Energetics of C-H bond activation of fluorinated aromatic hydrocarbons using a [Tp'Rh(CNneopentyl)] complex
Meagan E Evans1, Catherine L Burke, Sornanong Yaibuathes
1Department of Chemistry, University of Rochester, Rochester, New York 14627, USA.
Abstract:
C-H bond activation of fluorinated aromatic hydrocarbons by [Tp'Rh(CNneopentyl)] resulted in the formation of products of the type Tp'Rh(CNneopentyl)(aryl(F))H. The stability of the Rh-C(aryl) product is shown to be strongly dependent on the number of ortho fluorines and only mildly dependent on the total number of fluorine substituents. Complexes with aryl groups containing two ortho fluorines have barriers to reductive elimination that are approximately 5 kcal mol(-1) higher than for those with a single ortho fluorine. Competition experiments along with DeltaG(re)(double dagger) values allow for the determination of relative Rh-C(aryl) bond strengths and illustrate the large ortho fluorine effect on the strength of the Rh-C(aryl) bond. A large change in Rh-C(aryl) bond strength was measured for small changes in the respective calculated C-H bond strengths. Relating M-C to C-H bond strengths resulted in a line (slope = 2.14) that closely matches the theoretically calculated value (slope = 1.96). This is the first experimental quantization of an ortho fluorine effect as predicted by theory.
Related Concept Videos
Aromatic Hydrocarbon Cations: Structural Overview
Removing one hydrogen from the intervening CH2 group with both...
Aromatic Hydrocarbon Anions: Structural Overview
Due to the absence of continuous overlap of p...
Photochemical Electrocyclic Reactions: Stereochemistry
Selection Rules: Photochemical Activation
Thermal and Photochemical Electrocyclic Reactions: Overview
Thermal Electrocyclic Reactions: Stereochemistry
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3


![[(DPEPhos)(bcp)Cu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F59739.jpg&w=3840&q=50)