Oxidation-Resistant Metallocenes. The Preparation and Reactions of Decachloroferrocene and Decachlororuthenocene

In order to obtain stable metallocenes, suitable for development into metal-containing polymers, resistant to oxidizing environments, the synthesis and reactions of the previously unreported class of perhalometallocenes was investigated. The detailed preparation of the first oxidation-stable metallocene, perchloroferrocene, i.e., 1,1',2,2',3,3',4,4',5,5'- decachloroferrocene (I), by a stepwise metalation-exchange halogenation process, with and without ('direct') isolation of polychlorinated intermediates, is reported. The use of the 'direct' route was extended to the synthesis of perchlororuthenocene (II) which was obtained from ruthenocene in six repetitive metalation chlorination steps. Both I and II were found to be readily metalated by n-butyllithium in tetra-hydrofuran at low temperatures to yield the corresponding 1,1'-dilithio derivatives. The versatility of these derivatives, as well as their precursors, for preparing other perchlorometallocenes, and particularly heteroannular difunctional monomers, is described.