Carbon dioxide activated complex

A. Behr, Carbon Dioxide Activation by Metal Complexes, VCH, Weinheim, 1988. 

In recent years there has been a growing interest in the chemistry of carbon dioxide, stimulated by current anxieties about alternative petrochemical feedstocks. One aspect under active exploration involves carbon dioxide activation via coordination to a transition metal, and indeed transition metal ions do form C02 complexes.177 The number of simple and reasonably stable complexes is still relatively small and usually limited to low oxidation state metal ions. There are many systems where C02 is used as a reagent giving rise to systems which, while not true C02 complexes, may simplistically be viewed as the products of insertion into metal-ligand bonds, e.g. reaction (9), where if L = H, formates are produced if L = OH, carbonates or bicarbonates result L = NR2 yields dialkylcarbamates and if L = R, carboxylate products result. Much of this area has recently been reviewed and will not be considered further.149... 

Reactions that combine C-H activation with a C-C bond-forming event are invaluable synthetic tools, allowing concise construction of carbon frameworks. Rhodium(i) catalysts have been shown to catalyze alkane carbonylation [21]. Recently, Sakakura and co-workers succeeded in subjecting methane to a catalytic acetaldehyde synthesis [22], They found that, in dense carbon dioxide, the complex [RhCl(PMe3)3] catalyzed the carbonylation of methane with 77 turnovers. 

The binding of carbon dioxide to a transition metal center, which can be brought about in various ways, generally involves activation of the molecule and several spectroscopic methods are suitable allowing the characterization of CO2 complexes [30]. In order to obtain a better understanding of carbon dioxide activation several CO2 complexes have been investigated and described but the formation of a transition metal-C02 complex is not a necessary prerequisite for catalytic processes converting CO2 into usable chemical products [1 b]. 

Monographs (a) A. Behr, Carbon Dioxide Activation by Metal Complexes, VCH Weinheim, 1988 (b) W. Keim (Ed.), Catalysis in Ci-Chemistry, D. Reidel, Dordrecht, 1983. 

Topics that have formed the subjects of reviews this year include contemporary issues in electron transport research, dynamics of bimolecular photoelectron transfer reactions, photophysical properties of functionalised fullerene derivatives, carbon-carbon bond formation via radical ions, photoinduced electron transfer processes in ketone, aldehyde, and ester synthesis, photochemical reactions between arenenitriles and benzylic donors, photo-oxidation of conjugated dienes, photoredox reactions of aromatic nitro compounds, electron transfer-mediated photochemistry of some unsaturated nitrogen-containing compounds, reactions of 02( Ag), carbon dioxide activation by aza-macrocyclic complexes, and photochromism of chalcone derivatives. ... 

Behr A (1988) Carbon dioxide activation by metal complexes, VCH.Weinheim, Germany... 

Kolomnikow, I. S. Lysyak, T.V. Carbon-Dioxide in Coordination Chemistry and Catalysis, Russ. Chem. Rev. 1990,59, 589. (f) Behr, A. Carbon Dioxide Activation by Metal Complexes, VCH, Weinheim, 1988. (g) Darensbourg, D. J. Kudaroski, R. A. The activation of carbon dioxide by metal complexes, Adv. Organomet. Chem. 1983, 22, 129. (h) Eisenberg, R. Hendricksen, D. E. The binding and activation of carbon monooxide, carbon dioxide, and nitric oxide and their homogeneously catalyzed reactions, Adv. Catal. 1979, 28, 79. (i) Souter, P. F. Andrews, L. P. F. A Spectroscopic and Theoretical-Study of the Reactions of Group-6 Metal Atoms with Carbon-Dioxide,/. Am. Chem. Soc. 1991,119, 7350. 

Carbonic anhydrase (CA) is a zinc metalloenzyme involved in mammalian respiration, which catalyzes the hydration of carbon dioxide. Copper-complexed TPPC, competitively inhibits CA enzymatic activity as does copper-complexed TPPSj [32]. Experiments comparing the spectrophotometric characteristics of the two porphyrins in the presence of CA and apo-CA indicate that the zinc atoms in the active site of the enzyme are indeed involved in the interaction between the porphyrins and the enzyme. The metal-free porphyrins TPPSj and TPPC, do not inhibit the enzymatic activity of CA. Further, the spectrophotometric characteristics of these porphyrins in the presence of apo-CA were identical to those in the presence of wild-type CA, indicating the lack of involvement of the active site-coordinated zinc in the porphyrin-enzyme interaction for metal-free porphyrins. 

Scheme 5.1. This scheme shows the formation of a carbon-bonded Ni(ll) complex by reaction of CO2 with [Ni(cyclam)]+. Reprinted from Scheme 3 J. Costamagna, G. Ferraudi, J. Canales and J. Vargas, Carbon dioxide activation by aza-macrocyclic complexes. Coordination Chemistry Reviews 148 (1996) 221-248. Copyright 1996, with permission of Elsevier.

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