| Abstract |
This work concerns recent advances (since 2014) in the chemistry of C-homoscorpionate tris( pyrazol-1 yl) methanes and in the use of their transition metal complexes as versatile catalysts for challenging and industrially significant reactions. Thus, oxidative functionalization of alkanes, alkenes and alcohols, reduction of carbon dioxide, as well as C-C and C-N couplings, are addressed. The reactions include i) the selective oxidation of alkanes (typically cyclohexane as a model substrate) with ozone (directly to carboxylic acids) or hydrogen peroxide (into alkyl hydroperoxides, alcohols, and ketones), ii) the hydrocarboxylation of C-n alkanes (with carbon monoxide and water) into the corresponding Cn+1 carboxylic acids, and iii) the carbon dioxide hydrogenation to methanol, catalyzed by sufficiently active, selective and sustainable (homogeneous or supported) catalytic systems based on tris(pyrazol-1-yl)methane metal complexes. Attention is also paid to the homogeneous catalytic performance of C-scorpionate metal-complexes for the Heck, Sonogashira and Henry C-C couplings and to the azide-alkyne Huisgen cycloaddition. Unconventional systems and conditions of sustainable significance, including the use of ionic liquids or supercritical fluids as reaction media, and of microwave irradiation (as alternative energy source), are highlighted, and the preferable requirements for a prospective homogeneous or supported catalyst in the transformations of the above substrates are identified. (C) 2019 Elsevier B.V. All rights reserved. |
