title: Beryllium chloride
text: # Beryllium chloride
  
  Beryllium chloride is an inorganic compound with the formula $BeCl_2.$ It is a colourless, hygroscopic solid that dissolves well in many polar solvents. Its properties are similar to those of aluminium chloride, due to beryllium's diagonal relationship with aluminium.
  
  ## Structure and synthesis
  
  Beryllium chloride is prepared by reaction of the metal with chlorine at high temperatures:
  
      Be + $Cl_2$ → $BeCl_2$
  
  $BeCl_2$ can also be prepared by carbothermal reduction of beryllium oxide in the presence of chlorine. $BeCl_2$ can be prepared by treating beryllium with hydrogen chloride.
  
  Two forms (polymorphs) of $BeCl_2$ are known. Both structures consist tetrahedral $Be^{2+}$ centers interconnected by doubly bridging chloride ligands. One form consist of edge-sharing polytetrahedra. The other form resembles zinc iodide with interconnected adamantane-like cages. In contrast, $BeF_2$ is a 3-dimensional polymer, with a structure akin to that of quartz.
  
  In the gas phase, $BeCl_2$ exists both as a linear monomer and a bridged dimer with two bridging chlorine atoms where the beryllium atom is 3-coordinate. The linear shape of the monomeric form is as predicted by VSEPR theory. The linear shape contrasts with the monomeric forms of some of the dihalides of the heavier members of group 2, e.g. $CaF_2,$ $SrF_2,$ $BaF_2,$ $SrCl_2,$ $BaCl_2,$ $BaBr_2,$ and $BaI_2,$ which are all non-linear. Beryllium chloride dissolves to give tetrahedral $[Be(OH_2)_4]^{2+}$ ion in aqueous solutions as confirmed by vibrational spectroscopy.
  
  ## Reactions
  
  Beryllium chloride forms a tetrahydrate, $BeCl_2•4H_2O$ $([Be(H_2O)_4]Cl_2).$ $BeCl_2$ is also soluble in some ethers.
  
  ## Applications
  
  Beryllium chloride is used as a raw material for the electrolysis of beryllium, and as a catalyst for Friedel-Crafts reactions.
  
  