Polymeric Ferrocene and Ruthenocene Compounds with Boron in the Main Chain

Abstract

The action of phenylboron dichloride upon ferrocene or ruthenocene in highly concentrated sulfolane solution in the presence of zinc chloride produces soluble polymeric metallocene compounds having phenylboron bridging units in the backbone. Number-average molecular weights are in the approximate range 1200-3500. The polymer structures, which comprise homo- and heteroannularly disubstituted metallocene units and variable populations of cyclo-pentylene groups in addition to phenylboron bridges, arise as a result of competitive reactions believed to involve electrophilic attack by boron on the metallocene and cleavage of the bonds connecting the central Fe or Ru atom with the cyclopentadienyl rings of the metallocene system, this cleavage reaction being followed by polyalkylation steps via intermediary cyclopentenyl cations. The ruthenocene system undergoes metal-ring bond fisson more sluggishly than does ferrocene; hence, the ruthenium-containing polymers possess a lower content of cyclopentylene moieties than determined for the iron-containing counterparts obtained under comparable conditions.