abstract
The reaction of [MoO2Cl2(bipy)] (1) (bipy = 2,2'-bipyridine) with water in a Teflon-lined stainless steel autoclave (100 degrees C, 19 h), in an open reflux system with oil bath heating (12 h) or in a microwave synthesis system (120 degrees C, 4 h), gave the molybdenum oxide/bipyridine hybrid material {[MoO3(bipy)][MoO3(H2O)]}(n) (2) as a microcrystalline powder in yields of 72-92%. The crystal structure of 2 determined from synchrotron X-ray powder diffraction data is composed of two distinct neutral one-dimensional polymers: an organic-inorganic polymer, [MoO3(bipy)](n), and a purely inorganic chain, [MoO3(H2O)](n), which are interconnected by O-H center dot center dot center dot O hydrogen bonding interactions. Compound 2 is a moderately active, stable, and selective catalyst for the epoxidation of cis-cyclooctene at 55 degrees C with tert-butylhydroperoxide (tBuOOH, 5.5 M in decane or 70% aqueous) as the oxidant. Biphasic solid-liquid or triphasic solid-organic-aqueous mixtures are formed, and 1,2-epoxycyclooctane is the only reaction product. When n-hexane is employed as a cosolvent and tBuOOH(decane) is the oxidant, the catalytic reaction is heterogeneous in nature, and the solid catalyst can be recycled and reused without a loss of activity. For comparison, the catalytic performance of the precursor 1 was also investigated. The IR spectra of solids recovered after catalysis indicate that 1 transforms into the organic-inorganic polymer [MoO3(bipy)] when the oxidant is tBuOOH(decane) and compound 2 when the oxidant is 70% aqueous tBuOOH.
keywords
TERT-BUTYL HYDROPEROXIDE; BOND-VALENCE PARAMETERS; DIFFRACTION BEAM LINE; CRYSTAL-STRUCTURES; OLEFIN EPOXIDATION; DIOXOMOLYBDENUM(VI) COMPLEXES; HYDROTHERMAL SYNTHESIS; DICHOTOMY METHOD; LEWIS-BASE; OXIDES
subject category
Chemistry
authors
Abrantes, M; Amarante, TR; Antunes, MM; Gago, S; Paz, FAA; Margiolaki, I; Rodrigues, AE; Pillinger, M; Valente, AA; Goncalves, IS
our authors
Anabela Tavares Aguiar Valente
Principal Researcher
Filipe Alexandre Almeida Paz
Principal Researcher
Isabel Maria de Sousa Gonçalves
Associate Professor
Maria Margarida Feitor Pintão Moreno Antunes
Junior Researcher
Martyn Pillinger
Principal ResearcherProjects
acknowledgements
The authors are grateful to the Portuguese Science Foundation (FCT), POCI 2010, OE, and FEDER for funding through the projects PTDC/QUI/65427/2006, PTDC/QUI/71198/2006, and PTDC/QUI-QUI/098098/2008. M.M.A. and S.G. thank the FCT for Ph.D. and postdoctoral grants, respectively. We acknowledge the European Synchrotron Radiation Facility (Grenoble, France) for granting access time to the ID31 beamline.