The results show that the DEE and THF adducts of calcium
tetrahydroaluminate can be prepared by ball milling under
inert conditions or by mechanically assisted wet-chemical
synthesis. For each process, the same metathesis reaction 2
can be applied. After separation from the byproduct by digesttion
or Soxhlet extraction, the organic solvent can be removmoved
almost completely in a drying procedure under vacuum
at elevated temperatures. Thus, gram amounts of calcium
tetrahydroaluminate with a purity of >90% are obtained.
Of the alkaline-earth-metal tetrahydroaluminates, the
lighter Mg(AlH4)2 exhibits a sheet structure consisting of
octahedrally coordinated Mg atoms interconnected by tetrahedral
[AlH4] groups.3 BaAlH5 as the next heavier compound
after calcium tetrahydroaluminate contains onedimensional
zigzag chains of distorted [AlH6] octahedra.12
Sr2AlD7 structurally contains edge-sharing [DSr4] tetrahedra
as well as isolated [AlD6] octahedra.13 In the case of calcium
tetrahydroaluminate, IR data and the mass balance, including
the impurities, such as NaCl and residual organic solvent,
suggest a compound with the composition of Ca(AlH4)2
similar to Mg(AlH4)2. The IR data did not indicate any
formation of a hexahydride or pentahydride structure.
Moreover, a partial decomposition would be required for the
formation of a pentahydride from the isolated Ca(AlH4)2â4THF
according to