The new Neodymium(III) oxide chloride Oxoselenate(IV) Nd_7O _5Cl_3 [SeO_3]_4 [Das neue Neodym(III)-Oxidchlorid-Oxoselenat(IV) Nd_7O _5Cl_3[SeO_3]_4]

摘要

Pale violet, needle-shaped single crystals of the new neodymium(III) oxide chloride oxoselenate(IV) Nd_7O_5Cl_3[SeO _3]_4 were obtained by the reaction of Nd_2O _3 and NdCl_3 with SeO_2 (molar ratio: 3:1:4) in evacuated silica ampoules within seven days at 775°C, if an excess of CsCl worked as fluxing agent. Nd_7O_5Cl_3[SeO _3]_4 crystallizes in the triclinic space group P1? with the lattice parameters a = 694.46(4), b = 944.53(5), c = 1567.92(9) pm, α = 87.821(3), β = 81.849(3), γ = 84.852(3)° and Z= 2. Its structure exhibits seven crystallographically different Nd~(3+) cations, of which (Nd1)~(3+) - (Nd4)~(3+) are coordinated by O ~(2-) anions forming distorted square prisms. The polyhedra of (Nd1)~(3+) and (Nd2)~(3+) receive additional caps by one Cl~- anion each, and (Nd5)~(3+) - (Nd7)~(3+) show mixed square antiprismatic environments of O~(2-) and Cl~- anions too. However, the polyhedra of (Nd5)~(3+) and (Nd6)~(3+) include two, the polyhedron about (Nd7)~(3+) even three Cl~- anions, Two-dimensional ~2_∞{[O_5Nd _7]~(11+)} layers of edge- and vertex-linked [ONd ~4]~(10+) tetrahedra are built up by (O1)~(2-) - (O5)~(2-) together with all Nd~(3+) cations. All the other oxygen atoms belong to four crystallographically different Se~(4+) cations erecting ψ~1-tetrahedral oxoselenate(IV) units [SeO _3]~(2-) with stereochemically active non-bonding electron pairs ("lone pairs") pointing into the free space between the ~2_∞{[O_5Nd_7]~(11+)} layers. Three independent Cl~- anions in threefold coordination of Nd~(3+) cations interconnect the ~2_∞([O _5Nd_7][SeO_3]_4)~(3+)} layers to form a three-dimensional network, thereby achieving the charge balance.