Knowledge Bank

The infrared spectra of matrix isolated monomeric $AlCl2$ as well as $Al2Cl6$ in the region $130cm-1$---$800cm-1$, as well as the ultraviolet spectrum of the monomer have been observed. For the monomer all four fundamentals are observed including the symmetric stretch. One is thus forced to the surprising conclusion that $AlCl3$ is pyramidal. The known thermodynamic properties of gaseous $AlCl3$ are also consistent with a pyramidal structure. The electronic structure of pyramidal $AlCl3$ will be discussed.