Identification of cyano dianions of C-60 by electrospray mass spectrometry

We have observed three dianions of cyano-adducted buckminsterfullerene, namely C-60(CN)(2)(2-), C-60(CN)(4)(2-) and C-60(CN)(6)(2-), in the negative-ion electrospray mass spectrometry (EMS) of freshly prepared solutions of C-60 and NaCN. The results of semi-empirical calculations show that the dianions are likely to have radically different geometries to those preferred by the corresponding neutral molecules. So while C-60(CN)(6) exhibits the same structure as C60Cl6, its dianion C-60(CN)(6)(2-) has a preferred geometry in which CN- and (CN)(5)(-) groups are located on opposite sides of the C-60 sphere.