Molecular Structure of Dicyclopentadienylberyllium (C5H5) 2Be

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Abstract
The molecular structure of gaseous (C5H5) 2Be has been determined from electron‐scattering data. The molecule consists of two planar, symmetrical C5H5 rings. C1–C2 = 1.424±0.002 Å and C1–H1 = 1.070±0.005 Å. The rings are parallel and staggered with a vertical ring—ring distance h = 3.37±0.03 Å. The CH skeleton thus has point group symmetry D5d. The beryllium atom may occupy two alternative positions on the fivefold rotation axis h = 1.485±0.005 Å from one ring and h2 = 1.980±0.010 Å from the other. The complete molecule thus has point group symmetry C5v. It appears then that the potential energy curve of the beryllium atom has two minima. This is readily understood from an ionic binding model. The discrepancy between the values found for h and h1+h2 is believed to be due to intramolecular motion.