A hydrogen-bonded assembly of cucurbit[6]uril and [MoO2Cl2(H2O)2] with catalytic efficacy for the one-pot conversion of olefins to alkoxy products. Issue 30 (11th July 2019)

• Record Type: Journal Article
• Authors: Nogueira, Lucie S.; Antunes, Margarida M.; Gomes, Ana C.; Cunha-Silva, Luís; Pillinger, Martyn; Lopes, André D.; Valente, Anabela A.; Gonçalves, Isabel S.
• Is Part Of: Dalton transactions. Volume 48:Issue 30(2019)
• Page Start: 11508
• Page End: 11519
• Publication Date: 2019-07-11
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c9dt02127b
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : A supramolecular cucurbit[6]uril/Mo VI hydrogen-bonded assembly displays dual-function (oxidation/acid) catalytic behavior for the one-pot conversion of olefins to alkoxy products. Abstract : The reaction of the macrocyclic cavitand cucurbit[6]uril (CB[6]) and the diaqua complex [MoO2 Cl2 (H2 O)2 ] in hydrochloric acid solution gave a water insoluble supramolecular compound with the general composition 2[MoO2 Cl2 (H2 O)2 ]·CB[6]· x H2 O· y HCl· z (CH3 COCH3 ) (2 ). Single crystal X-ray diffraction (XRD) analysis revealed the presence of barrel-shape supramolecular entities, {CB[6]·10(H2 O)}, 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 [MoO2 Cl2 (H2 O)2 ] molecules to form a three-dimensional (3D) framework. Compound2 was characterised by thermogravimetric analysis (TGA), IR and Raman vibrational spectroscopy, and 13 C{ 1 H} CP MAS NMR. The reference complex [MoO2 Cl2 (H2 O)2 ]·(diglyme)2 (1 ) and compound2 were studied for the oxidative catalytic conversion of olefins ( cis -cyclooctene, cyclohexene and styrene) with aqueous H2 O2 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 H2 O2 ) 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 VI supramolecular adduct to function as an acid-oxidation multifunctional catalyst, and its recovery and reuse via relatively simple procedures.