Spectral and crystallography studies of new palladacycle complexes with P,C- and C,C-donor ligands; Application of (OAL16) to optimizing the yield of Mizoroki-Heck reaction: palladacycle complexes with P,C- and C,C-donor ligands and application

The new symmetrical diphosphonium salt [Ph2P(CH2)(2)PPh2(CH2C(O)C6H4Br)(2)] Br-2 (S) was synthesized in the reaction of 1,2-bis (diphenylphosphino) ethane (dppe) and related ketone. Further treatment with NEt3 gave the symmetrical alpha-keto stabilized diphosphine ylide [Ph2P(CH2)(2)PPh2(CHC(O)C6H4Br)(2)] (Y-1). The unsymmetrical alpha-keto stabilized diphosphine ylide [Ph2P(CH2)(2)PPh2(CHC(O)C6H4Br)] (Y-2) was synthesized in the reaction of diphosphine in 1:1 ratio with 2.3 '-dibromoacetophenone, then treatment with NEt3. The reaction of dibromo (1,5-cyclooctadiene)palladium (II), [PdBr2(COD)] with this ligand (Y-1) in equimolar ratio gave the new C,C-chelated [PdBr2(Ph2P(CH2)(2)PPh2(C(H)C(O)C6H4Br)(2))] (1) and with unsymmetrical phosphorus ylide [Ph2P(CH2)(2)PPh2C(H)C(O)C6H4Br] (Y-2) gave the new P, C-chelated palladacycle complex [PdBr2(Ph2P(CH2)(2)PPh2C(H)C(O)Br)] (2). These compounds were characterized successfully by FT-IR, NMR (H-1, C-13 and P-31) spectroscopic methods and the crystal structure of Y-1 and 2 were elucidated by single crystal X-ray diffraction. The results indicated that the complex 1 was C, C-chelated whereas complex 2 was P, C-chelated. These air/moisture stable complexes were employed as efficient catalysts for the Mizoroki-Heck cross-coupling reaction of several aryl chlorides, and the Taguchi method was used to optimize the yield of Mizoroki-Heck coupling. The optimum condition was found to be as followed: base; K2CO3, solvent; DMF and loading of catalyst; 0.005 mmol.