Transition-Metal-Substituted Keggin-Type Germanotungstates for Catalytic Conversion of Carbon Dioxide to Cyclic Carbonate

Abstract

The tetra-n-heptylammonium salts of transition-metal-substituted (TMS) Keggin type germanotungstates [(n-C 7 H 15 ) 4 N] n GeW 11 MO 39 (M = Mn 2? , Fe 3? , Co 2? , Ni 2? , Cu 2? and Zn 2? , n = 5 or 6) were found to be efficient catalysts for cyclic carbonates synthesis from epoxides and CO 2 under solvent-free and halogen-free condition. The catalytic activities were significantly influenced by the transition metal and the countercation and a plausible mechanism was proposed.

Mechanism of the Cycloaddition of Carbon Dioxide and Epoxides Catalyzed by Cobalt‐Substituted 12‐Tungstenphosphate

“…In contrast, high yields and selectivities were observed in the cycloaddition with Co‐substituted catalysts (Table 1, entries 3 and 4). Previous reports suggested Co substitution also increases the reactivity of solicotungstate6a and germanotungstate6b catalysts (Table 1, entries 5 and 6).…”

“…6a; reaction conditions: catalyst (0.286 μmol), PO (28.6 mmol), 3.5 MPa CO 2 , 150 °C, 2 h. [f] See ref. 6b; reaction conditions: catalyst (0.286 µmol), PO (28.6 mmol), 3 MPa, 150 °C, 2 h. TBA=( n ‐C 4 H 9 ) 4 N, THA=( n ‐C 7 H 15 ) 4 N.…”

Synthesis, crystal structure, mass spectrometry, electrochemistry and magnetism of a MnIII-substituted trilacunary Keggin tungstosilicate

“…4 Examples in catalysis include a tetranuclear Mn II 4 sandwich-type POM complex, Cs 10 [Mn 4 (H 2 O) 2 (α-PW 9 O 34 ) 2 ]•13H 2 O, that catalyzes aerobic epoxidation of styrene, cyclohexene, and cis-cyclooctene 5 and a Mn II -monosubstituted Keggin type germanotungstate, [(n-C 7 H 15 ) 4 N] 4 H 2 [GeW 11 MnO 39 ], that is an efficient catalyst for the synthesis of cyclic carbonates from epoxides and CO 2 under solvent-free and halogen-free conditions. 6 Other examples are a Mn II Mn III 3 tetrasubstituted sandwich-type phosphotungstate, K 7 [Mn 4 (H 2 O) 2 (α-B-PW 9 -O 34 ) 2 ], and a Mn III -monosubstituted Keggin type silicotungstate, K 5 [SiW 11 Mn III (H 2 O)O 39 ], that show high catalytic activity and selectivity in the oxygen delignification of kraft pulp. 7 For magnetochemical studies the advantage of POM systems is that the bulky diamagnetic POM ligand effectively isolates the encapsulated magnetic cluster and annihilates intermolecular magnetic exchange interactions.…”

Synthesis of Propylene Carbonate from Epoxide and CO2 Catalyzed by Carbon Nanotubes Supported Fe1.5PMo12O40

“…However, most of these heterogeneous systems require high pressures and high temperature. Taking into account the fact that several homogeneous based POMs catalysts have proven their performance in the cycloaddition of CO 2 [4,20], their exploration as heterogeneous catalyst systems is a promising way. It is well known that redox and acid-base properties of POMs can be adjusted by varying the heteroatom, counter anion, and addenda atoms.…”