Synthesis and Crystal Structure of Nd_2Si_2O_7 in Low Temperature Form

The title compound was obtained by high temperature solid state reaction and flux method. The crystal belongs to tetragonal system, space group P41, withcell dimensions a= 6. 738(2), c= 24. 532 (3) A, V= 1113. 8(3) A 3, Z= 8, Mr =456. 65, Dc= 5. 45 g/cm3, F(000) = 1632, μ= 189. 3 cm-1. R=0.052, Rw=0. 059.The structure consists of isolated Si2O7 double tetrahedra which are arranged in layersperpendicular to the c axis. Four crystallographically different rare earth atoms in oneunit cell are located on each side of the layers and connect the four nearest SiO4 tetrahedra to form a three-dimensional network structure.

Synthesis and Crystal Structure of Gd_3(BsiO_6) (SiO_4)

The title compound Gd3BSi2O10 crystallizes in orthorhombic system,space group Pbca, with dimensions of a= 9. 630(1), b= 6. 959(1), c= 22. 792(3) A,V= 1527. 4(4) A 3, Z=8, Mr= 698. 73, Dc= 6.08 g/cm3, F(000) =2440, p= 262.5 cm-1, R=0. 047,,Rw=0. 053, based on 3750 with I≥3. 0 1(I) observed independent reflections. The structure contains two kinds of isolated anions: (BSi (1)O6)5- and(Si(2)O4)4- independently forming isolated sheets arranged alternately along the c axis. The Polyhedra of three crystallographically independent rare earth atoms Gd (1),Gd (2), Gd(3) are connected through edges-shared each other to form a three dimensional network structure.

Synthesis and Structureof［（C_2H_5）_4N］［Mo_3（μ_3－O）（μ－Cl）_3（μ－CH_3CH_2COO）_3Cl_3］

The title cluster compound, Mo_3Cl_6O_7NC_17H)35, has been synthesized reaction of a mixture of MoC_l3·3H_2O、(C_3H_5)_4NI and CH_3CH_2COOH. Crystallographic data: monoclinic, space group P2_1/a, a=12. 990 (2), b=19. 572 (5), c =12. 411 (3)A, β=90. 00(4)°, V=3155. 3 A￣3, Z=4, M_r=866. 01, D_c= 1. 823 g/cm￣3. μ(MoKα)=16. 934, MoKα(λ=0. 71073 A ), T= 295K , F(000)=1712, final R=0. 048 and R_w= 0. 062 for 2997 reflections with I≥3σ(I). The crystal contains discrete cations and anions. The mono-oxo-capped trinuclear Mo cluster anion consists of three Cl atoms and three CH_3CH_2COO- groups that bridge the three edges of Mo triangle,and three terminal Cl atoms. The coordination around Mo is distortedly octahedral.

Synthesis and Crystal Structure of Er_2Si_2O_7

The title compound crystallizes in monoclinic system, space group C2/m with cell dimensions of a=6. 843(2), b=8. 939(2), c=4. 720(1) A, β=101. 77(2), V=282. 7A3, Z=2, Mr=502. 69, Dc=5' 91 g·cm-3, u(MoKa)=303. 0cm-1, F(000) ~ 440. The structure solution and refinement are based on 869 uniqueobserved reflections with I≥3(I) and the final discrepancy factors converged at R=0. 034, Rw= 0. 042. The structure is considered to be the oxygen atoms packed innearly hexagonal arrangement with rare earth atoms in the octahedral and silicon atomsin tetrahedral holes in alternately parallel layers.

Synthesis and Crystal Structure of Trigadolinium Bromoorthosilicate，Gd_3Br（SiO_4）_2

Crystals of a new lanthanide orthosilicate, Gd_3Br(SiO_4)_2 (M_r=735.82) were prepared by solid state reaction from the GdOBr/V/NH_4Br system at 900℃. The ammonium bromide served as transport gas. The title compound crystallizes on orthorhombic, space group Imma with a=6.960(3), b=18. 176(6), c=6. 284(2) A ; V=794. 9(5) A￣3; Z=4; D_c=6. 12 g/cm￣3 F(000)=1276; μ(MoKα)=301.63cm￣(-1). A full-matrix least-squares structure factors refined with the 484 observed reflections with I>3. 0σ (I) and anisotropic thermal parameters for the Gd atoms gave R=0.061 and R_w=0. 064 respectively. The gadolinium atoms are in two sites and 8-coordinated as GdO_6Br_2 and GdO_7Br bicapped trigonal prism. The Gd(2) atom is disordered and distributed systematically among two I-lattice related(81) positions, the distance between these positions is 1.599 A. The presence of the bromine atoms causes some long Gd - O bonds. The silicon atoms were extracted from the quartz tube.