852813-33-3Relevant academic research and scientific papers
Bulky triarylarsines are effective ligands for palladium catalysed Heck olefination
Baber, R. Angharad,Collard, Simon,Hooper, Mark,Orpen, A. Guy,Pringle, Paul G.,Wilkinson, Matthew J.,Wingad, Richard L.
, p. 1491 - 1498 (2005)
The four arsines, As{C6H3(o-CH3)(p-Z)} 3 {Z = H (2a) or OMe (2b)} and As{C6H3(o- CHMe2)(p-Z)}3 {Z = H (2c) or OMe (2d)} react with [PdCl2(NCPh)2] or [PtCl2(NCBu1) 2] to give trans-[MCl2L2] or trans-[M 2Cl2(μ-Cl)2L2]. The crystal structures of trans-[PdCl2(2a)2] and [PtCl 2(2d)2] have been determined, the latter as its dichloromethane solvate. The structures show that in these complexes, the ligands adopt gga type conformations as do all analogous tri-o-tolyl- and tri-o-isopropylphenylphosphines in square-planar and octahedral complexes. The variable-temperature NMR behaviour of the complexes shows that they are fluxional due to restricted As-C bond rotation. The rate of the fluxionality is more rapid than in the analogous phosphine complexes and this is associated with longer As-C and As-M bonds allowing more free movement. The catalytic activity of the palladium complexes of the arsines and their phosphine analogues for the reaction of 4-bromoacetophenone and n-butyl acrylate has been screened. The results show that the arsines are generally superior to the phosphines as ligands for this catalysis. Tri(o-isopropylphenyl)phosphine and tri(o-isopropylphenyl)arsine are superior to tri-o-tolylphosphine as ligands for this Heck reaction and a p-methoxy substituent improves the arsine catalyst but not the phosphine catalyst. The phosphine catalysts are superior to the arsine catalysts for the reaction of 4-chloroacetophenone and n-butyl acrylate. These observations are discussed in the context of ligand stereoelectronic effects, as measured by the Tolman electronic parameter, vCO of the [NiL(CO)3] {L = AsAr3 or PAr3}. The Royal Society of Chemistry 2005.
