POTASSIUM LANTHANOID CARBONATES, KM(CO3)( 2) (M = ND, GD, DY, HO, YB)

The ternary potassium lanthanoid carbonates KM(CO3)(2) (M = Nd, Gd, Dy , Ho, Yb) are obtained as single crystals by high-pressure synthesis i n steel autoclaves with carbon dioxide (starting pressure approximatel y 50 bar at ambient temperature) in the presence of water from a mixtu re of K2CO3 and MCl3 . xH(2)O (x = 7 and 6, respectively) at 450 degre es C within 4 weeks. In KNd(CO3)(2) (orthorhombic, Pmn2(1), Z = 4, a = 973.1(2), b = 645.69(8), c = 855.58(14) pm, R-1 = 0.0763 for all data ) [Nd-mu(1)-(CO3)(3)-mu(2)-(CO3)(3)] polyhedra are connected three-dim ensionally to [Nd(CO3)] layers as similarly in UO2(CO3); these layers are connected via the second half of the carbonate ligands and K+ ions . In KDy(CO3)(2) (monoclinic, C2/c, Z = 4, a = 853.8(2), b = 949.1(1), c = 694.5(1) pm, beta = 111.1(2)degrees, R-1 = 0.0266 for all data) a nd in the isotypic carbonates KM(CO3)2 (M = Gd, Ho, Yb) the polyhedra [Dy-mu(1)-(CO3)(4)-mu(2)-(CO3)(2)] and [K-mu(1)-(CO3)(6)] are connecte d to ''syndiotactic'' zig-zag chains and by further O-ligator atoms of the carbonate ligands such that each zig-zag chain is surrounded by f our unlike chains and vice versa.