Cadmium(I) tetrachloroaluminate
# Cadmium(I) tetrachloroaluminate

Cadmium(I) tetrachloroaluminate is the inorganic compound with the formula $Cd_2[AlCl_4]_2,$ a tetrachloroaluminate of cadmium(I). It was the first compound reported (1961) that contained cadmium in the +1 oxidation state and features a cadmium–cadmium bond.

## Preparation and properties

$Cd_2[AlCl_4]_2$ was originally prepared by dissolving Cd metal in molten $CdCl_2$ followed by the addition of $AlCl_3.$

    $CdCl_2$ + Cd → $Cd_2Cl_2$
    $Cd_2Cl_2$ + 2 $AlCl_3$ → $Cd_2[AlCl_4]_2$

Subsequent studies of the Raman vibrational spectrum indicated the presence of a cadmium–cadmium bond, which was confirmed by two separate X-ray diffraction studies of single crystals. The compound can therefore be compared to mercury(I) (mercurous) compounds (such as mercury(I) chloride), which contain Hg2+2. The Cd−Cd single bonds are part of ethane-like $Cd_2Cl_6$ units sharing vertices with $AlCl_4$ units, with a Cd−Cd bond length reported as 257.6 pm or 256.1pm.

$Cd_2[AlCl_4]_2$ is diamagnetic. It contains no unpaired electrons and reacts readily with water disproportionating to give Cd metal and $Cd^{2+}.$

