abstract
Treatment of the solvent adduct [MoO2Cl2(THF)(2)] with the ligand 2-(1-pentyl-3-pyrazolyl)pyridine (1, abbreviated as pent-pp) gave the dioxomolybdenum(VI) complex [MoO2Cl2(pent-pp)] (2), which was characterised by elemental analysis, H-1 NMR, FT-IR spectroscopy and single crystal X-ray diffraction (XRD). Reaction of 2 with water in a Teflon-lined stainless steel autoclave at 100 degrees C led to the isolation of a molybdenum oxide/pyrazolylpyridine hybrid material with the composition [Mo2O6(pent-pp)] (3), which was characterised by variable temperature powder XRD, scanning electron microscopy, thermogravimetric analysis, FT-IR and C-13{H-1} CP MAS NMR spectroscopies. Compounds 2 and 3 display high activity and selectivity when used as (pre) catalysts for the epoxidation of cis-cyclooctene at 55 degrees C with tert-butylhydroperoxide as an oxidant. Further catalytic experiments with 3 as a (pre) catalyst were performed using the bio-derived olefins DL-limonene (Lim) and methyl oleate (Ole). The reaction of Lim gave mainly 1,2-epoxy-p-menth-8-ene and 1,2; 8,9-diepoxy-p-menthane in a combined yield of 93% at 97% conversion (6 h), while the reaction of Ole led to 9,10-epoxystearate as the main product in 78% yield at 82% conversion (6 h). The catalytic reactions are homogeneous in nature. Starting with material 3, the oxodiperoxo complex [MoO(O-2)(2)(pent-pp)] (4) was isolated from solution after a catalytic run, suggesting that it is formed from 3 and plays a catalytic role.
keywords
CAMBRIDGE STRUCTURAL DATABASE; BOND-VALENCE PARAMETERS; CRYSTAL-STRUCTURE; DIOXOMOLYBDENUM(VI) COMPLEXES; CYCLOOCTENE EPOXIDATION; MOLYBDENUM(VI) COMPLEX; HYDROTHERMAL SYNTHESIS; EFFICIENT CATALYSTS; ORGANIC-SYNTHESIS; DIOXO COMPLEXES
subject category
Chemistry
authors
Amarante, TR; Neves, P; Paz, FAA; Valente, AA; Pillinger, M; Goncalves, IS
our authors
Anabela Tavares Aguiar Valente
Principal Researcher
Filipe Alexandre Almeida Paz
Principal Researcher
Isabel Maria de Sousa Gonçalves
Associate Professor
Martyn Pillinger
Principal Researcher
Patrícia dos Santos Neves
Assistant Researcher
Tatiana Ribau Amarante
Junior Researcheracknowledgements
We are grateful to the Fundacao para a Ciencia e a Tecnologia (FCT, project ref. PTDC/EQU-EQU/121677/2010), QREN, FEDER, COMPETE, the European Union (EU), and the Associate Laboratory CICECO (PEst-C/CTM/LA0011/2013) for continued support and funding. The NMR spectrometers are part of the National NMR Network (REDE/1517/RMN/2005), supported by POCI 2010 and the FCT. The FCT is acknowledged for financial support towards the purchase of the single-crystal diffractometer. We thank the FCT and the EU for a post-doctoral grant to P.N. (SFRH/BPD/73540/2010) cofunded by MCTES and the European Social Fund through the program POPH of QREN, and for a PhD grant to T. R. A. (SFRH/BD/64224/2009).