Half-Sandwich Metal Carbonyl Complexes as Precursors to Functional Materials: From a Near-Infrared-Absorbing Dye to a Single-Molecule Magnet

Chemical oxidations of piano-stool chromium/cobalt carbonyl complexes Cr­(CO)3(η6,η5-C6H5C5H4)­Co­(CO)2 (1) and Cr­(CO)3(η6,η6-C6H5C6H5) Cr­(CO)3 (2) were investigated. Upon one-electron oxidation, 1 was transformed to a heterometalloradical species, 1•+. However, either one- or two-electron oxidation of 2 afforded a decomposition product, 3. Dipping 3 into pentane led to the formation of 4 via a crystal-to-crystyal transformation with the removal of solvent molecules. Complexes 1•+ and 4 were fully characterized by various spectroscopic techniques and single-crystal X-ray analysis. Cation 1•+ features a weak Cr–Co bond with a Wiberg bond order of 0.278. A near-infrared absorption band around 1031 nm was observed for 1•+, which is far red-shifted in comparison to previously reported dinuclear metalloradical species. Complex 4 contains a chromium­(II) with a distorted pyramidal geometry and displays single-molecule magnetic properties.