Selective and Additive-Free Hydrogenation of Nitroarenes Mediated by a DMSO-Tagged Molecular Cobalt Corrole Catalyst

Silver Anniversary of the Renaissance in Metallocorrole Chemistry

The 1999 discovery of one-pot corrole synthesis opened the floodgates for research on these unique macrocyclic chelating agents. The enormous impact of this discovery has been documented in numerous reviews describing advances in the synthetic chemistry of corroles and selected applications in which corroles are key components. Our silver anniversary review focuses on the structures and reactions of all well characterized corrole-chelated d- and p-block metal complexes, including discussions of their electronic excited-state physics and chemistry. Emphasis is placed on electronic structure of the trinegative N4 coordination core, which stabilizes high-valent metals and activates low-valent ones, and, importantly, profoundly influences ground- and excited-state reactivity. Our story highlights the unique properties of corroles that have made them the molecular components of choice in a plethora of applications. These include their utility for sensing gases and anions, rescue of vital biomolecules from oxidative damage, destruction of cancerous cells, and catalysis of reactions critical for organic synthesis, as well as those involved in clean energy processes such as production of hydrogen and reduction of oxygen. In our view, research on corroles will continue to grow by leaps and bounds, most especially in areas of human health research and renewable energy science and technology.

Catalytic Application of Biochar Functionalized Copper-l-histidine for the Chemo and Homoselective Conversion of Cyanides to Amides and Reduction of Nitroarenes to anilines

In our study, we aimed to use olive pomace, food industry waste, as biomass to produce biochar nanoparticles. The surface of the biochar was functionalized with the l-histidine ligand, and then cupric acetate was added to prepare Cu-l-histidine@biochar as a final catalyst for the chemo- and homoselective synthesis of amide and aniline derivatives. To characterize the novel catalyst, we employed various techniques. Another notable feature of this catalyst is its reusability, which maintained significant efficiency even after multiple uses in reactions.

Synergy of redox-activity and hemilability in thioamidato cobalt(III) complexes for the chemoselective reduction of nitroarenes to anilines: catalytic and mechanistic investigation

Reduction of nitro-compounds to amines is one of the most often employed and challenging catalytic processes in the fine and bulk chemical industry. Herein, we present two series of mononuclear homoleptic and heteroleptic Co(III) complexes, i.e., [Co(LNS)3] and [Co(LNS)2L1L2]x+, respectively (x = 0 or 1, LNS = pyrimidine- or pyridine-thioamidato, L1/L2 = thioamidato, phosphine or pyridine), which successfully catalyze the transformation of nitroarenes to anilines by methylhydrazine. The catalytic reaction can be accomplished for a range of electronically and sterically diverse nitroarenes, using mild experimental conditions and low catalyst loadings, resulting in the corresponding anilines in high yields, with high chemoselectivity, and no side-products. Electronic and steric properties of the ligands play pivotal role in the catalytic efficacy of the respective complexes. In particular, complexes bearing ligands of high hemilability/lability and being capable of stabilizing lower metal oxidation-states exhibit the highest catalytic activity. Mechanistic investigations suggest the participation of the Co(III) complexes in two parallel reaction pathways: (a) coordination-induced activation of methylhydrazine and (b) reduction of nitroarenes to anilines by methylhydrazine, through the formation of Co(I) and Co-hydride intermediates.

Reaction of Corroles with Sarcosine and Paraformaldehyde: A New Facet of Corrole Chemistry

Details on the unexpected formation of two new (dimethylamino)methyl corrole isomers from the reaction of 5,10,15-tris(pentafluorophenyl)corrolatogallium(III) with sarcosine and paraformaldehyde are presented. Semi-empirical calculations on possible mechanism pathways seem to indicate that the new compounds are probably formed through a Mannich-type reaction. The extension of the protocol to the free-base 5,10,15-tris(pentafluorophenyl)corrole afforded an unexpected new seven-membered ring corrole derivative, confirming the peculiar behavior of corroles towards known reactions when compared to the well-behaved porphyrin counterparts.

Mild and Efficient Heterogeneous Hydrogenation of Nitroarenes Facilitated by a Pyrolytically Activated Dinuclear Ni(II)-Ce(III) Diimine Complex

We communicate the assembly of a solid, Ce-promoted Ni-based composite that was applied as catalyst for the hydrogenation of nitroarenes to afford the corresponding organic amines. The catalytically active material described herein was obtained through pyrolysis of a SiO₂-pellet-supported bimetallic Ni-Ce complex that was readily synthesized prior to use from a MeO-functionalized salen congener, Ni(OAc)₂·4 H₂O, and Ce(NO₃)₃·6 H₂O. Rewardingly, the requisite ligand for the pertinent solution phase precursor was accessible upon straightforward and time-saving imine condensation of ortho-vanillin with 1,3-diamino-2,2′-dimethylpropane. The introduced catalytic protocol is operationally simple in that the whole reaction set-up is quickly put together on the bench without the need of cumbersome handling in a glovebox or related containment systems. Moreover, the advantageous geometry and compact-sized nature of the used pellets renders the catalyst separation and recycling exceptionally easy.

Generation of Cobalt-Containing Nanoparticles on Carbon via Pyrolysis of a Cobalt Corrole and Its Application in the Hydrogenation of Nitroarenes

We report on the manufacture of a state-of-the-art heterogeneous non-noble metal catalyst, which is based on a molecularly well-defined phosphine-tagged cobalt corrole complex. This precursor compound is readily synthesized from convenient starting materials while the active material is obtained through wet-impregnation of the pertinent metalliferous macrocycle onto carbon black followed by controlled pyrolysis of the loaded carrier material under an inert gas atmosphere. Thus, the obtained composite was then applied in the heterogeneous hydrogenation of various nitroarenes to yield a vast array of valuable aniline derivatives that were conveniently isolated as their hydrochloride salts. The introduced catalytic protocol is robust and user-friendly with the entire assembly of the reaction set-up enabling the conduction of the experiments on the laboratory bench without any protection from air.