New transition-metal derivatives of the fullerene C60

The new compounds [M(NO)(PPh3)(2)(eta(2)-C-60)] (M = Co 1 or Ph 2), [RuX(NO)(PPh3)(2)(eta(2)-C-60)] (X = Cl 3 Or H 4), [Re2H8(PMe3)(4)(eta(2):eta(2)-C-60)] 5 and [TaH(eta-C5H5)(2)(eta(2)-C-60)] have been prepared and characterised. Crystal structures have been determined for 3 and 5 and show typical eta(2) co-ordination of C-60 in the former, but a rare example of eta(4) co-ordination in the latter. The soluble adducts 1, 2, 4, 5 and [M(CO)(4)(eta(2)-C-60)] (M = Ru 7 or Fe 8) have been electrochemically reversibly reduced up to the dianion and to the trianion for 4. The E degrees values are shifted to slightly less negative values than for C-60 itself in consonance with the reduction in the number of fullerene double bonds. Addition of the electrophiles I-2, maleic anhydride or PPh3 to 1 or 2 easily regenerated free C-60. The presence of an isobenzofuran side chain in C-60(C20H14O) prevents attack by the incoming metal centre Fe(CO), at adjacent double bonds and results in inequivalency of the remaining double bonds and a mixture of regioisomeric products. However, the isobenzofuran side chain may be displaced by Pd(PPh3)(2) or [Co(eta-C5H5)(2)]resulting in the formation of [Pd(PPh3)(2)(eta(2)-C-60)] or [Co(eta-C5H5)(2)](+)[C-60](-).