New transition-metal derivatives of the fullerene C60

Abstract

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: η^2′-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]^–.