Homogeneous Photocatalytic Reactions with Organometallic and Coordination Compounds-Perspectives for Sustainable Chemistry

• Published in: ChemSusChem 2012-02, Vol.5 (2), p.352-371
• Main Author: Hoffmann, Norbert
• Format: Article
• Language: English
• Subjects: Alkenes - chemistry; Catalysis; Electron Transport; green chemistry; Green Chemistry Technology - methods; homogeneous catalysis; organic synthesis; Organometallic Compounds - chemistry; Photochemical Processes; photochemistry; transition metals
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.201100286

Since the time of Giacomo Ciamician at the beginning of the 20th century, photochemical transformations have been recognized as contributing to sustainable chemistry. Electronic excitation significantly changes the reactivity of chemical compounds. Thus, the application of activation reagents is frequently avoided and transformations can be performed under mild conditions. Catalysis plays a central role in sustainable chemistry. Stoichiometric amounts of activation reagents are often avoided. This fact and the milder catalytic reaction conditions diminish the formation of byproducts. In the case of homogeneous catalysis, organometallic compounds are often applied. The combination of both techniques develops synergistic effects in the sense of “Green Chemistry”. Herein, metal carbonyl‐mediated reactions are reported. These transformations are of considerable interest for the synthesis of complex polyfunctionalized compounds. Copper(I)‐catalyzed [2+2] photocycloaddition gives access to a large variety of cyclobutane derivatives. Currently, a large number of publications deal with photochemical electron‐transfer‐induced reactions with organometallic and coordination compounds, particularly with ruthenium complexes. Several photochemically induced oxidations can easily be performed with air or molecular oxygen when they are catalyzed with organometallic complexes. Photochemical reaction conditions also play a certain role in CH activation with organometallic catalysts, for instance, with alkanes, although such transformations are conveniently performed with a variety of other photochemical reactions. Solar powered: Photochemical conditions significantly alter the outcome of chemical reactions. Consequently, the scope of catalytic transformations with organometallic and coordination compounds is also considerably enlarged. This article provides a short overview on such reactions and their application to organic synthesis. The review also indicates synergistic effects of photochemistry and catalysis with perspectives for a sustainable chemistry.