Modulating the Elementary Steps of Methanol Carbonylation by Bridging the Primary and Secondary Coordination Spheres was written by Gregor, Lauren C.;Grajeda, Javier;Kita, Matthew R.;White, Peter S.;Vetter, Andrew J.;Miller, Alexander J. M.. And the article was included in Organometallics in 2016.Recommanded Product: 66943-05-3 This article mentions the following:
Kinetics and mechanism of methanol carbonylation catalyzed by iridium NCP-pincer 3-(diisopropylphosphinooxy)benzylamine complexes with N-pendant 15-crown-5 moiety was studied in dependence on secondary coordination of Lewis acidic centers. The rate of catalytic methanol carbonylation to acetic acid is typically limited by either the oxidative addition of Me iodide or the subsequent C-C bond-forming migratory insertion step. These elementary steps have been studied independently in acetonitrile solution for iridium aminophenylphosphinite (NCOP) complexes. The modular synthesis of NCOP ligands containing a macrocyclic aza-crown ether arm enables a direct comparison of two complementary catalyst optimization strategies: synthetic modification of the Ph backbone and noncovalent modification through cation-crown interactions with Lewis acids in the surrounding environment. The oxidative addition of Me iodide to iridium(I) carbonyl complexes proceeds readily at room temperature to form iridium(III) methylcarbonyl iodide complexes. The Me complexes undergo migratory insertion under 1 atm CO at 70° to produce iridium(III) acetyl species. Synthetic tuning, by incorporation of a methoxy group into the ligand backbone, had little influence on the rate. The addition of lithium and lanthanum salts, in contrast, enhanced the rate of C-C bond formation up to 25-fold. In the case of neutral iodide complexes, mechanistic studies suggest that Lewis acidic cations act as halide abstractors. In halide-free, cationic iridium complexes, the cations bind the macrocyclic ligand arm, further activating the iridium(III) center. The macrocyclic ligand is essential to the observed reactivity: complexes supported by acyclic diethylamine-containing ligands underwent migratory insertion slowly, Lewis acid effects were negligible, and the acetyl products decomposed over time. In the experiment, the researchers used many compounds, for example, 1,4,7,10-Tetraoxa-13-azacyclopentadecane (cas: 66943-05-3Recommanded Product: 66943-05-3).
1,4,7,10-Tetraoxa-13-azacyclopentadecane (cas: 66943-05-3) belongs to ethers. The oxygen atom in ethers are more electronegative than carbon, thus the hydrogens which are alpha to the ethers are more acidic than the simple hydrocarbons. Autoxidation is the spontaneous oxidation of a compound in air. In the presence of oxygen, ethers slowly autoxidize to form hydroperoxides and dialkyl peroxides. If concentrated or heated, these peroxides may explode. To prevent such explosions, ethers should be obtained in small quantities, kept in tightly sealed containers, and used promptly.Recommanded Product: 66943-05-3
Referemce:
Ether – Wikipedia,
Ether | (C2H5)2O – PubChem