School of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian 116029, China.
Dalton Trans. 2014 Apr 21;43(15):5840-6. doi: 10.1039/c3dt53023j. Epub 2014 Feb 28.
Three new inorganic-organic hybrid compounds based on Strandberg-type anions and Zn(ii)-H2biim/H2O subunits, namely {H4(H2biim)3}[Zn(H2biim)(H3biim)(H2O)(HP2Mo5O23)]2·3H2O (1), {H9(H2biim)7}[(μ-biim){(Zn(H2O)2)0.5(HP2Mo5O23)}2]·7H2O (2) and {H7(H2biim)7}[Zn(H2biim)(H2O)2(HP2Mo5O23)][H2P2Mo5O23]·8H2O (3) (H2biim = 2,2'-biimidazole), have been synthesized in aqueous solutions and characterized. They were also used as efficient and reusable catalysts for the protection of carbonyl compounds. Their fascinating structural features are that mono Zn(ii)-supporting biphosphopentamolybdate ({P2Mo5}) clusters exist in their crystal structures, and the nitrogen donor ligand H2biim exhibits three different coordination modes in these three compounds, respectively: for 1, two 2,2'-biimidazole molecules, as mono- and bidentate ligands coordinate to the same Zn(ii) ion; for 2, one bi-negative tetradentate ligand μ-biim bridges two Zn(ii) ions, while for 3, one neutral bidentate H2biim ligand links one Zn(ii) ion. Most importantly, compounds 1-3 represent the first example where Strandberg-type POMs are used as acid-catalysts in an organic reaction.
三种基于 Strandberg 型阴离子和 Zn(ii)-H2biim/H2O 单元的新型无机-有机杂化化合物，即 {H4(H2biim)3}[Zn(H2biim)(H3biim)(H2O)(HP2Mo5O23)]2·3H2O（1）、{H9(H2biim)7}[(μ-biim){(Zn(H2O)2)0.5(HP2Mo5O23)}2]·7H2O（2）和 {H7(H2biim)7}[Zn(H2biim)(H2O)2(HP2Mo5O23)][H2P2Mo5O23]·8H2O（3）（H2biim = 2,2'- 二咪唑），在水溶液中合成并进行了表征。它们还被用作保护羰基化合物的高效且可重复使用的催化剂。它们引人注目的结构特征是单 Zn(ii)-支撑双膦戊钼酸盐 ({P2Mo5}) 簇存在于它们的晶体结构中，并且氮供体配体 H2biim 在这三种化合物中分别呈现出三种不同的配位模式：对于 1，两个 2,2'- 二咪唑分子，作为单齿和双齿配体与相同的 Zn(ii) 离子配位；对于 2，一个双负离子四齿配体 μ-biim 桥接两个 Zn(ii) 离子，而对于 3，一个中性双齿 H2biim 配体连接一个 Zn(ii) 离子。最重要的是，化合物 1-3 代表了 Strandberg 型 POM 首次作为酸催化剂在有机反应中的应用实例。
