SIGMA-CYCLOPENTADIENYLIRON DERIVATIVES AS INTEREMDIATES IN FORMATION OF FERRICENIUM CHLORIDE AND FERROCENE

Di-σ-cyclopentadienyliron chloride monotetrahydrofuranate (2) was prepared from the reaction of sodium cyclopentadienide and iron(III) chloride in a 2:1 molar ratio at –80° in tetrahydrofuran (THF). This compound (2) is stable either as a yellow solid at –80° or in THF solution at room temperature. Above –50° or upon the addition of organic solvents, such as ether or n-pentane, 2 rearranges to a blue solid, ferricenium chloride. Tris-σ-cyclopentadienyliron (3) was not isolated from the reaction of sodium cyclopentadienide and iron(III) chloride in a 3:1 molar ratio in THF. However, studies on periodic hydrolysis of each reaction mixture (2:1 or 3:1) at – 80° and room temperature establish that 3 is an intermediate in the formation of ferrocene (1). © 1969, American Chemical Society. All rights reserved.