ELECTRON-TRANSFER-INDUCED CHANGE OF DIRECTION OF INTERANNULAR HAPTOTROPIC ISOMERIZATION OF FLUORENYLTRICARBONYLCHROMIUM ANIONS

It has been shown by cyclic voltammetry in a THF medium in the tempera ture range from -70 degrees C to +20 degrees C that one-electron elect rochemical reduction of (eta(6)-C13H10)Cr(CO)(3) (1) to the correspond ing 19-electron anion radical (1(-)) is accompanied by splitting off o f a H atom to form the 18-electron carbon-centered anion (eta(6)-C13H9 )Cr(CO)(3)(-) ((-)2), which at room temperature undergoes intramolecul ar haptotropic isomerization to the metal-centered (eta(5)-C13H9)Cr(CO )(3)(-) ((-)3) anion. The reversible one-electron reduction of 3(-) to the corresponding 19-electron radical dianion 3(2.-) induces eta(5)-- >eta(6) interannular isomerization. In contrast to the equilibrium shi ft to the eta(5)-isomer in 18-electron complexes 2 and 3, in their 19- electron analogs the equilibrium is shifted to the eta(6)-isomer.