "20178-20183",
doi = "10.1073/pnas.1001249107"
}

George, M. W., Hall, M. B., Jina, O. S., Portius, P., Sun, X., Towrie, M., Wu, H., Yang, X.,& Zarić, S. D.. (2010). Understanding the factors affecting the activation of alkane by Cp ' Rh(CO)(2) (Cp ' = Cp or Cp*). in Proceedings of the National Academy of Sciences of the United States
Natl Acad Sciences, Washington., 107(47), 20178-20183.
https://doi.org/10.1073/pnas.1001249107

George MW, Hall MB, Jina OS, Portius P, Sun X, Towrie M, Wu H, Yang X, Zarić SD. Understanding the factors affecting the activation of alkane by Cp ' Rh(CO)(2) (Cp ' = Cp or Cp*). in Proceedings of the National Academy of Sciences of the United States. 2010;107(47):20178-20183.
doi:10.1073/pnas.1001249107 .

George, Michael W., Hall, Michael B., Jina, Omar S., Portius, Peter, Sun, Xue-Zhong, Towrie, Michael, Wu, Hong, Yang, Xinzheng, Zarić, Snežana D., "Understanding the factors affecting the activation of alkane by Cp ' Rh(CO)(2) (Cp ' = Cp or Cp*)" in Proceedings of the National Academy of Sciences of the United States, 107, no. 47 (2010):20178-20183,
https://doi.org/10.1073/pnas.1001249107 . .

TY  - JOUR
AU  - Blake, Alexander J.
AU  - George, Michael W.
AU  - Hall, Michael B.
AU  - McMaster, Jonathan
AU  - Portius, Peter
AU  - Sun, Xue Z.
AU  - Towrie, Michael
AU  - Webster, Charles Edwin
AU  - Wilson, Claire
AU  - Zarić, Snežana D.
PY  - 2008
UR  - https://cherry.chem.bg.ac.rs/handle/123456789/910
AB  - Fast time-resolved infrared (TRIR) experiments and density functional (DFT) calculations have been used to elucidate the complete reaction mechanism between alkanes and photolytically activated hydridotris(pyrazoly-1-yl)boratodicarbonylrhodium. TRIR spectra were obtained after photolysis of Rh(TP4-tBu-3,5-Me)(CO)(2) in n-heptane, n-decane, and cyclohexane and of Rh(Tp(3,5-Me))(CO)(2) in n-heptane and cyclohexane. Initial photolysis produces a coordinatively unsaturated, 16-electron monocarbonyl species that vibrationally relaxes to an intermediate with v(CO) of 1971 cm(-1) in n-heptane solution (species A). DFT calculations on Rh(Tp(3,5-Me))(CO)-RH (RH = C2H6, C6H12) suggest that A is the triplet state of a five-coordinate, square-pyramidal Rh(k(3) -Tp(3,5-Me))(CO)-RH, in which the alkane is weakly bound. Within the first 2 ns, a new transient grew in at 1993 cm(-1) (species B). The calculations show that the observed species B is the singlet state of a four-coordinate Rh(K-2-Tp(3,5-Me))(CO)(RH), in which the alkane is strongly bound and one pyrazolyl ring is rotated, decoordinating one N. The transient due to B grew at the same rate as A partially decayed. However, A did not decay completely, but persisted in equilibrium with B throughout the time up to 2500 ps. The v(CO) bands due to A and B decayed at the same rate as a band at 2026 cm(-1) grew in (tau ca. 29 ns, n-heptane). The latter band can be readily assigned to the final alkyl hydride products, Rh(K-3-Tp(4-tBu-3,5-Me))(CO)R(H) and Rh(K-3-Tp(3,5-Me))(CO)R(H) (species D). The experimental data do not allow the elucidation of which of the two alkane complexes, A or B, is C-H activating, or whether both of the complexes react to form the final product. The calculations suggest that a third intermediate (species Q is the C-H activating species, that is, the final product D is formed from C and not directly from either A or B. Species C is nominally a five-coordinate, square-pyramidal Rh(K-21/2-T-p3,T-5-Me)(CO)(RH) complex with a strongly bound alkane and one pyrazolyl partially decoordinated, but occupying the apical position of the square pyramid. Intermediate C is unobserved, as the calculations predict it possesses the same CO stretching frequency as the parent dicarbonyl. The unobserved species is predicted to lie on the reaction path between A and B and to be in rapid equilibrium with the four-coordinate species B.
PB  - Amer Chemical Soc, Washington
T2  - Organometallics
T1  - Probing the mechanism of carbon-hydrogen bond activation by photochemically generated hydridotris(pyrazolyl)borato carbonyl rhodium complexes: New experimental and theoretical investigations
VL  - 27
IS  - 2
SP  - 189
EP  - 201
DO  - 10.1021/om7008217
ER  - 

@article{
author = "Blake, Alexander J. and George, Michael W. and Hall, Michael B. and McMaster, Jonathan and Portius, Peter and Sun, Xue Z. and Towrie, Michael and Webster, Charles Edwin and Wilson, Claire and Zarić, Snežana D.",
year = "2008",
abstract = "Fast time-resolved infrared (TRIR) experiments and density functional (DFT) calculations have been used to elucidate the complete reaction mechanism between alkanes and photolytically activated hydridotris(pyrazoly-1-yl)boratodicarbonylrhodium. TRIR spectra were obtained after photolysis of Rh(TP4-tBu-3,5-Me)(CO)(2) in n-heptane, n-decane, and cyclohexane and of Rh(Tp(3,5-Me))(CO)(2) in n-heptane and cyclohexane. Initial photolysis produces a coordinatively unsaturated, 16-electron monocarbonyl species that vibrationally relaxes to an intermediate with v(CO) of 1971 cm(-1) in n-heptane solution (species A). DFT calculations on Rh(Tp(3,5-Me))(CO)-RH (RH = C2H6, C6H12) suggest that A is the triplet state of a five-coordinate, square-pyramidal Rh(k(3) -Tp(3,5-Me))(CO)-RH, in which the alkane is weakly bound. Within the first 2 ns, a new transient grew in at 1993 cm(-1) (species B). The calculations show that the observed species B is the singlet state of a four-coordinate Rh(K-2-Tp(3,5-Me))(CO)(RH), in which the alkane is strongly bound and one pyrazolyl ring is rotated, decoordinating one N. The transient due to B grew at the same rate as A partially decayed. However, A did not decay completely, but persisted in equilibrium with B throughout the time up to 2500 ps. The v(CO) bands due to A and B decayed at the same rate as a band at 2026 cm(-1) grew in (tau ca. 29 ns, n-heptane). The latter band can be readily assigned to the final alkyl hydride products, Rh(K-3-Tp(4-tBu-3,5-Me))(CO)R(H) and Rh(K-3-Tp(3,5-Me))(CO)R(H) (species D). The experimental data do not allow the elucidation of which of the two alkane complexes, A or B, is C-H activating, or whether both of the complexes react to form the final product. The calculations suggest that a third intermediate (species Q is the C-H activating species, that is, the final product D is formed from C and not directly from either A or B. Species C is nominally a five-coordinate, square-pyramidal Rh(K-21/2-T-p3,T-5-Me)(CO)(RH) complex with a strongly bound alkane and one pyrazolyl partially decoordinated, but occupying the apical position of the square pyramid. Intermediate C is unobserved, as the calculations predict it possesses the same CO stretching frequency as the parent dicarbonyl. The unobserved species is predicted to lie on the reaction path between A and B and to be in rapid equilibrium with the four-coordinate species B.",
publisher = "Amer Chemical Soc, Washington",
journal = "Organometallics",
title = "Probing the mechanism of carbon-hydrogen bond activation by photochemically generated hydridotris(pyrazolyl)borato carbonyl rhodium complexes: New experimental and theoretical investigations",
volume = "27",
number = "2",
pages = "189-201",
doi = "10.1021/om7008217"
}

Blake, A. J., George, M. W., Hall, M. B., McMaster, J., Portius, P., Sun, X. Z., Towrie, M., Webster, C. E., Wilson, C.,& Zarić, S. D.. (2008). Probing the mechanism of carbon-hydrogen bond activation by photochemically generated hydridotris(pyrazolyl)borato carbonyl rhodium complexes: New experimental and theoretical investigations. in Organometallics
Amer Chemical Soc, Washington., 27(2), 189-201.
https://doi.org/10.1021/om7008217

Blake AJ, George MW, Hall MB, McMaster J, Portius P, Sun XZ, Towrie M, Webster CE, Wilson C, Zarić SD. Probing the mechanism of carbon-hydrogen bond activation by photochemically generated hydridotris(pyrazolyl)borato carbonyl rhodium complexes: New experimental and theoretical investigations. in Organometallics. 2008;27(2):189-201.
doi:10.1021/om7008217 .

Blake, Alexander J., George, Michael W., Hall, Michael B., McMaster, Jonathan, Portius, Peter, Sun, Xue Z., Towrie, Michael, Webster, Charles Edwin, Wilson, Claire, Zarić, Snežana D., "Probing the mechanism of carbon-hydrogen bond activation by photochemically generated hydridotris(pyrazolyl)borato carbonyl rhodium complexes: New experimental and theoretical investigations" in Organometallics, 27, no. 2 (2008):189-201,
https://doi.org/10.1021/om7008217 . .