Abstract
With metal-based catalysts, it is quite common that a ligand (L) must first dissociate from a catalyst precursor (L′nM£L) to activate the catalyst. The resulting coordinatively unsaturated active species (L′nM) can either back react with the ligand in a k-1 step, or combine with the substrate in a k2 step. When dissociation is not rate determining and k-1[L] is greater than or comparable to k2[substrate], this slows the rate of reaction. By introducing a phase label onto the ligand L and providing a suitable orthogonal liquid or solid phase, dramatic rate accelerations can be achieved. This phenomenon is termed "phase-transfer activation". In this Concept, some historical antecedents are reviewed, followed by successful applications involving fluorous/organic and aqueous/organic liquid/liquid biphasic catalysis, and liquid/solid biphasic catalysis. Variants that include a chemical trap for the phase-labeled ligands are also described.
Original language | English |
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Pages (from-to) | 15894-15906 |
Number of pages | 13 |
Journal | Chemistry - A European Journal |
Volume | 21 |
Issue number | 45 |
DOIs | |
Publication status | Published - 1 Nov 2015 |
Externally published | Yes |
Keywords
- biphasic catalysis
- fluorous solvents
- olefin metathesis
- phase transfer
- polymerization