New transition-metal derivatives of the fullerene C60

The new compounds [M(NO)(PPh3)2(η2-C60)] (M = Co 1 or Rh 2), [RuX(NO)(PPh3)2(η2-C60)] (X = Cl 3 or H 4), [Re2H8(PMe3)4(η2: η2′-C60)] 5 and [TaH(η-C5H5)2(η2-C60)] have been prepared and characterised. Crystal structures have been determined for 3 and 5 and show typical η2 co-ordination of C60 in the former, but a rare example of η4 co-ordination in the latter. The soluble adducts 1, 2, 4, 5 and [M(CO)4(η2-C60)] (M = Ru 7 or Fe 8) have been electrochemically reversibly reduced up to the dianion and to the trianion for 4. The E° values are shifted to slightly less negative values than for C60 itself in consonance with the reduction in the number of fullerene double bonds. Addition of the electrophiles I2, maleic anhydride or PPh3 to 1 or 2 easily regenerated free C60. The presence of an isobenzofuran side chain in C60(C20H14O) prevents attack by the incoming metal centre Fe(CO)4 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(η-C5H5)2] resulting in the formation of [Pd(PPh3)2(η2-C60)] or [Co(η-C5H5)2]+[C60]–.