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 temperature range from –70 °C to +20 °C that one-electron electrochemical reduction of (⁶-C¹³H¹⁰)Cr(CO)₃ (1) to the corresponding 19-electron anion radical (1 ^–) is accompanied by splitting off of a H atom to form the 18-electron carbon-centered anion (⁶-C₁₃H₉)Cr(CO)₃ (^–2 ), which at room temperature undergoes intramolecular haptotropic isomerization to the metal-centered (⁵-C₁₃H₉)Cr(CO)₃ ^– (^– 3) anion. The reversible one-electron reduction of3 ^– to the corresponding 19-electron radical dianion3 ^2.– induces ^{5 6} interannular isomerization. In contrast to the equilibrium shift to the ⁵-isomer in 18-electron complexes 2 and 3, in their 19-electron analogs the equilibrium is shifted to the ⁶-isomer.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 48–53, January, 1994.This work was carried out with financial support from the Russian Foundation for Basic Research (no. 93-03-5209)