2 Titanosilsesquioxane Anchored on Mesoporous Silicas. A Novel Approach for the preparation of Heterogeneous Catalysts for Selective Oxidations. Fabio Carniato, a Chiara Bisio, a Enrico Boccaleri, a Matteo Guidotti, b Elena Gavrilova b,c and Leonardo Marchese a * [a]dipartimento di Scienze e Tecnologie Avanzate and Nano-SISTEMI Interdisciplinary Centre, Università del Piemonte Orientale A. Avogadro, Via Bellini 25G, 15100, Alessandria, Italy. [b] Istituto di Scienze e Tecnologie Molecolari and IDECAT CNR Unit Via G. Venezian 21, Milano, Italy [c] Dip. Scienze Chimiche e Ambientali, Via Valleggio 11, Como, Italy [a] [b] [c] D Prof. Leonardo Marchese, Dr. Fabio Carniato, Dr. Chiara Bisio and Dr. Enrico Boccaleri Dipartimento di Scienze e Tecnologie Avanzate and Nano-SISTEMI Interdisciplinary Centre, Università del Piemonte Orientale A. Avogadro, Via Bellini 25G, 15100, Alessandria, Italy. Fax: Dr. Matteo Guidotti and Dr. Elena Gavrilova Istituto di Scienze e Tecnologie Molecolari and IDECAT CNR Unit Via G. Venezian 21, Milano, Italy Dr. Elena Gavrilova Dip. Scienze Chimiche e Ambientali, Via Valleggio 11, Como, Italy Supporting information for this article is available on the WWW under or from the author.))
3 Contents: 1. Materials 2. Characterization 3. Figures and Schemes Materials Ti-NH 2 POSS (1): 1 Ti-NH 2 POSS was prepared following two steps of reaction: i) cleavage reaction of commercial completely condensed aminopropyl heptaisobutyl-poss from Hybrid Plastics Company in order to obtain partially condensed trisilanol aminopropyl hexaisobutyl-poss; ii) corner capping reaction of partially condensed trisilanol aminopropyl hexaisobutyl-poss with titanium precursor Ti(iPrO) 4 to obtain Ti-NH 2 POSS. In detail: i) Synthesis of partially condensed trisilanol aminopropyl hexaisobutyl-poss: An equimolar solution of aqueous tetraethylammonium hydroxide (TEAOH 35% from Sigma Aldrich) and completely condensed aminopropyl heptaisobutyl-poss was prepared adding a 0.5mL of TEAOH (35 wt.%) (mol ) to a solution of POSS (1 g, mol ) in 25mL of THF under vigorous stirring. After addition, the temperature was raised to reflux and stirred for 4 h to complete the reaction. The base excess was neutralized by few ml of 2N HCl. During this phase, tetraethylammonium chloride salt (C 2 H 5 ) 4 N(Cl) was isolated and removed by the solution. Filtration of the solution through a fine sintered glass funnel, and solvent removal in vacuum, led to the formation of 600 mg of partially condensed trisilanol aminopropyl hexaisobutyl-poss product as white amorphous foam which was dissolved in Et 2 O and dried over anhydrous MgSO 4. ii) Synthesis of Ti-NH 2 POSS (1): 160 µl (mol ) of Ti(iPrO) 4 (97%, Sigma Aldrich) were added with vigorous stirring to a solution made of 400 mg (mol ) of partially condensed trisilanol aminopropyl hexaisobutyl-poss in 30 ml of chloroform. The reaction solution was previously carefully purged with nitrogen to prevent the rapid hydrolysis of Ti(iPrO) 4. After addition, the temperature was raised to 333 K and stirred for 4h30min under nitrogen flow. Subsequently, the solvent was evaporated until a white powder (300 mg) was obtained.
4 Ti-POSS-TSIPI (2): 1g of Ti-NH 2 POSS ( mol), was dissolved in 40 ml of chloroform (by Sigma Aldrich) and stirred at room temperature for few minutes. 153 µl of triethylamine and 272 µl ( mol) of 3- isocyanatopropyl triethoxysilane were added to the solution under nitrogen flow. The reaction was stirred at room temperature for 20h. Finally, the solvent was removed under vacuum until to obtain a powder product (700 mg). 1 H NMR (400 MHz) spectrum of Ti-POSS-TSIPI in CDCl 3 solvent: 3.9 ppm [2H, NH, ureic group], 3.7 ppm [6H, CH 2, OEt], 3.6 ppm [1H CH, OiPr], 2.9 [4H, CH 2 of ureic group], 1.85 ppm [6H, CH], 1.20 ppm [15H, CH 3 of OEt and OiPr groups and], 0.93 ppm [36 H, CH 3 of isobutyl groups], 0.59 ppm [20H, CH 2 ]. Characterization NMR spectrum of Ti-POSS-TSIPI (2) dissolved in CDCl3 (concentration M 0.1) at room temperature and applied to 1 H nucleus have been recorded on a Jeol Eclipse Plus spectrometer with a 8 T magnet. Infrared (IR) spectra of Ti-NH 2 POSS(1), Ti-POSS-TSIPI(2) and 3-isocyanatopropyl triethoxysilane have been recorded in KBr matrix in the range cm -1 at 4 cm -1 resolution using a Bruker Equinox 55 spectrometer. The spectra of SBA-15, SiO 2 Dav, Ti- POSS-TSIPI/SBA-15 and Ti-POSS-TSIPI/SiO 2 have been collected under vacuum conditions. X-ray diffraction (XRD) patterns were obtained on a ARL XTRA48 diffractometer using Cu Ka radiation (lambda = Å). HRTEM images were collected on a JEOL 3010 High Resolution Transmission Electron Microscope operating at 300 kv. Specimens were prepared by dispersing the sample by sonication in isopropanol and by depositing few drops of the suspension on carbon-coated grids. N 2 physisorption measurements were carried out at 77K in the relative pressure range from 1*10-6 to 1 P/P0 by using a Quantachrome Autosorb1MP/TCDinstrument. Prior to the analysis the samples were outgassed at 373K for 3 h (residual pressure lower than 10-6 Torr).
5 Apparent surface areas were determined by using Brunauer-Emmett-Teller equation, in the relative pressure range from 0.01 to 0.1 P/P0. Pore size distributions were obtained by applying both the NLDFT method (N 2 silica kernel based on a cylindrical pore model applied to the desorption branch. Catalyst Test: The catalysts (50 mg) were pre-treated at 413 K in vacuo for 12 h prior to use. Limonene (1.0 mmol; Aldrich), internal standard (1.0 mmol; mesitylene; Fluka) and the oxidant (1.2 mmol; TBHP 5.5 M in decane; Aldrich) were added to the solid in ethyl acetate (Fluka) under dry nitrogen. The reaction mixture was analysed by GC-FID and GC-MS. Titanium contents were determined by mineralization and ICP-AES elemental analysis. Schemes Scheme 1: Limonene (1-methyl-4-(prop-1-en-2-yl)cyclohex-1-ene) epoxidation with TBHP. OH + O OH Cat O OH Scheme 2: Carveol (2-methyl-5-(prop-1-en-2-yl)cyclohex-2-enol) epoxidation with TBHP.
6 Figures Figure 1: IR spectra in vacuum of A): SBA-15 (solid line) and Ti-POSS-TSIPI/SBA-15 (dashed line) and B): SiO 2 Dav (solid line) and Ti-POSS-TSIPI/SiO 2 Dav (dashed line) C (%) removal of the solid catalyst Time /h Figure 2: Heterogeneity test for Ti-POSS-TSIPI/SiO 2. Conversion profile vs. time under typical conditions (solid line) and after 1 h reaction and following removal of the solid catalyst by centrifugation (dashed line).
7 Table 1: Catalytic performance of carveol epoxidation over Ti-containing catalysts Catalyst Ti content a (wt.%) C b 24h (%) TON c after 24 h S d 24 h (%) Ti-POSS-TSIPI/SBA Ti-POSS-TSIPI/SiO 2 Dav Ti/SBA Reaction conditions: glass batch reactor; 10 ml AcOEt solvent; 358 K; 24 h; 50 mg catalyst; 1.2 mmol TBHP; 1.0 mmol carveol; mesitylene internal standard. a obtained by ICP-AES; b carveol conversion after 24 h; c Turn-over Numbers after 24 h (mol converted substrate/ mol Ti); d selectivity to endocyclic carveol monoepoxide after 24 h. References 1. F. Carniato, E. Boccaleri and L. Marchese, Dalton Trans., 2008, 36.
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