A Simple Method for Preparing Metallocenes

Abstract

Many sorts of metallocenes have already been synthesized in various methods by many investigators. However, only a one-step method for the preparation of ferrocene has been proposed 1) this method consists of a direct reaction between ferric chloride and cyclopentadiene in the presence of an organic base, without the reduction procedure of ferric chloride to ferrous chloride. No simple and convenient method for the direct preparation of metal-locenes other than ferrocene has yet been reported. The present authors wish to report on a simple method for the preparation of such metallocenes as cobaltocene and nickelocene as well as of ferrocene. They can be synthesized in good yields by this convenient procedure. The reactions of ferric chloride, cobaltous chloride, and nickel chloride with cyclopen-tadiene were carried out in the presence of an excess of diethylamine. The yields of metal-locenes were 84% for ferrocene, 28% for cobaltocene, and 66% for nickelocene. In this procedure the formation of the metallocenes is considered to proceed through the following mechanism : by the reaction of the metal chloride and diethylamine, a corresponding ammine-complex salt of the metal is formed, and the complex salt reacts with cyclopen-tadiene, which has previously been de-proto-nated by strongly basic diethylamine.2)