NHC-Gold(I) and (III) Complexes for Use in Energy Storage and Aryl Halogenation
Date
2012-05
Authors
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Publisher
University of Delaware
Abstract
N-Heterocyclic Carbene (NHC) complexes of gold(I) and gold(III) of the form
AuX(IPr) and AuXCl2(IPr) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene,
X = halide or aryl) were prepared and investigated for photochemical activity. Where
X = Cl, it was found that an energetically downhill oxidative addition could add an
equivalent of Cl2 which could then be subsequently photoreductively eliminated in an
energetically uphill step, representing a model energy storage-and-release scheme for
chemical fuel formation. Where X = aryl (fluorinated phenyl derivatives), oxidative
addition of Cl2 and subsequent reductive elimination produced the gold(I) complex
AuCl(IPr) and the chlorinated aryl ligand. The reaction pathway was strongly
dependent upon the electronics of the aryl ligand; more electron-rich ligands (X =
phenyl) preferentially underwent thermal reductive elimination, while electron-poor
ligands (X = pentafluorophenyl) could only be actuated photochemically. A gradient
between these extremes was observed in intermediate ligands (X = 4-fluorophenyl,
2,4,6-trifluorophenyl, and 2,3,5,6-tetrafluorophenyl).
Description
Keywords
N-Heterocyclic Carbene, energy storage, aryl halogenation