Palladium(II) complexation of ambidentate cis-s-cis-enaminones: synthesis of some bis(4-anilinopent-3-en-2-onato)- and bis(3-amino-1-phenylbut-2-en-1-onato)-complexes of palladium(II) and X-ray crystal structure of bis[4-(2-bromoanilino)pent-3-en-2-onato]palladium(II)

Abstract

Condensation of acetylacetone with anilines gives N-aryl derivatives of 4-aminopent-3-en-2-one. Similar treatment of benzoylacetone with various primary amines yields N-substituted 3-amino-1-phenylbut-2-en-1-ones. Both series of products with the cis-s-cis-enaminone structure behave as bidentate ligands for Pd^II to yield stable yellow complexes, the structures of which have been determined as bis(4-anilinopent-3-en-2-onato)- and bis(3-amino-1-phenylbut-2-en-1-onato)-complexes of palladium(II), respectively. To establish the structure of the complex in the solid state, X-ray crystal structure analyses have been carried out on bis[4-(2-bromoanilino)pent-3-en-2-onato]palladium(II). The crystals of the complex solvated by benzene are triclinic and belong to space group P, with cell dimensions a= 8.034(5), b= 11.613(5), c= 7.637(10)Å, α= 98.67(5), β= 88.44(5), γ= 100.22(10)°, and Z= 1. The crystal structure has been solved using 2 951 reflections and refined to a final R value of 0.092. The Pd atom takes a square-planar co-ordination and the ligand molecules with the cis-s-cis-enaminone system form six-membered chelate rings with the metal.