Synthesis and characterization of new bis(diphenylphosphino)aniline ligands and their complexes: X-ray crystal structure of palladium(II) and platinum(II) complexes, and application of palladium(II) complexes as pre-catalysts in Heck and Suzuki cross-coupling reactions

Abstract

Two new bis(diphenylphosphino)isopropylphenylamines, (PPh 2) 2N-C 6H 4-CH(CH 3) 2, having the isopropyl substituent at the carbon atom 2 ( 1) or 4 ( 2), were prepared by the aminolysis of chlorodiphenylphosphine with isopropyl substituted aniline at the ortho- or para-position, respectively, under anaerobic conditions. Oxidation of 1 and 2 with either aqueous hydrogen peroxide, elemental sulfur or grey selenium in thf gave the corresponding oxides, sulfides and selenides (Ph 2P E) 2N-C 6H 4-CH(CH 3) 2, where E = O, S or Se, respectively. The palladium and platinum complexes [M{(Ph 2P) 2N-C 6H 4-CH(CH 3) 2}Cl 2] (M = Pd, Pt) and the copper complex [Cu{(Ph 2P) 2N-C 6H 4-CH(CH 3) 2} 2]PF 6 were isolated from the reaction of the bis(phosphino)anilines with MCl 2(cod) or [Cu(CH 3CN) 4]PF 6, respectively. The new compounds were characterized by NMR, IR spectroscopy and elemental analysis. Furthermore, the solid-state structures of two representative complexes were determined using single crystal X-ray diffraction analysis. The compounds of palladium ( 1d) and platinum ( 1e), both mononuclear complexes, crystallize in the monoclinic P2 1/ c space group. In both compounds the metal ion has a distorted square–planar coordination geometry. The structural properties of complexes 1d and 1e in the solid state are very similar. The palladium complexes were also tested for their catalytic activities in C–C coupling reactions.