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Pivaloylmetals (tBu-COM: M = Li, MgX, K) as equilibrium components
R Knorr1, G Böhrer, B Schubert
1Department Chemie der Ludwig-Maximilians-Universität, Butenandtstrasse 5-13 (Haus F), 81377 München, Germany. rhk@cup.uni-muenchen.de
Chemistry (Weinheim an Der Bergstrasse, Germany)
|April 17, 2012
Summary
Short-lived pivaloylmetals are reactive intermediates formed from overcrowded metal alkoxides. These intermediates rapidly dimerize or react with ketones, but their overall decay is slow due to competing processes.
Area of Science:
- Organometallic Chemistry
- Reaction Mechanisms
Background:
- Overcrowded metal alkoxides are precursors to reactive intermediates.
- Understanding the reactivity of short-lived organometallic species is crucial for synthetic chemistry.
Purpose of the Study:
- To investigate the formation and reactivity of short-lived pivaloylmetal intermediates.
- To elucidate the mechanisms of dimerization, ketone trapping, and return processes.
Main Methods:
- Thermal decomposition of overcrowded metal alkoxides (MgX, Li, K).
- Trapping experiments using deuterated ketones and other nucleophiles.
- Kinetic analysis to determine reaction rates and pathways.
Main Results:
- Short-lived pivaloylmetals ((H(3)C)(3)C-COM) are generated via thermal heterolytic fission.
- These intermediates undergo rapid dimerization to enediolates or react with ketones.
- A significant return process competes with product formation, leading to slow overall decay rates for Li and K precursors.
Conclusions:
- The reactivity of pivaloylmetal intermediates is complex, involving competing fission, return, and dimerization pathways.
- Kinetic partitioning heavily favors the return process for Li and K intermediates.
- The basicity of the metal influences subsequent reactions, such as protonation.
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