Synthesis Of Nickel And Palladium Complexes And Their Catalysis In The Cross-Coupling Reactions

This thesis presents synthesis and characterization of nickel and palladium complexes bearing P,N,O-and P,N,S-pincer ligands and catalysis of the complexes towards Kumada reaction and Negishi reaction. The catalytic cross-coupling reactions of organometallic reagents with aryl nitriles or organomanganese reagents with aryl fluorides using the combination of transition metal salts and appropriate ligands are also discussed.Chapter1describes synthesis and characterization of anionic P,N,O-and P,N,S-ligands and their nickel and palladium complexes. The nickel complexes were synthesized through reaction of the anionic P,N,O-and P,N,S-ligands with NiCl2(DME), including:[Ni(Cl){2-(Ph2P(S))C6H4NCH(Ph)PPh2}](1.1),[Ni(Cl){2-(Ph2P(O))C6H4NCH(Ph)PPh2}](1.2),[Ni(Cl){2-(Ph2P)C6H4NCH(Ph)-P(S)Ph2}](1.3) and [Ni(Cl){2-(Ph2P)C6H4NCH(Ph)P(O)Ph(R)}](1.4a, R=Ph;1.4b, R=Et). A palladium complex [Pd(Cl){2-(Ph2P)C6H4NCH(Ph)P(O)Ph2}](1.5) was similarly synthesized by reaction of [Li{2-(Ph2P)C6H4NCH(Ph)P(O)Ph2}] with [PdCl2(PhCN)2]. Complexes1.1and1.2were characterized by elemental analyses and mass spectra. Complexes1.3,1.4a,1.4b and1.5were characterized by NMR spectroscopy and elemental analyses. The structures of complexes1.3and1.4a were further characterized by single-crystal X-ray diffraction techniques.Chapter2is about catalysis of nickel complexes1.la-1.4b towards the Kumada cross-coupling reaction. Among the complexes tested, the P,N,S-pincer nickel complexes1.1and1.3exhibited relatively low catalytic activity. By contrast, the P,N,O-pincer nickel complexes1.2,1.4a and1.4b showed excellent catalytic activity for the coupling reactions of unactivated and deactivated aryl, heteroary, and vinyl chlorides with aryl Grignard reagents. In the presence of LiCl and ZnCl2additives, the reactions tolerate functional groups such as ester, ketone, carboxamide, and trifluoromethyl groups. This work significantly expands the substrate scope of Kumada cross-coupling reactions.Chapter3deals with catalysis of nickel complexes1.la-1.4b towards the Negishi cross-coupling reaction. P,N,O-pincer nickel complexes1.2,1.4a and1.4b show higher catalytic activity compared with the P,N,S-pincer nickel complexes. The P,N,O-pincer nickel complexes are able to efficiently catalyze cross-coupling of unactivated and deactivated aryl chlorides with arylzinc reagents at room temperature with low catalyst loadings. The reaction showed good functional group tolerance and wide scope of substrates. The reaction of polychlorinated benzenes with arylzinc chlorides also proceeds smoothly under the same condition. In addition, reaction between aryl chlorides and electron-deficient zinc reagent in the presence of palladium complexes1.5led to excellent product yields at room temperature.Chapter4introduces a series of transition-metal-catalyzed cross-couplings of aryl nitriles and arylmetallic reagents, including Ni(acac)2/Ph2POH-catalyzed cross-coupling of aryl-or heteroaryl nitriles and aryl Grignard reagents, Pd(OAc)2/(p-MeOC6H4)2POH-catalyzed cross-coupling of aryl nitriles and arylzinc reagents, and Ni(PMe3)2Cl2-catalyzed cross-coupling of aryl-or heteroaryl nitriles and aryl-or heteroarylmanganese reagent. The Ni(PMe3)2Cl2-catalyzed cross-coupling display a broad substrate scope and tolerates functional groups such as ester, amide, trifluoromethyl, fluoride, methyloxy, dimethylamino, and heteroaryl groups.Chapter5presents an efficient nickel-catalyzed cross-coupling reaction of aryl-or heteroaryl fluorides with arylmanganese reagents. Ni(PCy3)2Cl2or Ni(COD)2/2IPr·HCl were proved to be the efficient catalysts for the reactions of electron-deficient or electron-rich aryl-or heteroaryl fluorides; functional groups such as ester, carboxamide, and trifluoromethyl groups can be tolerated.