Oxygen atom transfer catalysis: Ligand effects on the key reaction barrier in molybdenum (VI) dioxo systems
Апстракт
Catalytic oxygen atom transfer (OAT), which frequently employs molybdenum oxo species, is an important reaction for both nature and industry. The mechanistic details of oxygen atom transfer from Tp(R)MoO(2)(XPh) to PMe(3) were investigated for R = 3-iPr and 3-Me and X=O and S by density functional theory (DFT) calculations of the enthalpies, free energy with solvent corrections, and natural bond orbital (NBO) analysis. The mechanism for both systems proceeds via rate-determining attack of PMe(3) to form a stable intermediate with a bound OPMe(3) ligand. From this intermediate the reaction proceeds through a substitution involving loss of OPMe(3) and coordination of a single CH(3)CN solvent molecule. The solvent corrected free energy barriers of the rate-determining OAT step for the O and S systems were found to be energetically more favorable for the S systems by 6.2 and 2.2 kcal/mol (for the R=3-iPr and 3-Me, respectively). This lower energy barrier is the result of better stabilizati...on by the SPh ligand of the Mo(IV) products and the transition states, which are the unexpectedly later and more product-like. Additional examination of the NBO analysis emphasizes the role of the local acidity of the Mo and by extension the character of the ligands. The decreased electronegativity and softer character of the S atom result in an increased covalent character in the Mo-X bond which leads to the stabilization of a later (and lower energy) transition state and the corresponding product of the S system relative to O system. (C) 2010 Elsevier B.V. All rights reserved.
Кључне речи:
Oxygen atom transfer (OAT) / Phosphine oxidation / Molybdenum catalysis / Density functional theoryИзвор:
Journal of Molecular Catalysis. A: Chemical, 2010, 324, 1-2, 15-23Финансирање / пројекти:
- National Science Foundation [CHE-0518074, CHE-0541587, CHE-0910552], Welch Foundation [A-0648], Serbian Ministry of Science [142037]
DOI: 10.1016/j.molcata.2010.02.027
ISSN: 1381-1169
WoS: 000278823100004
Scopus: 2-s2.0-77954175841
Колекције
Институција/група
VinčaTY - JOUR AU - Keith, Jason M. AU - Tomić, Zoran D. AU - Zarić, Snežana D. AU - Hall, Michael B. PY - 2010 UR - https://vinar.vin.bg.ac.rs/handle/123456789/4019 AB - Catalytic oxygen atom transfer (OAT), which frequently employs molybdenum oxo species, is an important reaction for both nature and industry. The mechanistic details of oxygen atom transfer from Tp(R)MoO(2)(XPh) to PMe(3) were investigated for R = 3-iPr and 3-Me and X=O and S by density functional theory (DFT) calculations of the enthalpies, free energy with solvent corrections, and natural bond orbital (NBO) analysis. The mechanism for both systems proceeds via rate-determining attack of PMe(3) to form a stable intermediate with a bound OPMe(3) ligand. From this intermediate the reaction proceeds through a substitution involving loss of OPMe(3) and coordination of a single CH(3)CN solvent molecule. The solvent corrected free energy barriers of the rate-determining OAT step for the O and S systems were found to be energetically more favorable for the S systems by 6.2 and 2.2 kcal/mol (for the R=3-iPr and 3-Me, respectively). This lower energy barrier is the result of better stabilization by the SPh ligand of the Mo(IV) products and the transition states, which are the unexpectedly later and more product-like. Additional examination of the NBO analysis emphasizes the role of the local acidity of the Mo and by extension the character of the ligands. The decreased electronegativity and softer character of the S atom result in an increased covalent character in the Mo-X bond which leads to the stabilization of a later (and lower energy) transition state and the corresponding product of the S system relative to O system. (C) 2010 Elsevier B.V. All rights reserved. T2 - Journal of Molecular Catalysis. A: Chemical T1 - Oxygen atom transfer catalysis: Ligand effects on the key reaction barrier in molybdenum (VI) dioxo systems VL - 324 IS - 1-2 SP - 15 EP - 23 DO - 10.1016/j.molcata.2010.02.027 ER -
@article{ author = "Keith, Jason M. and Tomić, Zoran D. and Zarić, Snežana D. and Hall, Michael B.", year = "2010", abstract = "Catalytic oxygen atom transfer (OAT), which frequently employs molybdenum oxo species, is an important reaction for both nature and industry. The mechanistic details of oxygen atom transfer from Tp(R)MoO(2)(XPh) to PMe(3) were investigated for R = 3-iPr and 3-Me and X=O and S by density functional theory (DFT) calculations of the enthalpies, free energy with solvent corrections, and natural bond orbital (NBO) analysis. The mechanism for both systems proceeds via rate-determining attack of PMe(3) to form a stable intermediate with a bound OPMe(3) ligand. From this intermediate the reaction proceeds through a substitution involving loss of OPMe(3) and coordination of a single CH(3)CN solvent molecule. The solvent corrected free energy barriers of the rate-determining OAT step for the O and S systems were found to be energetically more favorable for the S systems by 6.2 and 2.2 kcal/mol (for the R=3-iPr and 3-Me, respectively). This lower energy barrier is the result of better stabilization by the SPh ligand of the Mo(IV) products and the transition states, which are the unexpectedly later and more product-like. Additional examination of the NBO analysis emphasizes the role of the local acidity of the Mo and by extension the character of the ligands. The decreased electronegativity and softer character of the S atom result in an increased covalent character in the Mo-X bond which leads to the stabilization of a later (and lower energy) transition state and the corresponding product of the S system relative to O system. (C) 2010 Elsevier B.V. All rights reserved.", journal = "Journal of Molecular Catalysis. A: Chemical", title = "Oxygen atom transfer catalysis: Ligand effects on the key reaction barrier in molybdenum (VI) dioxo systems", volume = "324", number = "1-2", pages = "15-23", doi = "10.1016/j.molcata.2010.02.027" }
Keith, J. M., Tomić, Z. D., Zarić, S. D.,& Hall, M. B.. (2010). Oxygen atom transfer catalysis: Ligand effects on the key reaction barrier in molybdenum (VI) dioxo systems. in Journal of Molecular Catalysis. A: Chemical, 324(1-2), 15-23. https://doi.org/10.1016/j.molcata.2010.02.027
Keith JM, Tomić ZD, Zarić SD, Hall MB. Oxygen atom transfer catalysis: Ligand effects on the key reaction barrier in molybdenum (VI) dioxo systems. in Journal of Molecular Catalysis. A: Chemical. 2010;324(1-2):15-23. doi:10.1016/j.molcata.2010.02.027 .
Keith, Jason M., Tomić, Zoran D., Zarić, Snežana D., Hall, Michael B., "Oxygen atom transfer catalysis: Ligand effects on the key reaction barrier in molybdenum (VI) dioxo systems" in Journal of Molecular Catalysis. A: Chemical, 324, no. 1-2 (2010):15-23, https://doi.org/10.1016/j.molcata.2010.02.027 . .