Abstract: | X-Ray Investigations and Structure Chemistry of Chalkogenomolybdates and - tungstates. I. Crystallographic data of compounds of the type A2MeX4, A2MeOX3, and A2MeO2X2 (A = K, NH , Rb, Cs; (Me = Mo, W; X = S, Se) are discussed and general trends are illustrated. The molybdates and tungstates A2MeX4 and A2MeOX3 (A = K, NH , Rb, Cs; X = S, Se) crystallize in the rhombic space group D ? Pnma. The compounds (NH4)2MeO2X2 (Me = Mo, W; X = S, Se) crystallize in the monoclinic space group C ? C2/c. |