Amination and Suzuki coupling reactions catalyzed by palladium complexes coordinated by cobalt-containing monodentate phosphine ligands with bis-trifluoromethyl substituents on bridged arylethynyl: Observation of some unusual metal-containing compounds

Abstract

Two cobalt-containing bulky monodentate phosphines {[(μ-PPh 2CH 2PPh 2)Co 2(CO) 4][(μ,η-( t Bu) 2PC CAr]} ( 4cm: Ar = 3-CF 3C 6H 4; 4cmm: Ar = 3,5-(CF 3) 2C 6H 3) were prepared from the reaction of Co 2(CO) 6(μ-PPh 2CH 2PPh 2) ( 3) with each corresponding alkynes ( t Bu) 2PC CAr. Both compounds were converted to their oxidized forms {[(μ-PPh 2CH 2PPh 2)Co 2(CO) 4][(μ,η-( t Bu) 2P( O)C CAr]} ( 4cmO: Ar = 3-CF 3C 6H 3; 4cmmO: Ar = 3,5-(CF 3) 2C 6H 3) in the presence of oxide. Further reactions of 4cm and 4cmm with Pd(OAc) 2 gave palladium complexes {[(μ-PPh 2CH 2PPh 2)Co 2(CO) 4][(μ,η-( t Bu) 2PC C(Ar)-κC 1)]Pd(μ-OAc)} 5cm (Ar = 3-CF 3C 6H 3) and 5cmm (Ar = 3,5-(CF 3) 2C 6H 2), respectively. By contrast, reactions of 4cm and 4cmm with Pd(COD)Cl 2 gave products, [{μ-P,P-PPh 2CH 2PPh 2}Co 2(CO) 3(μ-CO){μ,η-( t Bu) 2PC CAr}]-PdCl 2] 8cm and 8cmm, respectively, with unique bonding modes. Several crystallines of [( 4cm) 2Pd 3(μ-Cl)(μ-CO) 2)(μ-Cl)] 2 ( 9) were obtained along with crystallines of 8cm during the crystallization process. The crystal structures of all three compounds, 4cmmO, 8cmm and 9 were determined by single-crystal X-ray diffraction methods. Fair to excellent efficiencies were observed for employing 4cmm/palladium salt as catalytic precursor in amination as well as in Suzuki coupling reactions.