- [Show abstract] [Hide abstract] ABSTRACT: Nickel nanoparticles (NPs) supported on different undoped or doped with N or B graphenes (Gs) have been tested as catalyst for the hydrosilylation of aldehydes to obtain the corresponding siloxanes with high conversion and good selectivity in short reaction time. The different Gs employed were obtained by pyrolysis under inert atmosphere of alginate or chitosan, modified or not with boric acid. Then the metal NPs obtained by polyol reduction method using ethylene glycol were adsorbed on Gs. The Ni-containing G catalysts were characterized by electron microscopy, XPS and Raman spectroscopy. The scope of the Ni/G catalyst includes aliphatic and aromatic aldehydes as well as a variety of hydrosilanes.
- [Show abstract] [Hide abstract] ABSTRACT: Metal oxide nanoparticles supported on graphene exhibit high catalytic activity for oxidation, reduction and coupling reactions. Here we show that pyrolysis at 900 °C under inert atmosphere of copper(II) nitrate embedded in chitosan films affords 1.1.1 facet-oriented copper nanoplatelets supported on few-layered graphene. Oriented (1.1.1) copper nanoplatelets on graphene undergo spontaneous oxidation to render oriented (2.0.0) copper(I) oxide nanoplatelets on few-layered graphene. These films containing oriented copper(I) oxide exhibit as catalyst turnover numbers that can be three orders of magnitude higher for the Ullmann-type coupling, dehydrogenative coupling of dimethylphenylsilane with n-butanol and C-N cross-coupling than those of analogous unoriented graphene-supported copper(I) oxide nanoplatelets.
- [Show abstract] [Hide abstract] ABSTRACT: Graphene oxide promotes the oxidative degradation of α-guaiacylglycerol-β-guaiacyl ether, a lignin model compound, in different solvents including acetonitrile, toluene and water mainly to guaiacol, 2-methoxyquinone, vanillic acid and coniferyl aldehyde. Reduced graphene oxide and B-doped graphene exhibit similar activity as graphene oxide. Control experiments indicate that metal impurities should play a marginal role in the observed catalytic activity.
- [Show abstract] [Hide abstract] ABSTRACT: An ew and efficient nickel-basedp rotocol for the N-arylation of indolesa nd carbazoles with aromatic chlorides, the least expensive of the aryl halides,i sd escribed. Thep rocedure provides selectively N-(hetero)arylation products in good to high yields,i ns hortr eaction times andw ithout adding an excess of ligands.
- [Show abstract] [Hide abstract] ABSTRACT: The inside cover picture, provided by T. R. Belderrain, M. C. Nicasio and co-workers, illustrates the first example of nickel-mediated N-(hetero)arylation of indoles and carbazoles with (hetero)aromatic chlorides, the least expensive of aryl halides. The reported procedure, based on the use of the Ni(0) complex [(IPr)Ni(styrene)2] as catalytic precursor, affords the products in good to high yields, in short reac tion times without the addition of an excess of the N-heterocycle carbene ligand. Details can be found in the communication on pages 907–911 (S. G. Rull, J. F. Blandez, M. R. Fructos, T. R. Belderrain, M. C. Nicasio, Adv. Synth. Catal. 2015, 357, 907–911; DOI: 10.1002/adsc.201500030).
- [Show abstract] [Hide abstract] ABSTRACT: Palladium nanoparticles (Pd NPs) have been supported on undopped and N- or B-doped graphenes (Gs) and these materials have been used as catalysts for the dehydrogenative coupling of hydrosilanes and amines to form silazanes. Working under optimal conditions, a conversion over 99 % and selectivity of 84 % were achieved for the reaction of dimethylphenylsilane with morpholine. In contrast, copper (Cu NPs) or nickel nanoparticles (Ni NPs) supported on G did not promote the formation of the corresponding Si-N coupling product. It was found that Pd/G performed better for this coupling than analogous catalysts in where Pd NPs were supported in active carbon, multiwall carbon nanotubes or diamond NPs. Pd/G as catalyst has a wide substrate scope, including aliphatic and aromatic amines and mono or dihydrosilanes. Pd/G undergoes a gradual deactivation due to the growth and partial agglomeration of Pd NPs and aggregation of the G sheets, as observed by TEM.
- [Show abstract] [Hide abstract] ABSTRACT: Copper nanoparticles (NPs) supported on a series of undoped and doped graphene materials (Gs) have been obtained by pyrolysis of alginate or chitosan biopolymers, modified or not with boric acid, containing Cu2+ ions at 900 °C under inert atmosphere. The resulting Cu-G materials containing about 17 wt % Cu NPs (from 10 to 200 nm) exhibit high catalytic activity for the dehydrogenative coupling of silanes with alcohols. The optimal material consisting on Cu-(B)G is more efficient than Cu NPs on other carbon supports.
- [Show abstract] [Hide abstract] ABSTRACT: A novel bis-styrene IPrNi0 derivative has been synthesized from the reaction of Ni(COD)2 and free 1,3-bis(2,6-diisopropylphenyl)imidazolidene (IPr) ligand in the presence of styrene. The complex has been characterized by spectroscopic data as well as by X-ray crystallography. Its catalytic performance in the amination reaction of aryl tosylates is also reported. The catalytic reactions proceed in a very selective manner, affording moderate to high yields of cross-coupling products in short reaction times at 110 °C.
Universitat Politècnica de València
Valenza, Valencia, Spain
- Department of Chemistry
Universidad de Huelva
Huelva, Andalusia, Spain
- Center for Research in Sustainable Chemistry (CIQSO)
Universidad de Sevilla
Hispalis, Andalusia, Spain
- Inorganic Chemistry