Synthesis and structures of the layered vanadyl(IV) silico-germanates Li2VO(Si1-xGex)O4 (x = 0, 0.5, 1)

The synthesis and structure determination of two new members of the oxo-metalate family, Li2VOSiO4 and Li2VOGeO4, and one intermediate compound, Li2VO(Si0.5Ge0.5)O-4, of their solid solution are presented. The structures have been determined from single-crystal X-ray diffraction. These three compounds crystallize in the tetragonal system, space group P4/nmm with a = 6.3682(6), c = 4.449(1) Angstrom for Li2VOSiO4; a = 6.4367(4), c = 4.4929(2) Angstrom for Li2VO(Si0.5Ge0.5)O-4; and a = 6.4779(1), c = 4.520(1) Angstrom for Li2VOGeO4. The general network, with two formulae per unit, is built up by parallel [VOXO4](n)(2-) layers of VO5 square pyramids sharing corners with XO4 (X = Si, Ge) tetrahedra and held together by intercalated Li cations. These compounds provide the first example of layered vanadyl(IV) silicate and germanate. (C) 1998 Elsevier Science Ltd.