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

authors	Nogueira, LS; Antunes, MM; Gomes, AC; Cunha-Silva, L; Pillinger, M; Lopes, AD; Valente, AA; Goncalves, IS
nationality	International
journal	DALTON TRANSACTIONS
keywords	CAMBRIDGE STRUCTURAL DATABASE; OXO-MOLYBDENUM COMPLEXES; CRYSTAL-STRUCTURES; EFFICIENT CATALYSTS; OXIDATION; COORDINATION; CUCURBITURIL; CYCLOHEXENE; STYRENE; EPOXIDATION
abstract	The reaction of the macrocyclic cavitand cucurbit[6]uril (CB[6]) and the diaqua complex [MoO2Cl2(H2O)(2)] in hydrochloric acid solution gave a water insoluble supramolecular compound with the general composition 2[MoO2Cl2(H2O)(2)]center dot CB[6]center dot xH(2)O center dot yHCl center dot z(CH3COCH3) (2). Single crystal X-ray diffraction (XRD) analysis revealed the presence of barrel-shape supramolecular entities, {CB[6]center dot 10(H2O)}, 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 [MoO2Cl2(H2O)(2)] molecules to form a three-dimensional (3D) framework. Compound 2 was characterised by thermogravimetric analysis (TGA), IR and Raman vibrational spectroscopy, and C-13{H-1} CP MAS NMR. The reference complex [MoO2Cl2(H2O)(2)]center dot(diglyme)(2) (1) and compound 2 were studied for the oxidative catalytic conversion of olefins (cis-cyclooctene, cyclohexene and styrene) with aqueous H2O2 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 H2O2) 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.
publisher	ROYAL SOC CHEMISTRY
issn	1477-9226
isbn	1477-9234
year published	2019
volume	48
issue	30
beginning page	11508
ending page	11519
digital object identifier (doi)	10.1039/c9dt02127b
web of science category	Chemistry, Inorganic & Nuclear
subject category	Chemistry
unique article identifier	WOS:000477957200032