Synthese eines 2H‐Inden‐2‐on‐Dianion‐Komplexes durch Reduktion eines metallgebundenen Dicarbens

Abstract

Synthesis of a 2H‐Inden‐2‐one Complex by Reduction of a Metal‐Bound DicarbeneHerrn Professor Dr. Dr. h. c. mult. E. O. Fischer zum 75. Geburtstag gewidmet. Tetracarbonylchromium complexes with chelating o‐phenylene‐biscarbene ligands are reduced in two steps as shown by cyclic voltammetry. The first step corresponds to a reversible one‐electron transfer, the second to an irreversible one‐electron reduction followed by a rapid rearrangement of the biscarbene ligand into an η5‐bound 2H‐inden‐2‐one system by a twofold C–C coupling with one CO ligand. By reaction of tetracarbonyl[o‐phenylenebis(methoxymethylene)]chromium (4) with sodium amalgam in acetonitrile the diamagnetic tricarbonyl(η5‐1,3‐dimethoxy‐2‐indenone)chromium dianion [6]2– is formed as the final reduction product. Its structure was determined by NMR and IR spectroscopy.