Title: Negishi cross-coupling reaction catalyzed by an aliphatic, phosphine based pincer complex of palladium biaryl formation via cationic pincer-type PdIV intermediates
Authors : Gerber, Roman
Blacque, Olivier
Frech Nabold, Christian M.
Published in : Dalton transactions
Volume(Issue) : 40
Issue : 35
Pages : 8996
Pages to: 9003
Publisher / Ed. Institution : Royal Society of Chemistry
Issue Date: 2011
License (according to publishing contract) : Licence according to publishing contract
Type of review: Peer review (Publication)
Language : English
Subject (DDC) : 540: Chemistry
Abstract: The aliphatic, phosphine-based pincer complex [(C(10)H(13)-1,3-(CH(2)P(Cy(2))(2))Pd(Cl)] (1) is a highly active Negishi catalyst, enable to quantitatively couple various electronically activated, non-activated, deactivated, sterically hindered and functionalized aryl bromides with various diarylzinc reagents within short reaction times and low catalyst loadings. Experimental observations strongly indicate that a molecular mechanism is operative with initial chloride dissociation of 1 and formation of the cationic T-shaped 14e(-) complex [(C(10)H(13)-1,3-(CH(2)P(C(6)H(11))(2))(2))Pd](+) (B), which undergoes oxidative addition of an aryl bromide (Ar'Br) to yield the cationic, penta-coordinated aryl bromide pincer complexes of type [(C(10)H(13)-1,3-(CH(2)P(Cy(2))(2))Pd(Br)(aryl')](+) (C) with the metal center in the oxidation state of +IV and the aryl unit in cis position relative to the aliphatic pincer core. Subsequent transmetalation with Zn(aryl)(2) result in the cationic diaryl pincer complexes of type [(C(10)H(13)-1,3-(CH(2)P(Cy(2))(2))Pd(aryl)(aryl')](+) (D), which reductively eliminate the coupling products, thereby regenerating the catalyst. The neutral square planar aryl pincer complex--a possible key intermediate in the catalytic cycle--was found to be reversibly formed in the reaction mixture but is not involved in the catalytic mechanism. Similarly, palladium nanoparticles as the catalytically active form of 1 could have been excluded.
Departement: Life Sciences and Facility Management
Publication type: Article in scientific Journal
DOI : 10.1039/c1dt10398a
ISSN: 1477-9226
1477-9234
URI: https://digitalcollection.zhaw.ch/handle/11475/10464
Appears in Collections:Publikationen Life Sciences und Facility Management

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