Two chloride silicates of yttrium: Y3Cl[SiO4](2) and Y6Cl10[Si4O12]

The chloride-poor yttrium(III) chloride silicate Y3Cl[SiO4](2) crystallizes orthorhombically (a = 685.84(4), b = 1775.23(14), c = 618.65(4) pm; Z = 4) in space group Pnma. Single crystals are obtained by the reaction Of Y2O3, YCl3 and SiO2 in the stoichiometric ratio 4:1:6 with ten times the molar a mount Of YCl3 as flux in evacuated silica tubes (7 d, 1000 degreesC) as col orless, strongly light-reflecting platelets, insensitive to air and water. The crystal structure contains isolated orthosilicate units [SiO4](4-) and comprises cationic layers {(Y2)Cl}(2+) which are alternatingly piled parall el (010) with anionic double layers {(Yl)(2)[SiO4](2)}(2-). Both crystallog raphic different Y3+ cations exhibit coordination numbers of eight. YI is s urrounded by one Cl- and 7 O2- anions as a distorted trigonal dodecahedron, whereas the coordination polyhedra around Y2 show the shape of bicapped tr igonal prisms consisting of 2 Cl- and 6 O2- anions. The chloride-rich chlor ide silicate Y6Cl10[Si4O12] crystallizes monoclinically (a= 1061,46(8), b = 1030,91(6), c = 1156,15(9) pm, beta = 103.279(8)degrees; Z = 2) in space g roup C2/m. By the reaction Of Y2O3, YCl3 and SiO2 in 2:5:6-molar ratio with the double amount Of YCl3 as flux in evacuated silica tubes (7 d, 850 degr eesC), colorless, air- and water-resistant, brittle single crystals emerge as pseudo-octagonal columns. Here also a layered structure parallel (001) w ith distinguished cationic double-layers {(Y2)(5) Cl-9}(6+) and anionic lay ers {(Y1)Cl[Si4O12]}(6-) is present. The latter ones contain discrete cyclo -tetrasilicate units [Si4O12](8-) of four cyclically corner-linked [SiO4] t etrahedra in all-ecliptical arrangement. The coordination sphere around (Y1 )(3+) (CN = 8) has the shape of a slightly distorted hexagonal bipyramid co mprising 2 Cl- and 6 O2- anions. The 5 Cl- and 2 O2- anions building the co ordination polyhedra around (Y2)31 (CN = 7) form a strongly distorted penta gonal bipyramid.