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Title: Synthesis, characterisation and catalytic activity of gold, rhodium and palladium complexes featuring fluorinated n-heterocyclic carbene ligands
Author: Jamil, Mohamad Shazwan Shah Bin
ISNI:       0000 0004 8504 4626
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2019
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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 π-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 π-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.
Supervisor: Brisdon, Alan ; Pritchard, Robin Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Palladium ; Rhodium ; Gold ; Synthesis and Characterisation ; Catalysis ; Fluorine ; N-Heterocyclic Carbenes