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Synthesis of substituted (N,C) and (N,C,C) Au() complexes: the influence of sterics and electronics on cyclometalation reactions
Ist Teil von
Dalton transactions : an international journal of inorganic chemistry, 2022-03, Vol.51 (13), p.582-597
Ort / Verlag
England: Royal Society of Chemistry
Erscheinungsjahr
2022
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
Cyclometalated Au(
iii
) complexes are of interest due to their catalytic, medicinal, and photophysical properties. Herein, we describe the synthesis of derivatives of the type (N,C)Au(OAc
F
)
2
(OAc
F
= trifluoroacetate) and (N,C,C)AuOAc
F
by a cyclometalation route, where (N,C) and (N,C,C) are chelating 2-arylpyridine ligands. The scope of the synthesis is explored by substituting the 2-arylpyridine core with electron donor or acceptor substituents at one or both rings. Notably, a variety of functionalized Au(
iii
) complexes can be obtained in one step from the corresponding ligand and Au(OAc)
3
, eliminating the need for organomercury intermediates, which is commonly reported for similar syntheses. The influence of substituents in the ligand backbone on the resulting complexes was assessed using DFT calculations,
15
N NMR spectroscopy and single-crystal X-ray diffraction analysis. A correlation between the electronic properties of the (N,C) ligands and their ability to undergo cyclometalation was found from experimental studies combined with natural charge analysis, suggesting the cyclometalation at Au(
iii
) to take place
via
an electrophilic aromatic substitution-type mechanism. The formation of Au(
iii
) pincer complexes from tridentate (N,C,C) ligands was investigated by synthesis and DFT calculations, in order to assess the feasibility of C(sp
3
)-H bond activation as a synthetic pathway to (N,C,C) cyclometalated Au(
iii
) complexes. It was found that C(sp
3
)-H bond activation is feasible for ligands containing different alkyl groups (isopropyl and ethyl), although the C-H activation is less energetically favored compared to a ligand containing
tert
-butyl groups.
Cyclometalated (N,C) and (N,C,C) Au(
iii
) complexes were synthesised
via
a robust microwave-assisted protocol.