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.
Subject(s)
Alkenes/chemistry , Epoxy Compounds/chemical synthesis , Gallium/chemistry , Organometallic Compounds/chemistry , Catalysis , Epoxy Compounds/chemistry , Ligands , Models, Molecular , Molecular Structure , Organometallic Compounds/chemical synthesisABSTRACT
We demonstrate that a simple gallium(III) complex, [Ga(phen)(2)Cl(2)]Cl (phen = 1,10-phenanthroline), can serve as a homogeneous catalyst for the epoxidation of alkenes. The olefin epoxidations proceed relatively quickly at mild temperatures and, under optimum conditions, are highly selective for the epoxide product.
ABSTRACT
An electrostatically self-assembled film of PMo12/H6 has successfully been prepared on quartz substrates by alternating adsorption of [PMo12O40(3-) (PMo12) and a bipolar hemicyanine derivative of (E)-1,1'-(hexane-1,6-diyl)bis(4-(4-(dimethylamino)styryl)pyridinium) bromide (H6Br2). The UV-visible spectra showed that the film was uniformly deposited and the charge transfer between two film-forming components might occur in the film. The photocatalytic performance of the film was studied for the degradation of aqueous dye Methyl Red (MR) under UV irradiation. The degradation of MR follows Langmuir-Hinshelwood first-order kinetics.
