TY - JOUR
T1 - Intramolecular vs. Intermolecular Alkyl C-H Bond Activation. Complete Thermodynamic and Kinetic Parameters for a Reversible Cyclometalation
AU - Smit, Gregory M.
AU - Carpenter, John D.
AU - Marks, Tobin J.
N1 - Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 1986
Y1 - 1986
N2 - Despite the widespread occurrence of intramolecular C-H activating1, 2 cyclometalation processes3(eq 1) and the possibility that they may enjoy an “intramolecular advantage”4, 5 over competing intermolecular processes, relevant comparative thermodynamic (ΔH, AS) and kinetic (ΔH*, ΔS*) information is surprisingly sparse. For one rhodium system, Jones and Feher6 showed that an intramolecular process enjoyed a slight thermodynamic (only AG° could be measured) advantage but also a slight kinetic disadvantage (only in AH*). We recently reported kinetic/mechanistic studies of intermolecular alkane activation7 and closely related intramolecular cyclometalation8 at thorium centers (eq 2–4). C-H scission was found to be rate-limiting, and thermochemical data (ΔH)9suggest that eq 3 and 4 are entropically driven. We now report that the reversibility of eq 4 can be rendered observable, presenting a unique opportunity to quantify, in toto, thermodymamic and kinetic aspects of the in tramolecular cyclometalation process vis-á-vis its intermolecular microscopic reverse.
AB - Despite the widespread occurrence of intramolecular C-H activating1, 2 cyclometalation processes3(eq 1) and the possibility that they may enjoy an “intramolecular advantage”4, 5 over competing intermolecular processes, relevant comparative thermodynamic (ΔH, AS) and kinetic (ΔH*, ΔS*) information is surprisingly sparse. For one rhodium system, Jones and Feher6 showed that an intramolecular process enjoyed a slight thermodynamic (only AG° could be measured) advantage but also a slight kinetic disadvantage (only in AH*). We recently reported kinetic/mechanistic studies of intermolecular alkane activation7 and closely related intramolecular cyclometalation8 at thorium centers (eq 2–4). C-H scission was found to be rate-limiting, and thermochemical data (ΔH)9suggest that eq 3 and 4 are entropically driven. We now report that the reversibility of eq 4 can be rendered observable, presenting a unique opportunity to quantify, in toto, thermodymamic and kinetic aspects of the in tramolecular cyclometalation process vis-á-vis its intermolecular microscopic reverse.
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U2 - 10.1021/ja00281a059
DO - 10.1021/ja00281a059
M3 - Article
AN - SCOPUS:0000087052
VL - 108
SP - 6805
EP - 6807
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 21
ER -