Synthesis And Catalytic Properties Of Ncn Pincer Rhodium(?) And Cnn Pincer Palladium(?) And Ruthenium(?) Complexes

In this dissertation, the synthesis, characterization and catalytic application ofchiral NCN pincer rhodium(III) complexes with bis(imidazolinyl)phenyl ligands andunsymmetrical CNN pincer palladium(II) and ruthenium(II) complexes were studied.The main results are as follows:1. Synthesis, characterizaiton and catalytic properties of chiral NCN pincerrhodium(III) complexes with bis(imidazolinyl)phenyl ligands(1) Synthesis and characterizaiton of chiral NCN pincer rhodium(III) complexeswith bis(imidazolinyl)phenyl ligandsChiral bis(imidazolinyl)phenyl ligands1a-f were synthesized in a three-stepsequence from commercially available1,3-benzene dicarbonyl dichloride or5-nitro-1,3-benzene dicarbonyl dichloride and chiral amino alcohols. Then thereaction of ligands1and triply hydrated rhodium trichloride afforded thecorresponding chiral NCN pincer rhodium(III) chloride complexes[(Phebim)RhCl2(H2O)]2via aryl C-H bond activation of the related ligands. Therhodium chloride complexes2were readily converted to the corresponding rhodiumacetate complexes [(Phebim)Rh(OAc)2(H2O)]3by reaction with an excess of silveracetate (Scheme1). All of the new compounds were fully characterized by elementalanalysis (HR-MS for the new ligands1d and1e),1H NMR,13C NMR, and IR spectra.In addition, the formation of the expected NCN pincer Rh(III) complexes isunambiguously confirmed by the single crystal X-ray diffraction analysis ofcomplexes2c' and2d', in which dichloromethane or acetone molecule, the solventused in recrystallization took the place of the H2O molecule in complexes2c and2d. (2) Application of NCN pincer rhodium(III) complexes [(Phebim)RhCl2(H2O)] in the asymmetric catalytic reactionThe catalytic properties of pincer rhodium(III) complexes [(Phebim)RhCl2(H2O)]2in the asymmetric allylation of a variety of electronically and structurally diverse aldehydes with allyltributyltin were studied. The corresponding optically active homoallylic alcohols4were successfully prepared with enantioselectivities of up to97%ee and high yields (Scheme2). With the aid of silver trifluoromethanesulfonate, the pincer rhodium(III) catalysts could also catalyze the carbonyl-ene reaction of trifluoropyruvate with various2-arylpropenes to provide the corresponding chiral a-hydroxy-a-trifluoromethyl esters5in89%yield with enantioselectivities of up to95%ee. (3) Application of NCN pincer rhodium(III) complexes [(Phebim)Rh(OAc)2(H2O)] in the asymmetric catalytic reactionThe catalytic properties of pincer rhodium(III) complexes [(Phebim)Rh(OAc)2(H2O)]3in the asymmetric alkynylation of a variety of electronically and structurally diverse terminal alkynes with trifluoropyruvate were investigated. The optically active trifluoromethyl-substituted tertiary propargylic alcohols6were successfully prepared with enantioselectivities of up to>99%ee and high yields (Scheme3). The pincer rhodium(III) catalysts could also apply in the asymmetric alkynylation of various terminal alkynes with a-ketiminoesters to give the corresponding chiral a-trifluoromethyl-substituted a-amino acid derivatives7with enantioselectivities of up to83%ee and high yields.2. Synthesis, characterizaiton and catalytic properties of unsymmetrical CNN pincer palladium(II) and ruthenium(II) complexes(1) Synthesis and characterizaiton of unsymmetrical CNN pincer palladium(II) and ruthenium(II) complexesThe Suzuki coupling reaction of commercially available 6-bromo-2-picolinaldehyde and arylboronic acid in the presence of Pd(PPh3)4readily gave6-aryl-2-picolinaldehyde8. Then the expected ligands9-11were prepared by the reaction of the aldehyde group in compounds8with aliphatic or aromatic amines, hydroxylamine hydrochloride and chiral amino alcohols, respectively. With the ligands in hand, the metalization was carried out by refluxing the ligands9-11with PdCl2or [RuCl2(PPh3)(dppb)] to afford the corresponding unsymmetrical CNN pincer metal complexes12-16via aryl C-H bond activation (Scheme4). All the new compounds were fully characterized by elemental analysis (MS for ligands),1H NMR,13C NMR, and IR spectra. In addition, the molecular structure of the complexes12c,13-14,15c-f and16were further confirmed by the single crystal X-ray diffraction analysis.(2) Catalytic properties of achiral CNN pincer metal complexes with N-substituted-2-aminomethyl-6-phenylpyridinesThe obtained achiral CNN pincer palladium(II) complexes12were effective catalysts for the allylation of aldehydes as well as for three-component allylation of aldehydes, arylamines and allyltributyltin (Scheme5). On the other hand, the two novel CNN pincer ruthenium(?) complexes13and14displayed excellent catalytic activity in the transfer hydrogenation of ketones, the final TOF values were up to220800h-1(3) Application of chiral CNN pincer palladium(?) complexes with2-aryl-6-(oxazolinyl)pyridines in the asymmetric catalytic reactionThe obtained chiral CNN pincer palladium(?) complexes15were successfully used in the asymmetric allylation of isatins with allyltributyltin, giving the corresponding3-allyl-3-hydroxyoxindoles20in high yields with enantioselectivities of up to86%ee (Scheme6). These pincer palladium(?) catalysts could also catalyze the asymmetric Suzuki-Miyaura coupling reaction to provide the axially chiral biaryl products21in good yields with good stereoselectivities (up to68%ee).