High‐Resolution Photoelectron Imaging of IrB3−: Observation of a π‐Aromatic B3+ Ring Coordinated to a Transition Metal

Joseph Czekner, Brown University
Ling Fung Chueng, Brown University
G. Stephen Kocheril, Brown University
Makism Kulichenko, Utah State University
Alexander I. Boldyrev, Utah State University
Lai-Sheng Wang, Brown University


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.