Action of ammonium fluoride on scandium: Synthesis and crystal structures of (NH4)(3)[ScF6] and [Cu(NH3)(4)](3)[ScF6](2)

The action of (NH4)F on scandium in copper ampoules yields either (NH4)(3)[ ScF6] or ScF3 and a small quantity of [Cu(NH3)(4)](3)[ScF6](2), respectivel y, depending upon the molar ratio of the educts (NH4)F:Sc (6:1 and 4:1, res pectively) and temperature. (NH4)(3)[ScF6] crystallizes with the cryolite t ype of structure: monoclinic, P2(1)/n, Z = 2; a = 650.0(2); b = 651.4(2); c = 949.0(2) pm; beta = 90.40(2)degrees, [Cu(NH3)(4)](3)[ScF6](2) is triclin ic, P-1, Z = 1; a = 821.1(2); b = 821.2(2); c = 822.7(2) pm; alpha = 90.04( 3); beta = 90.00(3); gamma = 90.16(3)degrees. In its chemical behaviour aga inst (NH4)F, scandium parallels aluminium rather than gallium.