Host-Guest Chemistry and Catalysis of Layered Metal Hydroxides with Hydrotalcite Structure

对于层状金属氢氧化物的主-客体化学，考察了同多阴离子或金属卤化物阴离子插入氢氧化物层间的情况。以层状双氢氧化物（Mg_2Al（OH）_6NO_3）为例，通过阴离子交换法将十钒酸根阴离子插入到层间通道中，并通过XRD和IR技术研究了热处理过程中同聚阴离子的化学转化。同聚阴离子是稳定的，只有高达473 K，转化为较小的物种。在573 - 623 K下焙烧，生成[ -VO 3- ]_3 ~（-+）型聚合钒酸盐<n->。整体分层结构保持高达623 K。在623-673 K时，基质层转变为MgO结构。在873 K左右，钒酸盐与基质氧化物反应生成α-Mg 2 V2 O 7。热处理也导致部分V（V）还原为V（IV），金属卤化物如NiCl_4 ~<2->+可插入氢氧化物层间。插层的阴离子可以与烷基溴如丁基溴进行卤化物交换。电子光谱研究表明，NiCl_4^-<2->阴离子具有四面体对称性，在卤代交换反应后仍保持四面体对称性，溴离子与Ni阳离子配位.在层状金属氢氧化物催化下，考察了Cl^-或NiCl_4^<2->-插层氢氧化物对烷基氯与烷基溴卤代交换反应的催化能力.使用这些氢氧化物，可以容易地合成烷基溴如苄基溴。还考察了溶剂和烷基种类对反应速率的影响。

As to the host-guest chemistry of layered metal hydroxide, intercalation of isopolyanions or metal-halide anions into the interlayer of the hydroxide was examined. For example, decavanadate anions were intercalated by anion exchange into the interlayer gallery of a layered double hydroxide (Mg_2Al(OH)_6NO_3) and the chemical transformation of the isopolyanions by thermal treatment was examined by XRD and IR techniques. The isopolyanions are stable only up to 473 K and transformed into smaller species. The calcination at 573 - 623 K leads to the formation of polymeric vanadate of the type [ -VO3- ]_3^<n->. The overall layered structure is maintained up to 623 K. At 623-673 K, the host layers are turned into a MgO structure. The vanadate reacts with the host oxide to form alpha-Mg_2V_2O_7 around 873 K. Thermal treatment also results in the reduction of part of V(V) to V(IV) species as indicated by ESR.Metal-halide anions such as NiCl_4^<2-> can intercalate into the interlayer of the hydroxide. The anions intercalated can undergo a halide exchange with alkyl bromides such as butyl bromide. Electronic spectrum study showed that the NiCl_4^<2-> anion has tetrahedral symmetry and that the symmetry is retained even after the halide-exchange reaction, the bromide anions being coordinated to Ni cations.On the catalysis of layered metal hydroxide, the catalytic ability of the Cl^-- or NiCl_4^<2->-intercalated hydroxide to a halide-exchange reaction between alkyl chloride and alkyl bromide was examined. Using these hydroxides, alkyl bromides such as benzyl bromide can be easily synthesized. The effect of solvent and of the kind of alkyl group on the rate of the reaction was also examined.