A theoretical study of transition metal complexes of C60 and C70 and their ring-opened alternatives

Ring opened structures of C60 and C70 are shown to be stabilized by complexation with transition metal fragments of the form CnHnM, where n = 3 to 6 and M = Cr, Mn, Fe, Co, and Rh. The ring opening of C60 and C70 is compared with the reverse process of the well-known catalytic conversion of acetylene into benzene. Calculations at the semi-empirical PM3(tm) level show that the 6-membered ring in C60 and C70 can be opened up in different ways through complexation with transition metal fragment. The mode of ring opening depends on the number of external 5- and 6-membered rings around the 6-membered ring being cleaved. The structures and energetics of the various ring-opened structures are discussed.