Beryllocene

Beryllocene is an organoberyllium compound with the chemical formula Be(C 5 H 5 ) 2 , first prepared in 1959. The colorless substance can be crystallized from petroleum ether in the form of white needles at −60 °C and decomposes quickly upon contact with atmospheric oxygen and water.

Beryllocene is an organoberyllium compound with the chemical formula Be(C 5 H 5 ) 2 , first prepared in 1959. The colorless substance can be crystallized from petroleum ether in the form of white needles at −60 °C and decomposes quickly upon contact with atmospheric oxygen and water.

Structure

Beryllocene shows different molecular geometries depending on the physical state. The low-temperature X-ray structure analysis shows a slipped sandwich structure, i.e. the rings are offset from each other - one ring is η 5 coordinated with a Be-Cp distance of 152 pm, the second only η 1 coordinated (Be-Cp distance: 181 pm). The reason for the η 5 , η 1 structure is that the orbitals of beryllocene can only be occupied with a maximum of 8 valence electrons. In the gas phase both rings η 5 appear to be coordinated. In fact, one ring is significantly further from the central atom than the other (190 and 147 pm) and the apparent η 5 coordination is due to a rapid fluctuation of the bond. Based on gas-phase electron diffraction studies at 120 °C, Arne Haaland concluded in 1979 that the two rings are only about 80 pm shifted from each other and are not coordinated η 5 ,η 1 , but rather η 5 ,η 3 . Like beryllocene, the octamethyl derivative Be(C 5 Me 4 H) 2 has a slipped sandwich structure with η 5 ,η 1 coordination. In contrast Be(C 5 Me 5 ) 2 shows the classic η 5 ,η 5 coordination. In the crystal, however, the Be-C distances vary between 196.9(1) and 211.4(1) pm.

References

Text derived from https://en.wikipedia.org/w/index.php?oldid=1343683941 under CC BY-SA 4.0; modifications have been made.