Binuclear Cage‐Like Copper(II) Silsesquioxane (“Cooling Tower”) – Its High Catalytic Activity in the Oxidation of Benzene and Alcohols

Abstract

A new method of metallasilsesquioxane synthesis is described for the first time. According to this method, a partial nucleophilic cleavage of polymeric copper phenylsilsesquioxane by the use of sym-cis-tetraphenylcyclotetrasiloxanolate nonaethanolate (1) gave previously unknown binuclear cage-like copper silsesquioxane [(PhSiO 1.5 ) 10 (CuO) 2 (NaO 0.5 ) 2 ·

New Trends in Oxidative Functionalization of Carbon–Hydrogen Bonds: A Review

“…Polynuclear metal complexes containing voluminous organic [63,66,118,119,[129][130][131]186,[213][214][215][216][217][218][234][235][236][237][238][239][240][241] or siloxane [221][222][223][224][225][226][227][228] ligands are also very efficient in oxidations of organic compounds including saturated hydrocarbons with peroxides. For example, dinuclear copper complex 11 [221,224] and hexairon complex 15 (for the structure, see Figure 9) affording the products of cyclohexane oxidation in a very high yield of 46% (see Figure 10 [226]) can be considered as "inorganic models of methane monooxygenases."…”

“…For example, dinuclear copper complex 11 [221,224] and hexairon complex 15 (for the structure, see Figure 9) affording the products of cyclohexane oxidation in a very high yield of 46% (see Figure 10 [226]) can be considered as "inorganic models of methane monooxygenases." These enzymes contain dinuclear copper [317,318] and iron [319] reaction centers, respectively.…”

“…This approach modeling natural enzymes can be called biomimetic route. Various polynuclear complexes [320][321][322] including siloxane derivatives [221][222][223][224][225][226][227][228] containing bulky ligands are especially attractive as catalysts in oxidations with peroxides. Bulky ligands around the reaction centers give rise in these cases to the selectivity enhancement [12,323].…”

“…The most simple compound is the binuclear cage-like copper silsesquioxane [(PhSiO 1.5 ) 10 (CuO) 2 (NaO 0.5 ) 2 4EtOH] (complex 11) with a "Cooling Tower" structure ( Figure 5) [221]. In addition, isomers containing four [222] and six [223] copper ions have been isolated.…”

Alkali-Metal-Directed Hydrolytic Condensation of 3-Mercaptopropyltrimethoxysilane

“…The most popular method for preparation of cyclic siloxane monomers is hydrolytic condensation of trialkoxyorganosilanes (Scheme 1) in the presence of water and an alkali metal hydroxide. It was found that properties of metal cations can influence the structure of the formed moieties since they work as template centers and structural elements helping to bind siloxane bonds into cyclic organosiloxanolate fragments [20][21][22][23][24][25][26][27][28][29][30][31][32]. While transition or rare-earth metal cations lead to the formation of varied-size (n=4 [20], 5 [21], 6, 8, 12 [22][23][24]) cyclic species, sodium and potassium cations enable the synthesis of small cyclosiloxanes containing three [25][26][27][28] or four [29][30][31] silicon atoms.…”