STEREOCHEMICAL PATTERNS FORMED BY ADDITION TO FULLERENE C-60

A combined theoretical and experimental approach is used to recognize the sterochemical patterns which emerge when X(2) (X=H, halogen, etc.) is added to C-60 to form C(60)X(n), and the patterns formed by rings which incorporate carbon atoms of the fullerene, C-60(ring)(n). Additi on to form C(60)X(2) occurs either at an edge linking two hexagonal fa ces on C-60, or across the para-positions of one of the hexagonal face s. Further addition occurs to produce potentially a very great number of isomers, but in some cases at least the pattern emerging is relativ ely simple. An important feature is the tendency of hexagonal faces wi th low degrees of addition, for example C6H2 or C6Br, to add further g roups to form C6H4 or C6Br2 for example. This feature results in the p roduction of chains, formed by the edge sharing of these hexagonal fac es, which progressively increase in length as the extent of addition i ncreases. Particularly stable structures are formed if these chains el iminate the chain ends to form cyclic structures. Examples include the skew pentagonal pyramids in C(60)X(6), C(60)X(12) and C(60)X(18), the crowns in C(60)X(18) and C(60)X(36), and the rhombicuboctahedral patt ern in C(60)X(24). The ring compounds C-60(ring)(1-6), formed by addit ions to hex-hex edges, have rings occupying octahedral sites about the C-60.