有机阳离子修饰的Strandberg型钼磷酸盐的合成、催化性能

以钼酸钠、联咪唑、盐酸胍及过量的磷酸在pH值34的水溶液中,自组装形成1个由联咪唑和胍修饰的Strandberg型钼磷酸盐化合物1{H₄(H₂biim)₅(C(NH₂)₃)₄}H₂P₂Mo₅O₂₃]₂·8H₂O(H₂biim=2,2'-联咪唑)。 通过X射线单晶衍射、红外光谱(FT-IR)、热重-差热 (TG-DTA)、粉末衍射(XRD)等技术手段对化合物1进行表征,确定其具有稳定的有机-无机杂化的3D结构。 将化合物1用作有机化学中酮羰基保护反应的催化剂,以环己酮缩乙二醇合成为例,分别考察了催化剂用量、物料比及反应时间对反应的影响。 确定最佳反应条件为:催化剂(以Mo计)与酮的摩尔比1:300,酮醇摩尔比1:1.4,反应时间2.5 h。 在此条件下评价了化合物1对其它4种缩酮合成的催化活性,结果表明,化合物1对环己酮缩乙二醇合成反应的催化作用最佳。

Synthesis and Catalytic Activity of a Strandberg-type Molybdophosphate Modified by Organic Cations

A Strandberg-type molybdophosphate {H₄(H₂biim)₅(C(NH₂)₃)₄}H₂P₂Mo₅O₂₃]₂·8H₂O(1, H₂biim=2,2'-biimidazole) modified by 2,2'-biimidazole and guanidinium cations was self-assembled in aqueous solution of pH=34 containing sodium molybdate, 2,2'-biimidazole, guanidine hydrochloride, and an excess of phosphoric acid, and was characterized by single crystal X-ray diffraction analysis, infrared spectroscopy(FT-IR), themogravimetry-differential thermal analysis(TG-DTA) and X-ray powder diffraction(XRD). Compound 1 has a stable 3D organic-inorganic hybrid framework. It was used as a catalyst for carbonyl-protection. The synthesis of cyclohexanone ethylene ketal was performed as an example to investigate some influence factors on the yield, such as catalyst loading, molar ratio of reactants and reaction time. The optimal conditions are: the molar ratio of catalyst(based on Mo) to ketone is 1:300, the molar ratio of ketone to alcohol is 1:1.4, and reaction time is 2.5 h. The catalytic activity of compound 1 for the synthesis of four other ketals was evaluated. The results show that compound 1 is a better catalyst for the synthesis of cyclohexanone ethylene ketal.