SULFATES AND HYDROGENSULFATES OF ERBIUM - ER(HSO4)(3)-I, ER(HSO4)(3)-II, ER(SO4)(HSO4), AND ER-2(SO4)(3)

Rod shaped light pink crystals of Er(HSO4)(3)-I (orthorhombic, Pbca, a =1195.0(1)pm, b=949.30(7)pm, c = 1644.3(1) pm) grow from a solution of Er-2(SO4)(3) in cone. H2SO4 at 250 degrees C. From slightly diluted s olutions (85%) which contain Na2SO4, brick shaped light pink crystals of Er(HSO4)(3)-II (monoclinic, P2(1)/n, n=520.00(5)pm, b= 1357.8(1) pm , c = 1233.4(1) pm, beta= 92.13(1)degrees) were obtained at 250 degree s C and crystals of the same colour of Er(SO4)(HSO4) (monoclinic, P21/ n, a=545.62(6)pm, b=1075.6(1) pm, c=1053.1(1) pm; beta=104.58(1)degree s) at 60 degrees C. In both hydrogen-sulfates, is surrounded by eight oxygen atoms. In Er(HSO4)(3)-I layers of HSO4- groups are connected on ly via hydrogen bridges, while Er(HSO4)(3)-II consists of a threedimen sional polyhedra network. In the crystal structure of Er(SO4)(HSO4) Er 3+ is sevenfold coordinated by oxygen atoms, which belong to four SO42 -- and three HSO4-(-)tetrahedra, respectively. The anhydrous sulfate, Er-2(SO4)(3), cannot be prepared from H2SO4 solutions but crystallizes from a NaCl-melt. The coordination number of Er3+ in Er-2(SO4)(3) (or thorhombic, Pbcn, a=1270.9(1)pm, b=913.01(7)pm, c = 921.67(7) pm) is s ix. The octahedral coordinationpolyhedra are connected via all vertice s to the SO42--tetrahedra.