Flattening of a Curved-Surface Buckybowl (Corannulene) by η⁶ Coordination to {Cp*Ru}⁺

The corannulene complex [Cp*Ru( η 6 -C 20 H 10 )] + ( 3 +; where Cp* = η 5 -C 5 Me 5 ), prepared by the reaction of [Cp*Ru( μ 3 -Cl)] 4 with Ag + and the curved-surface buckybowl C 20 H 10 ( 1 ), has a structure in which the bowl is slightly flattened as compared with the case for free corannulene. The corannulene unit in [(Cp*Ru) 2 ( μ 2 - η 6: η 6 -C 20 H 10 )][PF 6 ] 2 ( 4 [PF 6 ] 2 ), containing two η 6 -{Cp*Ru} + units coordinated on opposite sides of the corannulene, is flattened substantially more. The X-ray-determined structure of the corresponding SbF 6 - salt, [(Cp*Ru) 2 ( μ 2 - η 6: η 6 -C 20 H 10 )][SbF 6 ] 2 ( 4 [SbF 6 ] 2 ), shows that the corannulene bowl is almost completely flat. Low-temperature NMR studies of the analogous 1,2,5,6-tetramethylcorannulene complex [(Cp*Ru) 2 ( μ 2 - η 6: η 6 -C 20 H 6 Me 4 )] 2+ ( 6 2+ ) show that there is a very low barrier to inversion of the bowl, even at −90 °C. Computational investigations reproduce the major structural features of 3 + and 4 2+ and account for the low corannulene inversion barrier in 4 2+ .