Novel Mixed-Valence Heteropolyoxometalates: A Molybdenum Diphosphonate Anion [Mo^V₇Mo^VIO₁₆(O₃PPhPO₃H)₄]^3- and Its One- and Two-Dimensional Assemblies

A novel mixed-valence polyoxomolybdenum anion, [MoV7MoVIO16(O3PPhPO3H)4]3-, was synthesized hydrothermally from molybdenum oxide, molybdenum metal, boric and phosphoric acids, 1,2-phenyldiphosphonic acid, and imidazole (ImH) and was structurally characterized as an imidazolium salt (orthorhombic, Aba2; a = 16.674(4), b = 17.238(1), and c = 24.81(2) Å). One- and two-dimensional structures of this anion and additional molybdenum diphosphonate linkers were assembled as well. They were structurally characterized as their pyridinium (pyH) salts (pyH)4[{MoV7MoVIO16(O3PPhPO3)2(O3PPhPO3H)2}{Mo2O4(OH)(HO3PPhPO3H)}]·5H2O (monoclinic, P21/c; a = 20.8506(9), b = 22.866(1), and c = 21.1403(9) Å; β = 118.7087(8)°) and (pyH)3[{MoV7MoVIO16(O3PPhPO3)4}{Mo2O2(OH)2(HO3PPhPO3H)}]·3H2O (orthorhombic, Pca21; a = 19.057(1), b = 20.402(2), and c = 20.660(2) Å). The compounds were also characterized by IR spectroscopy and magnetic measurements.本研究以氧化钼、金属钼、硼酸、磷酸、1,2-苯二膦酸以及咪唑(ImH)为原料，通过水热法合成了一种新型混合价态多钼氧阴离子[MoV7MoVIO16(O3PPhPO3H)4]3-，并将其制备为咪唑鎓盐进行结构表征：该晶体属正交晶系，空间群为Aba2，晶胞参数a=16.674(4), b=17.238(1), c=24.81(2) Å。该阴离子与额外的钼基二膦酸酯连接基可组装得到一维及二维结构，同样以吡啶鎓(pyH)盐形式完成结构表征，对应化合物分别为：(pyH)4[{MoV7MoVIO16(O3PPhPO3)2(O3PPhPO3H)2}{Mo2O4(OH)(HO3PPhPO3H)}]·5H2O（单斜晶系，空间群P21/c，晶胞参数a=20.8506(9), b=22.866(1), c=21.1403(9) Å, β=118.7087(8)°）与(pyH)3[{MoV7MoVIO16(O3PPhPO3)4}{Mo2O2(OH)2(HO3PPhPO3H)}]·3H2O（正交晶系，空间群Pca21，晶胞参数a=19.057(1), b=20.402(2), c=20.660(2) Å）。上述化合物还通过红外光谱与磁学测试完成了表征。