Transition metal reaction with carbon dioxide

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],... 

A recent report 121) on the reactions of tetrakis(trimethylphosphine) iron, Fe(PMe3)4, with carbon dioxide reveals a rich and varied chemistry, illustrating many of the reaction modes of C02 with low-valent transition metal complexes. Two primary reactions of C02 with Fe(PMe3)4 are noted, as a consequence of the two isomers in equilibrium (49). 

Insertion reactions with carbon monoxide or sulfur dioxide are well known for compounds with carbon-transition-metal bonds, e.g.,... 

The reactions of propargylamines with carbon dioxide have been systematically examined in the presence of transition metals Pd(OAc)2 was the best catalyst for the formation of the corresponding oxazolidinone 212 <02JOC16>. 

Reactions of carbon dioxide with transition metal compounds, including the alkyls and aryls, have been recently reviewed (130a). 

The reactions of organometallic 20 compounds of transition metals (29) with molecular nitrogen and carbon dioxide... 

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]. 

In the field of olefin carboxylation, stoichiometric reactions have been described to occur between non-activated alkenes, CO2 and an electron-rich transition-metal complexes, such as Ni(0) [3], Ti(II) [4] or Fe(0) [5]. A Pd-catalyzed CO2 fixation occurs into methylenecyclopropane derivatives affording lactones [6]. The reaction of carbon dioxide with ethylene is difficult and its carboxylation to propionic acid, catalyzed by Rh derivatives [7], needs drastic experimental conditions. 

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. 

Reactions of Carbon Dioxide with Carbon-Carbon Bond Formation Catalyzed by Transition Metal Complexes"... 

However, till now catalytic reactions of ethene and carbon dioxide are not known. But the great number of successful stoichiometric reactions between these two molecules makes it probable to achieve the catalytical bond formation in the near future. A short survey about the various reactions of ethene and other alkenes with carbon dioxide is given in the following sections in the order of transition metals applied. 

Nickel is a further transition metal of high importance in CO2 activation. Ethene and carbon dioxide react in the presence of nickel-(1,5,9-cyclododecatriene) and a chelating ligand such as dcpe or 2,2 bipyridyl (bipy) yielding an oxanickelacyclopentanone which can be decomposed to propionic acid, methyl propionate or - via succeeding reaction with carbon monoxide - to succinic anhydride [4,5]. Another catalyst leads to the formation of products with an ethene/ C02-ratio of 2 1 (Figure 4). By using nickelbis(cyclooctadiene) and... 

Though this review focus on homogeneous catalyzed reactions between unsatured hydrocarbons and carbon dioxide, also some related reactions without transition metal catalysts will be considered. It appears suitable to compare the different possibilities of catalytic and non-catalytic methods in the field of C-C linkage. For instance ionic reactions are well known routes to attach CO2 on a hydrocarbon chain. Living oligomers of ethene obtained with n-BuLi complexed by tertiary amines react with carbon dioxide and yield long-chain car xylic acids [27] (Equation 3). 

As in the monoene chapter, the stoichiometric and catalytic reactions of dienes with carbon dioxide will be discussed in the sequence of the transition metal applied. It is remarkable, that almost the same metals are described both in monoene and in diene/C02 chemistry. Two differences, however, should be stressed In the presence of molybdenum and tungsten complexes no interactions between dienes and carbon dioxide are reported (until now). On the other hand, palladium is a much more versatile and effective metal in diene/C02 than in monoene/CO chemistry. 

It is well known that oxiranes react with carbon dioxides yielding organic carbonates. Several transition metal catalysts permit very mild conditions and give high yields and selectivities in this reaction [63-65], but palladium catalysts proved to be particularly effective [66]. The question arose which reaction occurs when both butadiene and an oxirane are possible reaction partners of CO2. 

Comparable to the dienes (see Figure 14) also alkynes may react with carbon dioxide yielding both chain or cyclic products. As shown in Figure 30 a 1 1 reaction should result alkynoic acids or substituted pyrones. As a further possibility Figure 30 shows the hypothetical combination of acetylene and two moles of carbon dioxide giving alky-nedioic acids or pyronic acids. Once again the reactions will be considered according to the transition metal applied. 

The combination of hard oxophilic early transition metals and soft nucleophilic late transition metals with opposite functionalities, provided they do not inhibit one another, is a priori ideal for promoting cooperative effect. A proof of concept can be found in the stoichiometric reactivity of early—late heterobimetallic complexes featuring a metal-metal bond [76]. It has been shown that such complexes are good candidates to realize the heterolytic cleavage of a bond in polar and apolar substrates. An illustrative example by Bergman et al. is the reaction of the Zr-lr complex 20 with carbon dioxide which leads to the rupture of the metal—metal bond (Scheme 18) [77]. The CO2 insertion occurs in the expected fashion with the CO2 bridging the two metals, the carbon atom coordinated to iridium, and the oxygen atom on the zirconium center. 

Koyanagi GK, Bohme DK (2006) Gas-phase reactions of carbon dioxide with atomic transition-metal and main-group cations room-temperature kinetics and periodicities in reactivity. J Phys Chem A 110 1232-1241... 

Hydrides can be categorized in various classes according to the nature of the bond that links the metal and hydrogen. The following categories can usually be found in the literature ionic hydrides (hydrides with group 1 and 2 elements), covalent hydrides, polymeric hydrides, metallic hydrides, borderline hydrides, and transitirai metal complex hydrides. Here the reaction of ionic hydrides with carbon dioxide (CO2) is considered. Transition metal hydrides with the formula L M-H are discussed in Chap. 4, where the interaction of CO2 with analogous E-X systems (where E and X are different elements) is discussed. 

Braunstein P, Matt D, Nobel D (1988) Reactions of carbon dioxide with carbon-carbon bond formation catalyzed by transition metal complexes. Chem Rev 88 747-764... 

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-... 

The use of carbon dioxide in the synthesis of functional molecules is of considerable interest. An example is the industrially important reaction of epoxides with carbon dioxide to give cyclic carbonates. Also, functionalization of acetylenes and dienes with carbon dioxide on transition metal catalysts gives rise to the formation of cyclic lactones or dicarboxylic acids. The activation of carbon dioxide by metal complexes was reviewed in 1983 . Reactions of carbon dioxide with carbon-carbon bond formation catalyzed by transition metal complexes was reviewed in 1988 ", heterogenous catalytic reactions of carbon dioxide were reviewed in 1995, and the use of carbon dioxide as comonomers for functional polymers was reviewed in 2005. ... 

Carbon Dioxide.—The sole example of carbon dioxide insertion into a transition-metal-carbon bond is afforded by the reaction of Ti(A -C6H5)a-Pha with carbon dioxide, which produces (16). The suggested mechanism is... 

In this chapter, we discuss theoretical studies of some selected transition metal-catalyzed reactions of carbon dioxide to illustrate how important concepts and insights can be derived as a result of these studies. These selected reactions include hydrogenation of CO2 with Hj, coupling reactions of COj and epoxides, reduction of CO2 with organoborons, carboxylation of olefins with COj, and hydrocarboxy-lation of olefins with CO2 and Hj. They are fundamentally important reactions of carbon dioxide and have been intensively investigated experimentally and theoretically. This chapter is not intended to be a comprehensive review. Instead, we discuss the above-mentioned selected examples that we believe to be representative and important in the area of homogeneous catalysis of COj by transition metals from our own perspective. 

DMF can also be manufactured from carbon dioxide, hydrogen, and dimethylamine ia the presence of halogen-containing transition-metal compounds (18). The reaction has also been performed with metal oxides and salts of alkaU metals as promoters (19). 

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