Catalysis of Alkene Epoxidation by a Series of Gallium(III) Complexes with Neutral N-Donor Ligands

Abstract

Six gallium(III) complexes with N-donor ligands were synthesized to study the mechanism of Ga(III)-catalyzed olefin epoxidation. These include 2:1 ligand/metal complexes with the bidentate ligands ethylenediamine, 5-nitro-1,10-phenanthroline, and 5-amino-1,10-phenanthroline, as well as 1:1 ligand/metal complexes with the tetradentate N,N'-bis(2-pyridylmethyl)-1,2-ethanediamine, the potentially pentadentate N,N,N'-tris(2-pyridylmethyl)-1,2-ethanediamine, and the potentially hexadentate N,N,N',N'-tetrakis(2-pyridylmethyl)-1,2-ethanediamine. In solution, each of the three pyridylamine ligands appears to coordinate to the Ga(III) through four donor atoms. The six complexes were tested for their ability to catalyze the epoxidation of alkenes by peracetic acid. Although the complexes with relatively electron-poor phenanthroline derivatives display faster initial reactivity, the gallium(III) complexes with the polydentate pyridylamine ligands appear to be more robust, with less noticeable decreases in their catalytic activity over time. The more highly chelating trispicen and tpen are associated with markedly decreased activity.

Gallium and Indium Compounds in Homogeneous Catalysis

“…The use of phenanthroline (phen) ligands led to the highest catalytic activities with the selective formation of the epoxide product. 45, 46 Penta-and hexadentate polyamine ligands exhibited the lowest activity, suggesting the competition between the N-ligand and the coordination of PAA R . Such trends were rationalized by means of DFT calculations.…”

“…The one-pot reaction of carboxylic acids with alcohols in the presence of InBr 3 (5 mol%) and excess polymethylhydrosiloxane (PMHS) afforded the corresponding ether derivatives (46). 75 Such an In(III)-catalyzed reduction reaction proceeds via the initial formation of the ester derivatives and a subsequent reduction by PHMS to form the ether product along with reticulated polymethylsiloxane.…”

A Highly Efficient Heterogeneous Catalyst of Bimetal-Organic Frameworks for the Epoxidation of Olefin with H2O2

“…The catalytic epoxidation of alkenes play an important role in the organic synthetic chemistry and industrial production, since epoxy compounds are also widely used in synthetic resins, adhesives, coatings, and pharmaceutical synthesis. Homogeneous catalysis with metal complexes is generally highly active for the oxidation of a wide range of olefins [1][2][3]. Recently, iminium salt [4] and ammonium salt [5] were reported as metal-free catalysts for enantioselective asymmetric epoxidation of olefins.…”

Oxidation of olefins with H2O2 catalyzed by gallium(III) nitrate and aluminum(III) nitrate in solution

“…The interaction of hydrogen peroxide with soluble derivatives of aluminum, gal-lium and some other non-transition metals leads to the formation of hydroxyl radicals which induce the oxidation of alkanes [13,[15][16][17][18][19][20]. Goldsmith and co-workers described epoxidation of olefins with peroxyacetic acid catalyzed by gallium complexes with N-donor ligands [21][22][23]. It is noteworthy that H 2 O 2 was not effective in that reaction.…”