The Synthesis Of Chiral Pincer Complexes And Their Applications In Asymmetric Reaction

This thesis is focused on the synthesis and characterization of unsynmmetrical chiral N-P bond-based PCN Pd(Ⅱ)/Ni(Ⅱ) complexes, unsynmmetrical chiral NCN' pincer Pt(Ⅱ) complexes, NCN pincer Pt(Ⅱ)/Pd(Ⅱ) complexes containing several chiral centers, Their applications in asymmetric catalysis are also presented and compared.1. Synthesis and characterizaiton of unsymmetrical chiral PCN pincer complexes.The required ligands 3a-c were prepared via the three-step sequencing reactions from commercially available m-Nitrobenzoic acid. The N-P bond-based PCN Pd(Ⅱ)/Ni(Ⅱ) complexes 4a-c and 5a could be accessed by the "one-pot phosphorylation/palladation" approach. (Scheme 1). All the new compounds were characterized by NMR, HRMS and IR spectra. The molecular structures of 4a,4c and 5a were further confirmed by elemental analysis and X-ray single-crystal diffraction.2. Synthesis and characterizaiton of unsymmetrical chiral NCN'pincer complexes and symmetrical NCN pincer complexes (a) Unsymmetrical chiral NCN'Pt(II) complexes.The new pincer ligands 6a-c bearing imidazolinyl and oxazaolinyl groups were synthesized from readily available isophthalic acid and chiral amino alcohols in three steps. Ligands 6a-c reacted with K2PtCl4 in hydrous HOAc, directly led to the formation of unsymmetrical chiral NCN'pincer complexes 7a-c (Scheme 2). Complex 8c was prepared from the chloro-platinum 7c by treatment with an excess of KI in acetone at room temperature. By means of IR, MS,1H NMR,13C NMR, and elemental analysis, the molecular structures of compounds 6-8 were characterized. X-ray single-crystal diffraction further confirmed the molecular structure of 7b.(b) Symmetrical NCN Pt(II)/Pd(II) complexes containing several chiral centers.The chiral ligands 1,3-bis(2'-imidazolinyl)benzene 10 was synthesized from isophthalic acid and chiral amino alcohols in two steps (Scheme 3). Reactions of 10 with K2PtCl4 or Pd(OAc)2 directly led to the formation of corresponding chiral bis(imidazoline) NCN Pt(II)/Pd(II) complexes by the direct Caryi-H activation method. The compounds 11 and 13 were obtained by the halogen exchange reaction. Halide abstraction on 11 proceeded in CH2Cl2/H2O with AgOTf to give platinum complex 12 (Scheme 3). All of the new pincer complexes were characterized by IR, MS,1H NMR, 13C NMR and elemental analysis. The structures of the compounds 11-13 were further confirmed by single-crystal X-ray analysis.3 Applications of chiral pincer complexes in the asymmetric reaction.The catalytic activities of pincer complexes in conjugate phosphination of electron-deficient acceptors was investigated (Scheme 4), the catalyst 4c displayed the efficient reactivity, under the condition of 0℃, toluene as solvent, KOAc as base, and 5 mol% catalyst loading, the adducts could been obtained with up to 99% yield and 94% ee.