14588-08-0Relevant articles and documents
Lightly fluorous [Pd(OAc)2{P(C6H4-p-SiMe2CH2CH2C6F13)3}2] in the methoxycarbonylation of styrene: Formation, performance and stability of the catalyst system
de Pater, Jeroen J.M.,Deelman, Berth-Jan,Elsevier, Cornelis J.,van Koten, Gerard
, p. 334 - 340 (2006)
The fluorous palladium(II) complex, [Pd(OAc)2{P(C6H4-p-SiMe2CH2CH2C6F13)3}2], has been prepared and characterized. Its application in the catalytic methoxycarbonylation of styrene in an MeOH/CF3C6H5 mixture (1/1 v/v) has been explored and its activity was compared to that of [Pd(OAc)2(PPh3)2]. The fluorous complex showed a lower activity but a significantly higher selectivity towards the branched product. Investigation of both the conversion-versus-time and i:n ratio-versus-time profiles showed an unusual behaviour in the case of the fluorous complex, which has been ascribed to the formation of a dinuclear species for the fluorous complex.
The ubiquitous cross-coupling catalyst system 'Pd(OAc)2'/2PPh3 forms a unique dinuclear PdI complex: An important entry point into catalytically competent cyclic Pd3 clusters
Scott, Neil W. J.,Ford, Mark J.,Schotes, Christoph,Parker, Rachel R.,Whitwood, Adrian C.,Fairlamb, Ian J. S.
, p. 7898 - 7906 (2019/09/06)
Palladium(ii) acetate 'Pd(OAc)2'/nPPh3 is a ubiquitous precatalyst system for cross-coupling reactions. It is widely accepted that reduction of in situ generated trans-[Pd(OAc)2(PPh3)2] affords [Pd0(PPh3)n] and/or [Pd0(PPh3)2(OAc)]- species which undergo oxidative addition reactions with organohalides-the first committed step in cross-coupling catalytic cycles. In this paper we report for the first time that reaction of Pd3(OAc)6 with 6 equivalents of PPh3 (i.e. a Pd/PPh3 ratio of 1?:?2) affords a novel dinuclear PdI complex [Pd2(μ-PPh2)(μ2-OAc)(PPh3)2] as the major product, the elusive species resisting characterization until now. While unstable, the dinuclear PdI complex reacts with CH2Cl2, p-fluoroiodobenzene or 2-bromopyridine to afford Pd3 cluster complexes containing bridging halide ligands, i.e. [Pd3(X)(PPh2)2(PPh3)3]X, carrying an overall 4/3 oxidation state (at Pd). Use of 2-bromopyridine was critical in understanding that a putative 14-electron mononuclear 'PdII(R)(X)(PPh3)' is released on forming [Pd3(X)(PPh2)2(PPh3)3]X clusters from [Pd2(μ-PPh2)(μ2-OAc)(PPh3)2]. Altering the Pd/PPh3 ratio to 1?:?4 forms Pd0(PPh3)3 quantitatively. In an exemplar Suzuki-Miyaura cross-coupling reaction, the importance of the 'Pd(OAc)2'/nPPh3 ratio is demonstrated; catalytic efficacy is significantly enhanced when n = 2. Employing 'Pd(OAc)2'/PPh3 in a 1?:?2 ratio leads to the generation of [Pd2(μ-PPh2)(μ2-OAc)(PPh3)2] which upon reaction with organohalides (i.e. substrate) forms a reactive Pd3 cluster species. These higher nuclearity species are the cross-coupling catalyst species, when employing a 'Pd(OAc)2'/PPh3 of 1?:?2, for which there are profound implications for understanding downstream product selectivities and chemo-, regio- and stereoselectivities, particularly when employing PPh3 as the ligand.
PROCESS FOR THE PREPARATION OF UNSYMMETRICALLY SUBSTITUTED BIPHENYL COMPOUNDS
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Page/Page column 10, (2008/12/07)
A process for the preparation of unsymmetrical biaryl compounds of Formula (I) wherein, R is alkyl, R' is cyano, protected or unprotected tetrazole, or Formula (a) wherein, R" is alkyl, aryl, aralkyl or alkoxy, said process comprising, reacting Grignard reagent of Formula (II) wherein, R is alkyl; X is halogen with an aryl halide of Formula (III) wherein, X is halogen; R' is a cyano, protected or unprotected tetrazole, or Formula (a) wherein, R" is alkyl, aryl, aralkyl or alkoxy in a suitable solvent in the presence of a palladium catalyst and a ligand and Lewis acid as a co catalyst.