High‐Resolution Photoelectron Imaging of IrB3−: Observation of a π‐Aromatic B3+ Ring Coordinated to a Transition Metal
In a high‐resolution photoelectron imaging and theoretical study of the IrB3− cluster, two isomers were observed experimentally with electron affinities (EAs) of 1.3147(8) and 1.937(4) eV. Quantum calculations revealed two nearly degenerate isomers competing for the global minimum, both with a B3 ring coordinated with the Ir atom. The isomer with the higher EA consists of a B3 ring with a bridge‐bonded Ir atom (Cs , 2A′), and the second isomer features a tetrahedral structure (C3v , 2A1). The neutral tetrahedral structure was predicted to be considerably more stable than all other isomers. Chemical bonding analysis showed that the neutral C3v isomer involves significant covalent Ir−B bonding and weak ionic bonding with charge transfer from B3 to Ir, and can be viewed as an Ir–(η3‐B3+) complex. This study provides the first example of a boron‐to‐metal charge‐transfer complex and evidence of a π‐aromatic B3+ ring coordinated to a transition metal.