Carbon dioxide complexes with transition metals

Pandey KK (1995) Reactivities of carbonyl sulfide (COS), carbon disulfide (CS2) and carbon dioxide (CO2) with transition metal complexes. Coord Chem Rev 140 37-114... 

Infrared spectral identification of adduct formation involving carbon dioxide and a transition metal complex has often been in error because of subsequent reactions of C02 with concomitant production of carbonato-, hydrogen-carbonato-, or carboxylato-metal complexes. Indeed Mason and Ibers (9) have suggested that the only acceptable structural characterization forjudging the authenticity of a class of transition metal-C02 complexes should be diffraction methods. X-ray structural studies have verified at least six C02 adducts which display all three types of bonding modes of... 

Carbon dioxide, 4 an important green house gas,45 is obtained in combustion of carbon and hydrocarbons, calcination of CaC03, and so on. It forms complexes with transition metals (Section 7-14) and inserts into MH and other bonds (Section 21-3). The gas is very soluble in ethanolamines, which are used to scrub C02 from gas streams. Liquid C02 at pressures up to 400 bar is a solvent for some organic compounds and is used to extract caffeine from coffee beans many studies of other applications of supercritical C02 have been conducted.46... 

Carbon dioxide is obtained by combustion of carbon in the presence of an excess of oxygen or by treating carbonates with dilute acids. Its important properties should already be familiar. It undergoes a number of insertion reactions (Section 24-A-3) similar to those of CS2 noted below, and a few complexes with transition metals are known. 

The interaction of carbon dioxide with transition metal complexes. I. S. Kolomnikov and M. K. Grigoryan, Russ. Chem. Rev. (Engl. Transl.), 1978,47, 334-353 (306). 

The chemistry of carbon dioxide with transition metal complexes is a field of research that has only recently received wide attention. One goal of research in this area is the development of efficient catalytic processes in which carbon dioxide is reduced by molecular hydrogen and/or incorporated into an organic molecule. Some examples of such desirable transformations... 

The carbon dioxide molecule exhibits several functionalities through which it may interact with transition metal complexes and/or substrates. The dominant characteristic of C02 is the Lewis acidity of the central carbon atom, and the principle mode of reaction of C02 in its main group chemistry is as an electrophile at the carbon center. Consequently, metal complex formation may be anticipated with basic, electron-rich, low-valent metal centers. An analogous interaction is found in the reaction of the Lewis acid BF3 with the low-valent metal complex IrCl(CO)(PPh3)2 (114). These species form a 1 1 adduct in solution evidence for an Ir-BF3 donor-acceptor bond includes a change in the carbonyl stretching frequency from 1968 to 2067 cm-1. 

Despite the fact that carbon dioxide (C02) is used in a great number of industrial applications, it remains a molecule of low reactivity, and methods have still to be identified for its activation. Both thermodynamic and kinetic problems are connected with the reactivity of C02, and few reactions are thermodynamically feasible. A very promising approach to activation is offered by its coordination to transition metal complexes, as both stoichiometric reactions of C-C bond formation and catalytic reactions of C02 are promoted by transition metal systems. Efforts to enhance the yield of hydrogen in water gas-shift (WGS) reactions have also been centered on C02 interactions with transition metal catalysts. The coordination on metal centers lowers the activation energy required in further reactions with suitable reactants involving C02, making it possible to convert this inert molecule into useful products. 

Less attention has been paid, however, to C02 organometallic chemistry during the past decade. Whilst many reduction or coupling reactions are known to proceed in the presence of stoichiometric or catalytic amounts of transition metal complexes, very few examples remain where the formation of a metal-C02 complex has led to an effective, catalytic reduction reaction of C02. Carbon dioxide complex photoactivation also represents an attractive route to CO bond cleavage, coupled with O-atom transfer. However, progress in the area of C02 utilization requires a better understanding of the reaction mechanisms, of the thermodynamics of reaction intermediates, and of structure-reactivity relationships. 

The first step in the activation of carbon dioxide by transition metal compounds is the formation of a M-C02 complex, since it is through coordination that the electronic structure of this molecule, and hence its reactivity, can be substantially modified. Transition metal complexes containing carbon dioxide in its intact form have received considable attention in the last decade (Inone et al, 1982), mainly with the aim of finding model systems for the activation of C02 and subsequent transformation into organic chemicals of comercial interest (Aresta et al, 1987). Despite considerable and intensive work in this area, the number of structurally characterized carbon dioxide complexes is stilt very limited, and they have been found to contain side-on (Alvarez et al, 1986), 72 -coordinated and, l2 C-coordinated (Calabrese et al, 1983) C02. 

A new stall in CO cheniistry was found when a few rcscardi groups investigated the reactions of carbon dioxide with transition metal coniplexes. The results, which have been published up to 1981, are summarized in this review. Some of the older reviews which have been published concern 1he reactions of CO with transition metal complexes 1-81 and the syntlietic reactions and chemical utilization of carbon dioxide [9-18]. 

If the peroxocarbonate complexes are prepared by reaction of dioxygen complexes of transition metals LnM(02)Xm (M = Pd, Pt, Rh, Ir) with carbon dioxide, [la] in principle, two ways are possible, that imply the formal insertion of carbon dioxide into the 0-0 (route 1, Scheme 1) or M-O (route 2, Scheme 1) bond. 

F. Power, T. Kozik, M. Interaction of Carbon Dioxide with Transition-Metal-Substituted Heteropolyanions in Nonpolar Solvents. Spectroscopic Evidence for Complex Formation, Inorg. Chem. 1998, 37, 4344. 

Carbon dioxide is abundant and readily available, but its reaction with transition metal complexes has not been extensively studied. A few examples of carbon dioxide insertion are known. Thus, formic acid can be formed by the insertion of carbon dioxide into the cobalt hydride bond U9>,2°). 

The effect of NH3 adsorption on catalytic activity and selectivity of cation-exchanged Y zeolite and natural clinoptilolite (deposit of Georgia) in ethanol transformation was investigated. The ODH of alcohol is accompanied by dehydration to ethylene and diethylether and deep oxidation to CO2 NH3 blocks the acidic active centers of dehydration of Y zeolites and promotes the oxidative activity of samples with transition metal cations. The influence of the ion nature for the catalytic transformation of ethanol was shown by a considerable increase of carbon dioxide formation after NH3 adsorption. The cation associated has been destroyed under NH3 influence, and NH3 formed with cations coordinated-unsaturated complexes. 

Magdesieva, T.V., T. Yamamoto, D.A. Tryk, and A. Fujishima (2002). Electrochemical reduction of CO2 with transition metal phthalocyanine and porphyrin complexes supported on activated carbon fibers. J. Electrochem. Soc. 149(6), D89-D95. Atoguchi, T., A. Aramata, A. Kazusaka, and M. Enyo (1991). Cobalt (II)-tetraphenylporphyrin-pyridine complex fixed on a glassy carbon electrode and its prominent catalytic activity for reduction of carbon dioxide. J. Chem. Soc. Chem. Commun. 13, 156-157. 

Borowiak MA, Jamroz MH, Dobrowolski JC, Bajdor K, Kazimirski JK, Mascetti J, Quaranta E, Tommasi I, Aresta M (2001) Application of the impulse oscillation model for modeling the formation of peroxocarbonates via carbon dioxide reaction with dioxygen transition metal complexes. A comparison with the experimental results obtained for Rh (q -02)ClP3 [P = phosphane ligand]. J Mol Catal A 165 45-54... 

Reactions of Carbon Dioxide.— The interaction of carbon dioxide with transition-metal complexes has been reviewed. Reaction of cmrbon dioxide with [TiCNMea) and 1,2-epoxycyclohexane followed by hydrolysis gives 2-hydroxy-... 

Trialkylborane additives promote the reduction of carbon dioxide to formate, via bis(diphosphine) Ni(II) and Rh(III) hydride complexes. Late transition metal hydrides, which can be formed by the reaction with molecular H2, transfer hydride to CO2 to yield a formate-borane adduct. In order to drive this process, the borane must be of appropriate Lewis acidity hence, weaker... 

This chapter is concerned entirely with the insertion of carbon monoxide into transition metal-carbon cr-bonds. Sulfur dioxide insertion 154, 239), also common among transition metal-carbon complexes, will be treated in a complementary review, which is to appear later. Subject to the restrictions given at the beginning of Section VI, an attempt has been made at a complete literature coverage of the insertion of CO. Particular emphasis focuses on recent results, especially those of a kinetic and stereochemical nature. 

Reactions of carbon subsulphide and of elementary phosphorus, sulphur and selenium with complexes of the platinum metals Sulphur dioxide insertion reactions of transition metal alkyls and related complexes... 

Palladium(II) complexes possessing bidentate ligands are known to efficiently catalyze the copolymerization of olefins with carbon monoxide to form polyketones.594-596 Sulfur dioxide is an attractive monomer for catalytic copolymerizations with olefins since S02, like CO, is known to undergo facile insertion reactions into a variety of transition metal-alkyl bonds. Indeed, Drent has patented alternating copolymerization of ethylene with S02 using various palladium(II) complexes.597 In 1998, Sen and coworkers also reported that [(dppp)PdMe(NCMe)]BF4 was an effective catalyst for the copolymerization of S02 with ethylene, propylene, and cyclopentene.598 There is a report of the insertion reactions of S02 into PdII-methyl bonds and the attempted spectroscopic detection of the copolymerization of ethylene and S02.599... 

Equations 1 to 3 show some of fixation reactions of carbon dioxide. Equations la and lb present coupling reactions of CO2 with diene, triene, and alkyne affording lactone and similar molecules [2], in a process catalyzed by low valent transition metal compounds such as nickel(O) and palladium(O) complexes. Another interesting CO2 fixation reaction is copolymerization of CO2 and epoxide yielding polycarbonate (equation 2). This reaction is catalyzed by aluminum porphyrin and zinc diphenoxide [3],... 

Abstract This chapter focuses on well-defined metal complexes that serve as homogeneous catalysts for the production of polycarbonates from epoxides or oxetanes and carbon dioxide. Emphasis is placed on the use of salen metal complexes, mainly derived from the transition metals chromium and cobalt, in the presence of onium salts as catalysts for the coupling of carbon dioxide with these cyclic ethers. Special considerations are given to the mechanistic pathways involved in these processes for the production of these important polymeric materials. 

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