88108-59-2Relevant articles and documents
Structural and Electronic Noninnocence of α-Diimine Ligands on Niobium for Reductive C-Cl Bond Activation and Catalytic Radical Addition Reactions
Nishiyama, Haruka,Ikeda, Hideaki,Saito, Teruhiko,Kriegel, Benjamin,Tsurugi, Hayato,Arnold, John,Mashima, Kazushi
supporting information, p. 6494 - 6505 (2017/09/12)
A d0 niobium(V) complex, NbCl3(α-diimine) (1a), supported by a dianionic redox-active N,N′-bis(2,6-diisopropylphenyl)-1,4-diaza-2,3-dimethyl-1,3-butadiene (α-diimine) ligand (ene-diamido ligand) served as a catalyst for radical addition reactions of CCl4 to α-olefins and cyclic alkenes, selectively affording 1:1 radical addition products in a regioselective manner. During the catalytic reaction, the α-diimine ligand smoothly released and stored an electron to control the oxidation state of the niobium center by changing between an η4-(σ2,π) coordination mode with a folded MN2C2 metallacycle and a κ2-(N,N′) coordination mode with a planar MN2C2 metallacycle. Kinetic studies of the catalytic reaction elucidated the reaction order in the catalytic cycle: the radical addition reaction rate obeyed first-order kinetics that were dependent on the concentrations of the catalyst, styrene, and CCl4, while a saturation effect was observed at a high CCl4 concentration. In the presence of excess amounts of styrene, styrene coordinated in an η2-olefinic manner to the niobium center to decrease the reaction rate. No observation of oligomers or polymers of styrene and high stereoselectivity for the radical addition reaction of CCl4 to cyclopentene suggested that the C-C bond formation proceeded inside the coordination sphere of niobium, which was in good accordance with the negative entropy value of the radical addition reaction. Furthermore, reaction of 1a with (bromomethyl)cyclopropane confirmed that both the C-Br bond activation and formation proceeded on the α-diimine-coordinated niobium center during transformation of the cyclopropylmethyl radical to a homoallyl radical. With regard to the reaction mechanism, we detected and isolated NbCl4(α-diimine) (6a) as a transient one-electron oxidized species of 1a during reductive cleavage of the C-X bonds; in addition, the monoanionic α-diimine ligand of 6a adopted a monoanionic canonical form with selective one-electron oxidation of the dianionic ene-diamido form of the ligand in 1a.
Dinuclear molybdenum cluster-catalyzed radical addition and polymerization reactions by tuning the redox potential of a quadruple bonded Mo2 core
Tsurugi, Hayato,Yamada, Kohei,Majumdar, Moumita,Sugino, Yoshitaka,Hayakawa, Akio,Mashima, Kazushi
supporting information; experimental part, p. 9358 - 9361 (2011/11/05)
We developed dinuclear molybdenum cluster-catalyzed radical addition and polymerization reactions by tuning the redox potential of the Mo2 core. A 2,4,6-triisopropylbenzoate-supported Mo2 complex acts as a catalyst for radical addition reactions of polyhaloalkanes to 1-alkenes and cyclopentene, while amidinate- and guanidinate-supported Mo2 clusters are effective catalysts for the radical polymerization reaction of methyl methacrylate.
Adsorption and catalytic conversion of hydrocarbons on nanosized gold particles immobilized on alumina
Smirnov,Lanin,Vasil'kov,Nikolaev,Murav'eva,Tyurina,Vlasenko
, p. 2286 - 2289 (2007/10/03)
Gold and nickel particles immobilized on alumina were prepared by the metal vapor synthesis and anionic adsorption methods. The dispersion of metals was determined by X-ray diffraction and transmission electron microscopy. The activity of nanoparticles, tested in model catalytic reactions of CCl 4 addition to multiple bonds and allyl isomerization of allylbenzene, changes in a wide range (from 1 to 3000 (mole of product) (mole of Au) -1 h-1) and is parallel to the chromatographically measured heats of adsorption of the corresponding unsaturated substrates. The heat of adsorption of unsaturated hydrocarbons can serve as a criterion for the efficiency of the gold-containing catalyst in olefin conversion.
