Boron cluster anions containing multiple B12 icosahedra

We report a mass spectrometric study of boron cluster anions (Bn−, n=7–55) produced by laser vaporization from two different types of boron-containing sample rods, one composed of YB66 and the other, pure boron. In mass spectra recorded from the YB66 sample, we observed a repeating intensity pattern of boron cluster anions having local maxima at (B13−)(B12)0,2,3 as well as at B26−. Similar phenomena were not observed with a pure boron sample. We attribute these observations to the structural differences between the two materials, and in particular to the (B12)(B12)12 super-icosahedral structure of crystalline YB66.