New pallada- and platinacycle complexes of phosphorus ylide: Synthesis, structural characterization, antioxidant capacity and catalytic behavior towards Mizoroki-Heck reactions

Abstract

The reactions of α-keto stabilized phosphorus ylide Ph2P(CH2)2PPh2C(H)C(O)C6H4-m-Br (Y) with [MCl2(cod)] (M=Pd or Pt; cod=1,5-cyclooctadiene) in equimolar ratio using dichloromethane as a solvent are reported. These reactions led to the formation of new P, C-chelated pallada- and platinacycle complexes [MCl2(Ph2P(CH2)2PPh2C(H)C(O)C6H4-m-Br)] (M=Pd (C1) and Pt (C2)). Characterization of the obtained compounds was performed by elemental analysis and IR, 1H, 13C, and 31P NMR spectroscopic methods. Also, the unequivocal structures of these complexes were characterized crystallographically. Both structures consist of six-membered rings formed by coordination of the phosphorus ylide (Y) through the phosphine group and the ylidic carbon atom to the metal center. Furthermore, palladacycle C1 was employed as an efficient catalyst in the Mizoroki-Heck coupling reaction of several aryl chlorides and olefins. The coupled products of these reactions were obtained under aerobic conditions in high yields using aqueous DMF as a solvent. Additionally, the antioxidant capacity of the reported compounds with butylated hydroxytoluene (BHT) as standard was evaluated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging method. Apparently, all synthesized compounds possess strong antioxidant capacity (IC50; 0.584±0.009–0.751±0.003mg/ml).