om500926v_si_001.pdf (226.7 kB)
Formation and Reactivity of Gold Carbene Complexes in the Gas Phase
journal contribution
posted on 2014-12-22, 00:00 authored by Christopher
A. Swift, Scott GronertA series
of ligated gold(I) carbenes (where the ligand is Ph3P,
Me2S, or an N-heterocyclic carbene, NHC) were
formed in the gas phase by a variety of methods. Gold(I) benzylidenes
could be formed using Chen’s method of dissociating an appropriate
phosphorus ylide precursor. The resulting carbene undergoes an addition
reaction with olefins to give an adduct. The adduct undergoes a second
gas-phase reaction with an olefin, where presumably a cyclopropanation
product is displaced by the second olefin molecule. Both steps in
the process were analyzed with linear free energy relationships (i.e.,
Hammett plots). Under collision-induced dissociation conditions, the
adduct undergoes competing processes: (1) dissociation of the cyclopropanation
product to give ligated gold(I) species and (2) metathesis to give
a more stable gold(I) carbene. Attempts to form less stable gold(I)
carbenes in the gas phase by Chen’s approach or by reactions
of diazo species with the ligated gold(I) cations were not successfulprocesses
other than carbene formation are preferred or the desired carbene,
after formation, rearranges rapidly to a more stable species. In accord
with other recent work, the data suggest that coordination to a ligated
gold(I) cation in the gas phase may not offer sufficient stabilization
to carbenes to prevent competition from rearrangement processes.