Phase‐Transfer Activation of Transition Metal Catalysts. Issue 45 (4th September 2015)

• Record Type: Journal Article
• Authors: Tuba, Robert; Xi, Zhenxing; Bazzi, Hassan S.; Gladysz, John A.
• Is Part Of: Chemistry. Volume 21:Issue 45(2015)
• Page Start: 15894
• Page End: 15906
• Publication Date: 2015-09-04
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201502403
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>With metal‐based catalysts, it is quite common that a ligand (L) must first dissociate from a catalyst precursor (L′_{<italic>n</italic>}ML) to activate the catalyst. The resulting coordinatively unsaturated active species (L′_{<italic>n</italic>}M) can either back react with the ligand in a <italic>k</italic>₋₁ step, or combine with the substrate in a <italic>k</italic>₂ step. When dissociation is not rate determining and <italic>k</italic>₋₁[L] is greater than or comparable to <italic>k</italic>₂[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.</p> </abstract>