Trihapto Ligation of a Borirene to a Single Metal Atom: A Heterocyclic Analogue of the η3-Cyclopropenyl Ligand

The first example of a complex containing an η3‐coordinated borirene ligand bound to a single metal atom was prepared by photolytic transfer of an arylborylene ligand to diphenylacetylene and loss of three CO ligands from the precursor. The η3‐borirene complex possesses a chromium(0) atom which is also bound to one phenyl group in an η6 fashion. The complex was isolated in 15 % yield along with the corresponding metal‐free borirene, which was isolated in 62 % yield. The bonding between the chromium center and the borirene ring was studied computationally by DFT methods. A borirene provides the­ ansa: The photolytic transfer of an arylborylene fragment from a bulky arylborylene complex to diphenylacetylene and loss of three CO ligands from the precursor resulted in the first complex containing an η3‐coordinated borirene ligand bound to a single metal atom (see scheme). Like its more electron‐rich and π‐stabilized amino/organometallic counterparts, an aryl‐substituted borylene ligand can be transferred from a transition‐metal borylene.