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Metal Silicate and Phosphate Nanomaterials
Published in Sanjay V. Malhotra, B. L. V. Prasad, Jordi Fraxedas, Molecular Materials, 2017
Pratap Vishnoi, Ramaswamy Murugavel
The solid-state pyrolysis of 7 at 500 °C affords low surface area (22 m2g−1) titania–silica nanoparticles of TiO2·4SiO2 (7a) with an average diameter of ca. 25 nm (Figure 7.2).11 The xerogels (7b) obtained from the solution-phase thermolysis of 7 show much higher surface area (552 m2g−1 for samples heated to 500 °C) and smaller primary particles (≤ca. 5 nm). The supercritical drying of the wet gel 7b in CO2 affords an aerogel (7c) morphologically similar to the xerogels and a slightly higher surface area (677 m2g−1 for samples heated to 500 °C). Complex 7 serves as a homogeneous catalyst for the selective epoxidation of cyclohexene to cyclohexene oxide using cumene hydroperoxide (CHP). The aerogel 7c shows superior catalytic performance in olefin epoxidation. Subsequently, various related complexes (tBuO)3TiOSi(OtBu)3 (9), iPrOTi[OSi(OtBu)3]3 (10), (iPrO)2Ti[OSi(OtBu)3]2 (11), and (tBuO)Ti[OSi(OtBu)3]3 (12) have also been reported and their thermal decomposition behavior has been explored.10,12,13 The related dinuclear complex [(tBuO)2Ti{μ-O2Si[OSi(OtBu)3]2}]2 (13) has been isolated via the reaction of Ti(OtBu)4 with 1 equivalent of (OH)2Si[OSi(OtBu)3]2 in pentane (Figure 7.3).14 Solid-state pyrolysis of 9, 10, and 11 in air results in the formation of crystalline TiO2–SiO2 at 600 °C–650 °C, 700 °C–750 °C, and 800 °C–850 °C, respectively. The thermolysis of 13 yields TiO2·3SiO2, which is highly active and selective for the epoxidation of cyclohexene into cyclohexene oxide using cumene hydroperoxide.
A carboxylate-bridged Mn(II) compound with 6-methylanthranilate/bipy: oxidation of alcohols/alkenes and catalase-like activity
Published in Journal of Coordination Chemistry, 2018
Yalcin Kilic, Serkan Bolat, Ibrahim Kani
In the Mn(II)/TBHP/olefin/CH3CN catalytic system, we observed that the most effective among the studied alcohols is cinnamyl alcohol, while cyclohexene is the most reactive among the studied alkenes. The compound has the highest activity for the oxidation of cyclohexene, which is an electron-rich alkene; on the other hand, the catalyst has relatively low activity for the electron-deficient alkene, ethylbenzene. The compound oxidized cyclohexene to cyclohexanone (79.3%) (total conv. 92.8% in 3 h) and other products – 2-cyclohexen-1-ol (1.7%), cyclohexene oxide (4.9%), and 1,2-cyclohexanediol (6.9%) – based on the total yield of products (total conv. 92.8% in 3 h, Table 3). The rapid reaction reached a total conversion of 22.2% at 1 min (TOF: 3556 h−1) and a total conversion of 92.8% within 3 h (TOF = 243 h−1) (Figure 2). Ethyl benzene oxidation shows the slowest kinetic profile among the other olefins (Figure 2). Acetophenone was detected in the oxidation of ethylbenzene (18.9% total conv. in 6 h).