Pyracenebis(imidazolylidene): A New Janus-Type Biscarbene and Its Coordination to Rhodium and Iridium

A pyracene-linked bis-azolium compound has been obtained
from the
bis-annulation of tetrakis­(iminopyracene) (TIP) with chloromethyl
methyl ether. The resulting bis-azolium salt was readily coordinated
to rhodium and iridium, affording bis-NHC complexes with 2-fold symmetry.
The X-ray structural characterization of the Rh complex containing
the pyracenebis­(imidazolylidene) ligand is also reported. The new
bis-NHC ligand consists of two linearly opposed (Janus-type) imidazolylidenes
annulated to both sides of a pyracene skeleton.