In the last twenty years, alkene and alkyne activation by gold catalysts has received
considerable attention. Most of the applications of gold catalysts have concerned the
addition of nitrogen‐ and oxygen‐nucleophiles to the C‐C multiple bond. Metal‐mediated
olefin oxidation is still a subject of great interest for a number of researchers. Various classes
of mechanisms have been envisaged for different metal systems. Among these, that one
involving metallaoxetanes (1‐metalla‐2‐oxacyclobutanes), as key intermediates in the
oxygen‐transfer reaction, has been recently corroborated by a number of experimental
evidences.
The synthesis of a series of gold(III) oxo complexes, [Au2(N,N)2(μ‐O)2][PF6]2, supported by
bidentate 6‐substituted‐2,2’‐bipyridines, has been the main subject of this thesis. The
oxygen atom transfer reaction to olefins from these unusual gold(III) complexes has been
thoroughly studied. The reaction with styrene, chosen as a model, was studied first and an
unprecedented gold(I) olefin complex of the type [Au(N,N)(η2‐CH2=CHPh][PF6] structurally
characterized. Styrene oxygenated derivatives, contemporaneously formed, were identified
as well. Analogous results have been successively obtained with other terminal olefins, while
no reaction takes place with internal olefins. Although not isolated, formation of the olefin
complexes and of the oxygenated species was attributed to the decomposition of an
oxametallacyclic intermediate. Successively, from the reactions with cyclic alkenes, in
particular norbornene, evidence for such intermediates was gained by the isolation and
structural characterization of the unprecedented oxaauracyclobutane [Au(bipyMe)(κ2‐O,C‐2‐
oxynorbornyl)][PF6] and the gold(I) alkene complexes [Au(bipyR)(η2‐alkene)][PF6] (R = Me,
alkene = norbornene). A plausible mechanism for the formation of these species, involving
eliminative reduction reaction, was inferred by the reaction of the auraoxetane with excess
norbornene: indeed, the gold(I) olefin complex and exo‐2,3‐epoxynorbornane were
obtained.
Structural and spectroscopic data of the new alkene complexes [Au(bipyR)(η2‐alkene)][PF6]
and [Au2(bipyR)2(μ−η2,η2‐dialkene)][PF6]2 were collected and thoroughly analyzed. On the
whole, they suggested an extent π‐back‐donation contribution to the olefin‐gold bond and
this was corroborated of the theoretical calculations carried out at hybrid‐DFT level on the
model compound [Au(bipy)(η2‐CH2=CH2)]+.
A further insight into the structural features and electronic properties of these still rare gold
derivatives can be of interest as for the design of new gold catalysts