A precise low-temperature crystal structure of Bis(cyclopentadienyl)beryllium

Abstract

The crystal structure of bis(cyclopentadienyl)beryllium has been redetermined at 128(3) K. The crystals are monoclinic, space group P2₁/n, with unit cell a 5.993(5), b 7.478(4), c 8.978(5)Å, β 85.94(6)º, and Z 2. The essential 'slip-sandwich' structure previously reported is confirmed. The beryllium is disordered between two equivalent sites. In each site it is centrally bonded to one ring and peripherally bonded to the other. There is a small alternation in the C-C distances in the crystallographically equivalent rings towards a cyclopentadiene geometry. From the bond lengths and angles the peripherally bonded cyclopentadienyl ring appears to be bonded to the beryllium with a largely sp² hybridized carbon. This indicates only a small perturbation of the delocalized π-electron structure of the cyclopentadienyl ring and accounts for the reported Raman spectrum of the compound.