Loading…
Bulky triarylarsines are effective ligands for palladium catalysed Heck olefination
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(NCBu(t))2] to give trans-[MCl2L2] or trans-[M2Cl2(mu-Cl)2L2]. The crystal structures of trans-[PdCl2(2a)2] and [PtCl2(2d)2] have been determined, the la...
Saved in:
Published in: | Dalton transactions : an international journal of inorganic chemistry 2005-04 (8), p.1491-1498 |
---|---|
Main Authors: | , , , , , , |
Format: | Article |
Language: | English |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
Summary: | 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(NCBu(t))2] to give trans-[MCl2L2] or trans-[M2Cl2(mu-Cl)2L2]. The crystal structures of trans-[PdCl2(2a)2] and [PtCl2(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, nuCO of the [NiL(CO)3]{L=AsAr3 or PAr3}. |
---|---|
ISSN: | 1477-9226 1477-9234 |
DOI: | 10.1039/b417910b |