Copper(I) complexes with N-(2-quinolinylmethylene)-1, 5-dimethyl- 2-phenyl-1-pyrazole-3-(2H)-one and phosphine as ligands: Effective catalyst for Sonogashira cross-coupling reaction

Abstract

A new series of copper(I) complexes of the type [Cu( L )(PPh 3 ) 2 ]X( 1a-c ) and [Cu( L )(dppe)]X ( 2a-c ) have been prepared by the reaction of Cu(MeCN) 4 ]X (Where X = ClO 4 - , BF 4 - and PF 6 - ) with N-(2-quinolinylmethylene)-1,5-dimethyl-2-phenyl-1-pyrazole-3-(2H)-one ( L ) in presence of triphenyl- phosphine (PPh 3 ) or 1,2-bis(diphenylphosphino)ethane (dppe) as an ancillary ligand. The UV–Visible spectra indicate that the ancillary phosphine ligands significantly perturb the MLCT state of copper(I) complexes. The thermally stable 1a-c and 2a-c complexes exhibit quasireversible redox behaviour corresponding to Cu(I)/Cu(II) couple. All complexes were tested as catalyst for Sonogashira cross-coupling of phenylacetylene with aryl iodide. The results showed that all complexes worked as an effective catalyst at low temperature yielded substituted aryl alkynes as a product. The nature of phosphine ligands and size of counter anions shows marked effect on their catalytic properties of all the complexes .