Frederick N. Tebbe

Methylene exchange reactions catalyzed by alkylidene derivatives of titanium and phosphorus

Abstract Although olefin metathesis is generally catalyzed by compounds of Mo, W, or Re, alkylidene derivatives of titanium and of phosphorus also catalyze methylene exchange between olefins, the so-called degenerate metathesis reaction. In contrast to the metal-based catalysts, the phosphorus-based catalysts are effective with olefins in which the CC bond is conjugated with a functional group such as CN or COOR. These new families of catalysts may operate by an alkylidene/metallacycle mechanism like that now generally accepted for conventional olefin metatheses. The titanium system can be used to study some of the individual steps in metatheses and to help elucidate the role of the commonly used alkylaluminum cocatalyst. Titanacyclobutenes have been isolated from the reactions of acetylenes with methylenetitanium complexes. The structures have been determined crystallographically.

Some well characterized chemical reactivities of buckminsterfullerene (C60)

Abstract The metalation, halogenation and free radical addition chemistry of C 60 is described. Vibrational spectroscopy is a useful tool in assigning the structures of the products. Several underlying principles emerge for C 60 chemistry, some of which are supported by molecular orbital calculations.

Tetraneophylzirconium and its Use in the Polymerization of Olefins

Olefin polymerization catalysts based on tetraneophylzirconium and its reaction products with submicroscopic fumed alumina are discussed. (Neophyl is the 2-methyl-2-phenylp. ropyl group). Neophylzirconium aluminate or hydridozirconium aluminate supported on alumina are extremely active catalysts for high temperature (300°C) polymerization of ethylene. The high catalyst efficiency and the innocuous nate of the catalyst residues eliminate the need for deactivation or removal of the catalyst from the resultant polymer. The effect of catalyst structure on activity and oplymer properties is discussed.