Main-Group Metallomimetics: Transition Metal-like Photolytic CO Substitution at Boron

The carbon monoxide adduct of an
unhindered and highly reactive
CAAC-bound arylborylene, [(CAAC)­B­(CO)­Ar] (CAAC = cyclic (alkyl) (amino)­carbene),
has been prepared using a transfer reaction from the linear iron borylene
complex [(PMe3) (CO)3Fe=BAr]. [(CAAC)­B­(CO)­Ar]
is a source of the dicoordinate [(CAAC)­ArB:] borylene that can be
liberated by selective photolytic CO extrusion and that, although
highly reactive, is sufficiently long-lived to react intermolecularly.
Through trapping of the borylene generated in this manner, we present,
among others, the first metal-free borylene­(I) species containing
a nitrogen-based donor, as well as a new boron-containing radical.