Novel Bismethanofullerenes and Ethenofullerene from the Reaction of Propiolates with C(60) in the Presence of Triphenylphosphine.

Methyl propiolate reacts with C(60) in the presence of triphenylphosphine in toluene to give a bismethanofullerene 2. Compound 2 is an adduct of two methyl propiolate units to a C(60) moiety and consists of two methano bridges across two 6,6-ring junctions of the same six-membered ring on the fullerene moiety. Similarly, ethyl propiolate reacts with C(60) in the presence of PPh(3) to yield bismethanofullerene 3. Detailed analysis of the products from the reaction of methyl propiolate with C(60) shows, in addition to 2 and C(60), an ethenofullerene 4 and an unidentified insoluble material were isolated. Compound 4, which may be viewed as a [2 + 2] cycloaddition adduct of C(60) and methyl propiolate, consists of a cyclobutene ring fused to the carbons on a 6,6-ring junction of the C(60) moiety. On the basis of the known chemistry of phosphine with electron-withdrawing alkynes and C(60), mechanisms are proposed to account for the formation of the bismethanofullerenes 2 and 3 and ethenofullerene 4.