New routes toward metallated methanofullerene terdentate bisaminoaryl ligands

The preparation of a series of new ligands, comprising a NCN ligand (C6H2(CH2NMe2)2-2,6-X-4, X=H, Br, I) substituted on the para position with a [1,2]-methanofullerene group is described. Metallation of these ligands is achieved via an oxidative addition reaction of nickel(0) or palladium(0) complexes. The first step of this reaction comprises the formation of a π-complex between the metal center and the fullerene moiety of the ligand, which upon heating in a subsequent step is followed by oxidative addition of the NCN–halide bond to the metal center. The nickel(II) complex C60C(Me)NCN·NiBr (9) was isolated in pure form. Low temperature NMR spectroscopy and theoretical calculations showed that the NCN moiety in 9 rotates about the (Me)CNCN bond at room temperature. UV–Vis spectroscopic measurements of 9 suggest that binding a metal center via a covalent metal–carbon bond to the NCN moiety does not lead to a substantial change in the electronic structure of the fullerene moiety. The cyclo voltammograms of 9 showed the absence of a Ni(II)/Ni(III) oxidation/reduction process, while the second and fourth C60 reduction potentials were anodically shifted.