Transition state for intramolecular C-H bond cleavage in [(LCu)2(μ-O)2]2+ (L = 1,4,7-tribenzyl-1,4,7-triazacyclononane)

Christopher J. Cramer, Youngshang Pak

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23 Scopus citations

Abstract

Hybrid quantum mechanical/molecular mechanical electronic structure calculations reveal the transition state for C-H bond cleavage in [(LCu)2 (μ-O)2]2+ (L=1,4,7-tribenzyl-1,4,7-triazacyclononane) to be consistent with a hydrogen-atom-transfer mechanism from carbon to oxygen. At the MPW1K/double-zeta effective core potential( + ) univeral force field level, 0 K activation enthalpies for the parent, p-CF3, and p-OH substituted benzyl systems are predicted to be 8.8, 9.5, and 7.8 kcal/mol. Using a one-dimensional Eckart potential to estimate quantum effects on the reaction coordinate, reaction in the unsubstituted system is predicted to proceed with a primary kinetic isotope effect of 22 at 233 K. Structural parameters associated with the hydrogen-atom transfer are consistent with the Hammond postulate.

Original languageEnglish (US)
Pages (from-to)477-480
Number of pages4
JournalTheoretical Chemistry Accounts
Volume105
Issue number6
DOIs
StatePublished - May 1 2001

Keywords

  • Binuclear copper
  • C-H activation
  • Hydrogen-atom transfer
  • Oxygen activation
  • Tunneling

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