A refinement of the structure of biphenylene

Abstract

Crystals of biphenylene, C12H8, are monoclinic, a= 19.728, b= 10"578, C=5"861 /~k, fl=91 ° 10', Z=6, space group P21/a.The intensities of the reflexions were measured with a scintillation counter and Cu Ke radiation, and the positional and thermal parameters of the carbon and hydrogen atoms were refined by least squares, the final R value being 0.062 for 2316 observed reflexions.The anisotropic thermal parameters of the carbon atoms were interpreted in terms of rigid-body vibrations, and the measured bond lengths were then corrected for rotational oscillation, effects.The bonds joining the six-membered rings measure 1.514+0.003A,, and the bonds in the six-membered rings, starting with the bond in the four-membered ring, measure 1.426+ 0-003, 1-372+ 0.002, 1.423 + 0.003, and 1-385 + 0.004 A,.These dimensions reinforce the conclusion that the molecule must be considered as a cyclobutane derivative.The angles in the four-membered ring are all 90 °, but those in the six-membered rings show significant deviations from 120 °.The mean C-H distance is 1.06+0.02 A. The molecule which is situated at a centre of symmetry is completely planar; the other molecule is slightly non-planar as a result of crystal packing forces.All the intermolecular C • • • C, C • • • H, and H • • • H contacts correspond to van der Waals interactions.A REFINEMENT OF THESTRUCTURE OF BIPHENYLENE Table 1. Measured and calcu&ted structure factorsEach group of three columns contains h, 10 Fo, and I0 Fc; unobserved reflexions, for which I0 Fo is listed as 0, have threshold values in the range 6-9.-1,+-122 10 i+ 13 +, .....