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      SYNTHESIS, CHARACTERISATION AND CATALYTIC ACTIVITY OF GOLD, RHODIUM AND PALLADIUM COMPLEXES FEATURING FLUORINATED N-HETEROCYCLIC CARBENE LIGANDS

      Jamil, Mohamad Shazwan shah

      [Thesis]. Manchester, UK: The University of Manchester; 2018.

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      Abstract

      This thesis describes the development of gold, rhodium and palladium complexes incorporating a series of fluorinated N-heterocyclic carbene (NHC) ligands (NHC = 1,3-bis(fluorophenyl)imidazol-2-ylidene, fluorophenyl = 4-fluorophenyl (NHC-1), 2,4-difluorophenyl (NHC-2), 2,6-difluorophenyl (NHC-3), 2,4,5-trifluorophenyl (NHC-4) and 2,4,6-trifluorophenyl (NHC-5) and examines their steric and electronic properties and catalytic activities. The electronic properties have been evaluated by investigating the 77Se NMR chemical shifts of the corresponding selenium adducts, Se(NHC-1), Se(NHC-2), Se(NHC-3), Se(NHC-4) and Se(NHC-5). Comparative studies revealed that the fluorinated NHC ligands have stronger ĂŹ€-accepting abilities than the non-fluorinated NHC counterparts, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) and 1,3-bis(phenyl)imidazol-2-ylidene (IPh). The novel gold(I) complexes featuring fluorinated NHC ligands, [AuCl(NHC-1)] (Au-1), [AuCl(NHC-2)] (Au-2), [AuCl(NHC-3)] (Au-3), [AuCl(NHC-4)] (Au-4) and [AuCl(NHC-5)] (Au-5) have been synthesised and employed in the A3 coupling reaction of benzaldehyde, dibenzylamines and phenylacetylene. The catalytic activities of these complexes increased in the order of increasing steric bulk and ĂŹ€-accepting abilities of the NHC ligands. The preparation of the rhodium(I) complexes bearing fluorinated NHC ligands, [Rh(cod)Cl(NHC-1)] (Rh-21), [Rh(cod)Cl(NHC-2)] (Rh-22), [Rh(cod)Cl(NHC-3)] (Rh-23), [Rh(cod)Cl(NHC-4)] (Rh-24) and [Rh(cod)Cl(NHC-5)] (Rh-25) is reported. The catalytic activities of Rh-21, Rh-22, Rh-23, Rh-24 and Rh-25 in the transfer hydrogenation of acetophenone to 1-phenylethanol were exceptionally higher than non-fluorinated derivatives, [Rh(cod)Cl(IPh)] (Rh-26) and [Rh(cod)Cl(IMes)] (Rh-27). The new palladium(II) complexes containing fluorinated NHC ligands, [Pd(NHC-1)(3-Cl-pyridyl)Cl2] (Pd-21), [Pd(NHC-2)(3-Cl-pyridyl)Cl2] (Pd-22), [Pd(NHC-3)(3-Cl-pyridyl)Cl2] (Pd-23), [Pd(NHC-4)(3-Cl-pyridyl)Cl2] (Pd-24) and [Pd(NHC-5)(3-Cl-pyridyl)] (Pd-25) have been prepared and tested in the Suzuki-Miyaura coupling of phenylboronic acid and 4-iodotoluene. All these complexes have better catalytic performance than those of the non-fluorinated counterparts, [Pd(IMes)(3-Cl-pyridyl)Cl2] (Pd-14) and [Pd(IPh)(3-Cl-pyridyl)Cl2] (Pd-26). The findings from this work suggest that the presence of fluorine in NHC ligands affects the steric and electronic properties and enhances the metal complexes catalytic activities in various organic reactions. The link between the steric and electronic properties of the fluorinated NHCs and the outcome of the reactions in each catalytic system was investigated and reported in this thesis.

      Additional content not available electronically

      CD-Rom containing the Crystallographic Information File (CIF)

      Bibliographic metadata

      Type of resource:
      Content type:
      Administered thesis
      Form of thesis:
      Traditional
      Type of submission:
      Doctoral level ETD - final
      Thesis title:
      SYNTHESIS, CHARACTERISATION AND CATALYTIC ACTIVITY OF GOLD, RHODIUM AND PALLADIUM COMPLEXES FEATURING FLUORINATED N-HETEROCYCLIC CARBENE LIGANDS
      Degree type:
      Doctor of Philosophy
      Degree programme:
      PhD Chemistry
      Publication date:
      2018-12-07T10:01:48
      Institution:
      The University of Manchester
      Location:
      Manchester, UK
      Total pages:
      262
      Abstract:
      This thesis describes the development of gold, rhodium and palladium complexes incorporating a series of fluorinated N-heterocyclic carbene (NHC) ligands (NHC = 1,3-bis(fluorophenyl)imidazol-2-ylidene, fluorophenyl = 4-fluorophenyl (NHC-1), 2,4-difluorophenyl (NHC-2), 2,6-difluorophenyl (NHC-3), 2,4,5-trifluorophenyl (NHC-4) and 2,4,6-trifluorophenyl (NHC-5) and examines their steric and electronic properties and catalytic activities. The electronic properties have been evaluated by investigating the 77Se NMR chemical shifts of the corresponding selenium adducts, Se(NHC-1), Se(NHC-2), Se(NHC-3), Se(NHC-4) and Se(NHC-5). Comparative studies revealed that the fluorinated NHC ligands have stronger ĂŹ€-accepting abilities than the non-fluorinated NHC counterparts, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) and 1,3-bis(phenyl)imidazol-2-ylidene (IPh). The novel gold(I) complexes featuring fluorinated NHC ligands, [AuCl(NHC-1)] (Au-1), [AuCl(NHC-2)] (Au-2), [AuCl(NHC-3)] (Au-3), [AuCl(NHC-4)] (Au-4) and [AuCl(NHC-5)] (Au-5) have been synthesised and employed in the A3 coupling reaction of benzaldehyde, dibenzylamines and phenylacetylene. The catalytic activities of these complexes increased in the order of increasing steric bulk and ĂŹ€-accepting abilities of the NHC ligands. The preparation of the rhodium(I) complexes bearing fluorinated NHC ligands, [Rh(cod)Cl(NHC-1)] (Rh-21), [Rh(cod)Cl(NHC-2)] (Rh-22), [Rh(cod)Cl(NHC-3)] (Rh-23), [Rh(cod)Cl(NHC-4)] (Rh-24) and [Rh(cod)Cl(NHC-5)] (Rh-25) is reported. The catalytic activities of Rh-21, Rh-22, Rh-23, Rh-24 and Rh-25 in the transfer hydrogenation of acetophenone to 1-phenylethanol were exceptionally higher than non-fluorinated derivatives, [Rh(cod)Cl(IPh)] (Rh-26) and [Rh(cod)Cl(IMes)] (Rh-27). The new palladium(II) complexes containing fluorinated NHC ligands, [Pd(NHC-1)(3-Cl-pyridyl)Cl2] (Pd-21), [Pd(NHC-2)(3-Cl-pyridyl)Cl2] (Pd-22), [Pd(NHC-3)(3-Cl-pyridyl)Cl2] (Pd-23), [Pd(NHC-4)(3-Cl-pyridyl)Cl2] (Pd-24) and [Pd(NHC-5)(3-Cl-pyridyl)] (Pd-25) have been prepared and tested in the Suzuki-Miyaura coupling of phenylboronic acid and 4-iodotoluene. All these complexes have better catalytic performance than those of the non-fluorinated counterparts, [Pd(IMes)(3-Cl-pyridyl)Cl2] (Pd-14) and [Pd(IPh)(3-Cl-pyridyl)Cl2] (Pd-26). The findings from this work suggest that the presence of fluorine in NHC ligands affects the steric and electronic properties and enhances the metal complexes catalytic activities in various organic reactions. The link between the steric and electronic properties of the fluorinated NHCs and the outcome of the reactions in each catalytic system was investigated and reported in this thesis.
      Additional digital content not deposited electronically:
      CD-Rom containing the Crystallographic Information File (CIF)
      Keyword(s):
      Thesis main supervisor(s):
      Thesis co-supervisor(s):
      Funder(s):
      Degree grantor:
      Language:
      en

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        Record metadata

        Manchester eScholar ID:
        uk-ac-man-scw:317492
        Created by:
        Jamil, Mohamad Shazwan shah
        Created:
        7th December, 2018, 10:01:48
        Last modified by:
        Jamil, Mohamad Shazwan shah
        Last modified:
        13th January, 2020, 10:59:42

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