1256169-43-3Relevant academic research and scientific papers
Negishi cross-coupling reaction catalyzed by an aliphatic, phosphine based pincer complex of palladium. biaryl formation via cationic pincer-type Pd IV intermediates
Gerber, Roman,Blacque, Olivier,Frech, Christian M.
experimental part, p. 8996 - 9003 (2011/10/31)
The aliphatic, phosphine-based pincer complex [(C10H 13-1,3-(CH2P(Cy2)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 [(C10H13-1,3-(CH2P(C6H 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 [(C10H 13-1,3-(CH2P(Cy2)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 [(C10H13-1,3-(CH 2P(Cy2)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. The Royal Society of Chemistry 2011.
