Revisiting Ir(CO)3Cl

We return to an old puzzle – the short metal–metal separation and electrical conductivity of the apparently unoxidized one-dimensionally stacked structure of a d8 Ir(I) complex, Ir(CO)3Cl. One would expect neither a short Ir–Ir distance of 2.84 Å, nor metallicity in an unoxidized stacked square-planar d8 array. We build up dimer, trimer, one-dimensional polymer and model 3-dimensional structures, in both molecular and extended structure plane wave calculations. The short Ir–Ir separation in the polymer, with a substantial contribution of 6pz–5dz26pz–5dz2 bonding to it, is obtained without any oxidation. There is computational evidence for an important level crossing in the polymer. The metallicity remains unexplained, but likely arises from partial oxidation. And that remains an outstanding experimental issue.

Graphical abstractOne would expect neither a short Ir–Ir distance of 2.84 Å, nor metallicity in an unoxidized stacked square-planar d8 array, as one sees in the structure of Ir(CO)3Cl. In calculations, a short Ir–Ir separation is obtained and explained, without any oxidation. The metallicity remains a puzzle.Figure optionsDownload full-size imageDownload as PowerPoint slide