Browsing by Author "Abrantes, M."
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- Application of an Indenyl Molybdenum Dicarbonyl Complex in the Isomerisation of α-Pinene Oxide to Campholenic AldehydePublication . Bruno, S.; Gomes, A. C.; Gamelas ou Carla A. Gamelas, Carla; Abrantes, M.; Oliveira, M. C.; Valente, A.; Almeida-Paz, Filipe; Pillinger, M.; Romão, C.; Gonçalves, I.The complex [{(Z5-Ind)Mo(CO)2(m-Cl)}2] (1) has been tested for the industrially relevant catalytic isomerisation of a-pinene oxide (PinOx) to campholenic aldehyde (CPA) in the liquid phase. PinOx conversion and CPA selectivity are strongly influenced by the solvent employed. Complete conversion of PinOx was achieved within 1 min at 55 1C or 30 min at 35 1C using 1,2-dichloroethane as solvent, giving CPA in 68% yield. Other products included trans-carveol, iso-pinocamphone and trans-pinocarveol. The stability of 1 under the reaction conditions used was investigated by using FT-IR spectroscopy and electrospray ionisation mass spectrometry (ESI-MS) to characterise recovered solids. In the presence of air/moisture 1 undergoes oxidative decarbonylation upon dissolution to give oxomolybdenum species that are proposed to include a tetranuclear oxomolybdenum(V) complex. Conversely, ESI-MS studies of 1 dissolved in dry acetonitrile show mononuclear species of the type [IndMo(CO)2(CH3CN)n]+. The crystal structure of the ring-slipped dicarbonyl complex [(Z3-Ind)Mo(CO)2Cl(CH3CN)2] (2) (obtained after dissolution of 1 in acetonitrile) is reported.
- Intercalation of a molybdenum eta3-allyl dicarbonyl complex in a layered double hydroxide and catalytic performance in olefin epoxidation.Publication . Gomes, A.; Bruno, S.; Gamelas ou Carla A. Gamelas, Carla; Valente, A.; Abrantes, M.; Gonçalves, I.; Romão, C.; Pillinger, M.A Zn–Al layered double hydroxide (LDH) intercalated by [Mo(η3-C3H5)Cl(CO)2(bpdc)]2− anions (bpdc = 2,2′-bipyridine-5,5′-dicarboxylate) has been prepared by coprecipitation from aqueous solution and characterised by various techniques. The one-pot method gives rise to a highly organised intercalate with an interlayer spacing of 18.3 Å and up to six (00l) basal reflections in the powder X-ray diffraction pattern. Spectroscopic studies (FT-IR, FT-Raman, 13C CP MAS NMR and UV-Vis) confirm the presence of structurally intact [Mo(η3-C3H5)Cl(CO)2(bpdc)]2− anions. The interlayer spacing of 18.3 Å indicates that the material contains a monolayer of guest anions positioned in such a way that the bpdc ligands are arranged with their longest dimension roughly perpendicular to the hydroxide layers of the host. Thermal properties were studied by thermogravimetric analysis and differential scanning calorimetry. The intracrystalline reactivity of intercalated dicarbonyl complexes was probed by using the hybrid nanocomposite as a precatalyst in the liquid phase epoxidation of cis-cyclooctene with tert-butylhydroperoxide as oxidant. Under the reaction conditions used, oxidative decarbonylation of the guest molecules takes place (with release of CO and CO2 as confirmed by on-line gas chromatography experiments) to give intercalated molybdenum oxide/bipyridine species that selectively catalyse the epoxidation reaction. The intracrystalline oxidative decarbonylation reaction is topotactic in nature.
- Use of organomolybdenum compounds for promoted hydrolysis of phosphoester bonds in aqueous mediaPublication . Gomes, A.; Gamelas ou Carla A. Gamelas, Carla; Fernandes, J.; Almeida-Paz, F.; Nunes, P.; Pillinger, M.; Gonçalves, I.; Romão, C.; Abrantes, M.The dissolution of the indenyl (Ind) complex [{(η5‐Ind)Mo(CO)2(μ‐Cl)}2] (1) in N,N′‐dimethylformamide (DMF) gives the ring‐slipped complex [(η3‐Ind)Mo(CO)2Cl(DMF)2] (2). The aerial oxidation of 2 leads to the formation of the dinuclear oxomolybdenum(V) chloride [Mo2O2(DMF)4(μ‐O)2Cl2] (3). The structures of 2 and 3·DMF have been determined by single‐crystal X‐ray diffraction. Compounds 1 and 3 were examined as promoters of phosphoester bond hydrolysis in para‐nitrophenylphosphate (pNPP), which was used as a model substrate. The reactions were performed in aqueous solution at 55 °C and followed by 1H NMR spectroscopy. For assays performed with 30–100 mol‐% of 1 or 3 relative to pNPP, both compounds promote the production of para‐nitrophenol (pNPh) from pNPP. Compound 3 is especially active in promoting the hydrolytic cleavage of the phosphoester bond (t1/2 < 80 min).