Shehee Thomas C, Sykora Richard E, Ok Kang M, Halasyamani P Shiv, Albrecht-Schmitt Thomas E
Department of Chemistry, Auburn University, Auburn, Alabama 36849, USA.
Inorg Chem. 2003 Jan 27;42(2):457-62. doi: 10.1021/ic025992j.
The reactions of RE(IO3)3 [RE = Nd, Sm, Eu] with I2O5 and MoO3 in a 1:2:2 molar ratio at 200 degrees C in aqueous media provide access to RE(MoO2)(IO3)4(OH) [RE = Nd (1), Sm (2), Eu (3)] as pure phases as determined from powder X-ray diffraction data. Single crystal X-ray diffraction experiments demonstrate that these compounds are isostructural and crystallize in the chiral and polar space group P2(1). The structures are composed of three-dimensional networks formed from eight-coordinate, square antiprismatic RE3+ cations and MoO2(OH)+ moieties that are bound by bridging iodate anions. The Mo(VI) centers are present in distorted octahedral environments composed of two cis-oxo atoms, a hydroxo group, and three bridging iodate anions arranged in a fac geometry. There are four crystallographically unique iodate anions in the structures of 1-3, one of these is actually present in the form of a IO3+1 polyhedron where a short interaction of 2.285(4) A is formed between the iodate anion and the hydroxo group bound to the Mo(VI) center. This interaction results in significant distortions of the iodate anion similar to those found in tellurites with TeO3+1 units. Two of the four iodate anions are aligned along the polar b-axis, imparting the required polarity to these compounds. Second-harmonic generation (SHG) measurements on sieved powders of 1 show a response of 350 x alpha-quartz. Crystallographic data: 1, monoclinic, space group P2(1), a = 6.9383(5) A, b = 14.0279(9) A, c = 7.0397(5) A, beta = 114.890(1) degrees, Z = 2; 2, monoclinic, space group P2(1), a = 6.9243(6) A, b = 13.963(1) A, c = 7.0229(6) A, beta = 114.681(1) degrees, Z = 2; 3, monoclinic, space group P2(1), a = 6.9169(6) A, b = 13.943(1) A, c = 7.0170(6) A, beta = 114.542(1) degrees, Z = 2.
在水介质中，将摩尔比为1:2:2的RE(IO₃)₃ [RE = Nd、Sm、Eu] 与I₂O₅和MoO₃在200℃下反应，可得到纯相的RE(MoO₂)(IO₃)₄(OH) [RE = Nd (1)、Sm (2)、Eu (3)]，这是根据粉末X射线衍射数据确定的。单晶X射线衍射实验表明，这些化合物是同构的，并且在手性和极性空间群P2(1)中结晶。结构由三维网络组成，该网络由八配位的四方反棱柱形RE³⁺阳离子和通过桥连碘酸根阴离子结合的MoO₂(OH)⁺部分构成。Mo(VI)中心存在于扭曲的八面体环境中，该环境由两个顺式氧原子、一个羟基和三个呈面式几何排列的桥连碘酸根阴离子组成。在1 - 3的结构中有四个晶体学上独特的碘酸根阴离子，其中一个实际上以IO₃⁺¹多面体的形式存在，在碘酸根阴离子与与Mo(VI)中心相连的羟基之间形成了2.285(4) Å的短相互作用。这种相互作用导致碘酸根阴离子发生显著扭曲，类似于在含有TeO₃⁺¹单元的亚碲酸盐中发现的情况。四个碘酸根阴离子中的两个沿极性b轴排列，赋予这些化合物所需的极性。对1的筛分粉末进行的二次谐波产生（SHG）测量显示其响应为350×α - 石英。晶体学数据：1，单斜晶系，空间群P2(1)，a = 6.9383(5) Å，b = 14.0279(9) Å，c = 7.0397(5) Å，β = 114.890(1)°，Z = 2；2，单斜晶系，空间群P2(1)，a = 6.9243(6) Å，b = 13.963(1) Å，c = 7.0229(6) Å，β = 114.681(1)°，Z = 2；3，单斜晶系，空间群P2(1)，a = 6.9169(6) Å，b = 13.943(1) Å，c = 7.0170(6) Å，β = 114.542(1)°，Z = 2。
