College of Chemistry, Dalian University of Technology, Dalian 116023, P. R. China.
Dalton Trans. 2018 Jul 10;47(27):9079-9089. doi: 10.1039/c8dt00389k.
Six novel organic-inorganic hybrid polyoxometalate derivatives, K[(H2O)4(3-Hpic)2Ce][(H2O)5(3-Hpic)2Ce][PW10Ti2O40]·11H2O 1, K[(H2O)4(3-Hpic)2Nd][(H2O)5(3-Hpic)2Nd][PW10Ti2O40]·12H2O 2, K[(H2O)4(3-Hpic)2Sm][(H2O)5(3-Hpic)2Sm][PW10Ti2O40]·8H2O 3, H[(H2O)7(4-Hpic)La][(4-Hpic)2LaPW11O39]·14.5H2O 4, H[(H2O)7(4-Hpic)Ce][(4-Hpic)2CePW11O39]·7.5H2O 5, and K(4-Hpic)0.5[(H2O)6(4-Hpic)Nd][(4-Hpic)2NdPW11O39]·10H2O 6, (3-Hpic = 3-picolinic acid; 4-Hpic = 4-picolinic acid) have been synthesized and characterized by elemental analysis, IR, solid state UV-vis spectroscopy, thermal gravimetric analysis, powder X-ray diffraction and single-crystal X-ray diffraction. Isostructural compounds 1-3 are hybrid dimers that consist of two Ti-substituted Keggin-type polyoxoanions [PW10Ti2O40]7- and four Ln-3-Hpic coordination groups. The strong hydrogen bonds in 1-3 can make these dimers yield a 1D supramolecular chain. Compounds 4-6 are also dimers constructed from two lanthanide-substituted Keggin-type polyoxoanions [PW11LnO39]4- and four 4-Hpic ligands, which are further linked by two Ln-4-Hpic groups to form a bi-supporting structure. Then these subunits are joined together by strong hydrogen-bonding interactions between polyoxoanions and coordinated water molecules to produce a 2D supramolecular framework. All these compounds as heterogeneous Lewis acid-base catalysts show high activity and high selectivity for the cyanosilylation of different carbonyl compounds under solvent-free conditions, and can be recycled without any obvious inactivation.
六种新型有机-无机杂化多金属氧酸盐衍生物，K[(H2O)4(3-Hpic)2Ce][(H2O)5(3-Hpic)2Ce][PW10Ti2O40]·11H2O 1、K[(H2O)4(3-Hpic)2Nd][(H2O)5(3-Hpic)2Nd][PW10Ti2O40]·12H2O 2、K[(H2O)4(3-Hpic)2Sm][(H2O)5(3-Hpic)2Sm][PW10Ti2O40]·8H2O 3、H[(H2O)7(4-Hpic)La][(4-Hpic)2LaPW11O39]·14.5H2O 4、H[(H2O)7(4-Hpic)Ce][(4-Hpic)2CePW11O39]·7.5H2O 5 和 K(4-Hpic)0.5[(H2O)6(4-Hpic)Nd][(4-Hpic)2NdPW11O39]·10H2O 6（3-Hpic = 3-吡啶甲酸；4-Hpic = 4-吡啶甲酸）已通过元素分析、IR、固态 UV-vis 光谱、热重分析、粉末 X 射线衍射和单晶 X 射线衍射进行了合成和表征。同构化合物 1-3 是由两个 Ti 取代的 Keggin 型多氧阴离子[PW10Ti2O40]7-和四个 Ln-3-Hpic 配位基团组成的混合二聚体。1-3 中的强氢键可以使这些二聚体产生一维超分子链。化合物 4-6 也是由两个镧系取代的 Keggin 型多氧阴离子[PW11LnO39]4-和四个 4-Hpic 配体组成的二聚体，它们通过两个 Ln-4-Hpic 基团进一步连接，形成双支撑结构。然后，这些亚基通过多氧阴离子和配位水分子之间的强氢键相互作用连接在一起，形成二维超分子骨架。所有这些化合物作为多相路易斯酸碱催化剂，在无溶剂条件下对不同羰基化合物的氰硅烷化反应表现出高活性和高选择性，并且可以在没有明显失活的情况下回收利用。
