The first pentahaptofullerene metal complexes

Cyclopentadienyl metal complexes have played important roles in chemistry owing to their unique structures and functional activities. Here we report the synthesis and characterization of fan entirely new class of cyclopentadienyl (Cp) metal complexes (η5-C60Ph5)MLn (MLn = Li, K, Tl, and Cu·PEt3). In these molecules, the five Cp carbons represent one pentagon of C60 isolated form the remaining 50 sp2 carbon atoms by five surrounding sp3 carbon atoms each bearing a phenyl group. The X-ray crystal structure analysis of the thallium complex. Tl(η5-C60Ph5)·2.5THF revealed it unique and esthetically pleasing C5 symmetrical molecular structure with the phenyl groups forming a chiral propeller array. The thallium atom is deeply buried in the cavity created by the phenyl groups, bonding to the five Cp carbons (η5-coordination) which an averaged Tl-C distance of 2.87 A. The key finding that we made in this research was a remarkable 5-fold addition of an organocopper reagent to C60, which stands in contrast to the monoaddition reaction of Grignard or organolithium reagents.