An X-ray analysis shows 2,7-di-t-butylpyrene to be triclinic with a=9.004, b= 6"138, c=9.153/~,, ~= 96.9 °, fl= 109.1 °, and y= 108-3 °. There is one molecule in the cell. Intensity data were collected with a semi-automatic diffractometer. All atoms, including hydrogen, were located and the final R value obtained was 0.068 for 1369 reflexions.

The preparation of a stable salt of the pentathiazyl ion, S5N5+, is described; the ion has been shown by X-ray diffraction to be a planar, heart-shaped ring.