Nogueira Lucie S, Antunes Margarida M, Gomes Ana C, Cunha-Silva Luís, Pillinger Martyn, Lopes André D, Valente Anabela A, Gonçalves Isabel S
Department of Chemistry, CICECO - Aveiro Institute of Materials, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.
REQUIMTE/LAQV & Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, 4169-007 Porto, Portugal.
Dalton Trans. 2019 Aug 14;48(30):11508-11519. doi: 10.1039/c9dt02127b. Epub 2019 Jul 11.
The reaction of the macrocyclic cavitand cucurbit[6]uril (CB[6]) and the diaqua complex [MoOCl(HO)] in hydrochloric acid solution gave a water insoluble supramolecular compound with the general composition 2[MoOCl(HO)]·CB[6]·xHO·yHCl·z(CHCOCH) (2). Single crystal X-ray diffraction (XRD) analysis revealed the presence of barrel-shape supramolecular entities, {CB[6]·10(HO)}, aligned in layers which are shifted relative to adjacent layers to form a brick-like pattern. The CB[6]/water hydrogen-bonded entities further engage in intermolecular interactions with water, HCl and [MoOCl(HO)] molecules to form a three-dimensional (3D) framework. Compound 2 was characterised by thermogravimetric analysis (TGA), IR and Raman vibrational spectroscopy, and C{H} CP MAS NMR. The reference complex [MoOCl(HO)]·(diglyme) (1) and compound 2 were studied for the oxidative catalytic conversion of olefins (cis-cyclooctene, cyclohexene and styrene) with aqueous HO as oxidant. Using alcohols as solvents, 2 was employed in a one-pot two-stage strategy for converting olefins to alkoxy products, which involves oxidation (with HO) and acid chemistry. Mechanistic studies were carried out using different intermediates as substrates, and the type of solvent and substrate scope were investigated. The results demonstrated the ability of the CB[6]/Mo supramolecular adduct to function as an acid-oxidation multifunctional catalyst, and its recovery and reuse via relatively simple procedures.
大环穴状配体葫芦[6]脲（CB[6]）与二水合配合物[MoOCl(HO)]在盐酸溶液中的反应生成了一种水不溶性超分子化合物，其一般组成为2[MoOCl(HO)]·CB[6]·xHO·yHCl·z(CHCOCH)（2）。单晶X射线衍射（XRD）分析表明存在桶状超分子实体{CB[6]·10(HO)}，它们排列成层，这些层相对于相邻层发生位移以形成砖状图案。CB[6]/水氢键结合的实体进一步与水、HCl和[MoOCl(HO)]分子发生分子间相互作用，形成三维（3D）框架。化合物2通过热重分析（TGA）、红外和拉曼振动光谱以及C{H} CP MAS NMR进行了表征。研究了参考配合物[MoOCl(HO)]·(二甘醇二甲醚)（1）和化合物2以水相HO作为氧化剂对烯烃（顺式环辛烯、环己烯和苯乙烯）的氧化催化转化。以醇类为溶剂，2采用一锅两步策略将烯烃转化为烷氧基产物，该策略涉及氧化（用HO）和酸化学过程。使用不同的中间体作为底物进行了机理研究，并考察了溶剂类型和底物范围。结果表明CB[6]/Mo超分子加合物能够作为一种酸氧化多功能催化剂发挥作用，并且可以通过相对简单的程序进行回收和再利用。
