ON THE SODIUM TETRAHYDROXOALUMINATE CHLOR IDE NA2[AL(OH)4]CL

The hitherto unknown compound Na2[Al(OH)4]Cl was prepared by crystalli sation from a NaCl containing sodium aluminate solution. According to the X-ray single crystal investigation (tetragonal, space group P4/nmm , a = 7.541 angstrom, c = 5.059 angstrom, Z = 2) the compound represen ts the first example of a crystalline hydroxoaluminate with monomeric [Al(OH)4]- anions. Cl- shows a quadratic anti prismatic coordination t o 4Na+ and over hydrogen bonds to 4O2- while Na+ is octahedrally coord inated by 4O2- and 2Cl- (axial). The results of the crystal structure analysis are confirmed by Al-27 and Na-23 MAS NMR investigations. Na2[ Al(OH)4]Cl decomposes at about 200-degrees-C without intermediates und er formation of beta-NaAlO2 and NaCl.