Carbon monoxide, addition reaction

Without other alternatives, the carboxyalkyl radicals couple to form dibasic acids HOOC(CH)2 COOH. In addition, the carboxyalkyl radical can be used for other desired radical reactions, eg, hydrogen abstraction, vinyl monomer polymerization, addition of carbon monoxide, etc. The reactions of this radical with chloride and cyanide ions are used to produce amino acids and lactams employed in the manufacture of polyamides, eg, nylon. 

At room temperature, Htde reaction occurs between carbon dioxide and sodium, but burning sodium reacts vigorously. Under controUed conditions, sodium formate or oxalate may be obtained (8,16). On impact, sodium is reported to react explosively with soHd carbon dioxide. In addition to the carbide-forrning reaction, carbon monoxide reacts with sodium at 250—340°C to yield sodium carbonyl, (NaCO) (39,40). Above 1100°C, the temperature of the DeviHe process, carbon monoxide and sodium do not react. Sodium reacts with nitrous oxide to form sodium oxide and bums in nitric oxide to form a mixture of nitrite and hyponitrite. At low temperature, Hquid nitrogen pentoxide reacts with sodium to produce nitrogen dioxide and sodium nitrate. 

Since 1985, several thousands of publications have appeared on complexes that are active as catalysts in the addition of carbon monoxide in reactions such as carbonylation of alcohols, hydroformylation, isocyanate formation, polyketone formation, etc. It will therefore be impossible within the scope of this chapter to review all these reports. In many instances we will refer to recent review articles and discuss only the results of the last few years. Second, we will focus on those reports that have made use explicitly of coordination complexes, rather than in situ prepared catalysts. Work not containing identified complexes but related to publications discussing well-defined complexes is often mentioned by their reference only. Metal salts used as precursors on inorganic supports are often less well defined and most reports on these will not be mentioned. 

Carbon monoxide will also add to aromatic coumpounds such as benzene and toluene. As the product of such an addition is an aldehyde and as aromatic aldehydes readily polymerize under the conditions necessary for the addition of carbon monoxide, the simple addition product is not obtained. These reactions have been performed in the author s laboratory using a technique similar to the addition to alcohols and alkyl halides. The products obtained are the same shellac-like resins that are obtained by treating the theoretically expected aldehyde with hydrogen fluoride under the same conditions. 

Metal-Halogen Counpounds. One of the few examples of an olefin insertion into a metal-halogen compound has been reported by Tsuji. The reaction, which also supports the idea that sigma-bonded metal-carbon compounds are intermediates in the palladium chloride-olefin oxidation reaction, was the addition of carbon monoxide to the ethylene palladium chloride 7r-complex in nonaqueous solvents to produce a moderate yield of 3-chloropropionyl chloride (96). 

Caution. The use of the volatile, toxic iron pentacarbonyl necessitates that all manipulations be carried out in a well-ventilated hood. In addition, the carbon monoxide evolved in the reaction is an odorless, extremely toxic gas, and care should be exercised that the apparatus vents into the best ventilated region of the hood. The compound 2-isocyano-l, 3-dimethylbenzene is a vile smelling, volatile solid that is best handled in a well-ventilated hood, using protective gloves. 

Strong mineral acids under forcing reaction conditions catalyze the addition of carbon monoxide and water to alkenes to form carboxylic acids 96 97... 

This reaction is important for a number of reasons. It is an industrial synthesis of aldehydes from alkenes by the addition of carbon monoxide and hydrogen in the presence of a cobalt catalyst. A prime example is the synthesis... 

This reaction in turn led to the discovery that aldehydes were formed by the further addition of carbon monoxide and hydrogen to alkenes, and was further developed as the oxo process for production of alcohols. The combination CO + H2 often is called synthesis gas. It is prepared by the reduction of water under pressure and at elevated temperatures by carbon (usually coke), methane, or higher-molecular-weight hydrocarbons ... 

Addition of carbon monoxide to hydrocarbon solutions of M2(OR)6 (M=M) compounds leads to M(CO)6 and alkoxy derivatives of Mo and W in oxidation states ranging from + 4 to +6. The course of the reaction depends upon the metal and the alkoxy ligand. In the case of the reaction between Mo2(OBu )6 and CO, the stoichiometric reaction (71) has been established.262... 

The following discussion deals not only with this reaction, but related reactions in which a transition metal complex achieves the addition of carbon monoxide to an alkene or alkyne to yield carboxylic acids and their derivatives. These reactions take place either by the insertion of an alkene (or alkyne) into a metal-hydride bond (equation 1) or into a metal-carboxylate bond (equation 2) as the initial key step. Subsequent steps include carbonyl insertion reactions, metal-acyl hydrogenolysis or solvolysis and metal-carbon bond protonolysis. 

One of the most interesting catalytic reactions to be discovered is the so-called oxo reaction. The oxo reaction consists of the catalytic addition of carbon monoxide and hydrogen to olefins to form, primarily, aldehydes possessing one carbon atom more than the original olefin. This hy-droformylation reaction was developed during World War II by Roelen and co-workers (22) in Germany. While they utilized solid Fischer-Tropsch cobalt-thoria catalyst, it became apparent to them that the hydroformylation reaction was probably a homogeneous catalytic process with either dicobalt octaearbonyl or cobalt hydrocarbonyl as the catalyst. 

Hydroformylation is a precious metal-catalyzed reaction of synthesis gas, a 1 1 mixture of hydrogen and carbon monoxide, and an olefinic organic compound to form aldehydes. The reaction was discovered by Otto Roelen in 1938 in experiments for the Fischer-Tropsch reaction [8]. In Scheme 3, hydroformylation of a terminal olefin is shown in which the addition of carbon monoxide can be conducted at both carbon atoms of the double bond, thus yielding linear (n) and branched (iso) aldehydes. 

In addition to carbon monoxide, other unsaturated compounds, for example isonitriles and acetylenes, can also insert into C-H bonds to give aldimines and substituted alkenes, respectively [12, 13]. Similar to carbonylation, high terminal selectivity for n-alkanes were also observed in these reactions. 

An important, but not yet understood, reaction of the dianion [Rhi2(CO)3o]2 is the reversible addition of carbon monoxide. Accurate measurements of the amount of absorbed gas indicate the stoichiometry (40,102) ... 

M. Torrent, M. Duran, and M. Sola, Density Functional Study on the Preactivation Scenario of the Dotz Reaction Carbon Monoxide Dissociation versus Alkyne Addition as the First Reaction Step, Organometallics 17, 1492-1501 (1998). 

A number of reactions of organomagnesium compounds, giving rise to new organomagnesium compounds, are covered in other chapters. They include addition to carbon-carbon multiple bonds (see Chapter 4), addition to isonitriles (see Section 5.4), addition to carbon monoxide (see Section 6.5), thiophilic addition to carbon-sulfur double bonds (see Chapter 7) and addition to carbenes (see Section 9.1). 

As early as 1938, Roelen discovered the cobalt-catalyzed hydroformylation of olefins, then known as the oxo reaction, which allowed the synthesis of aldehydes by addition of carbon monoxide and hydrogen to alkenes. Not long after this discovery it was found that cobalt, rhodium, ruthenium and platinum are also suitable as catalysts. However, because of the considerable price advantage for large scale applications in industry, cobalt catalysts are mostly used. Rhodium complexes, however, are... 

Example 5.2. Hydroformylation of propene [2]. Hydroformylation converts an olefin to an aldehyde of next higher carbon number by addition of carbon monoxide and hydrogen. The reaction is catalyzed by dissolved hydrocarbonyl complexes of transition-metal ions such as cobalt, rhodium, or rhenium. The carbon atom of the carbon monoxide can attach itself to the carbon atom on either side of the olefinic double bond, so that two aldehyde isomers are formed. If the catalyst also has hydrogenation activity, the aldehydes are converted to alcohols and paraffin is formed as by-product. For propene and such a catalyst the (simplified) network is ... 

Addition of carbon monoxide and hydrogen to an alkene linkage in the presence of cobalt catalysts gives aldehydes in an average yield of 50%. The reactions may be carried out in the usual hydrogenation apparatus. The poisonous properties of carbon monoxide and cobalt carbonyls call for considerable care. Compounds made by hydroformylation include cyclopentanealdehyde from cyclopentene (65%), /3-carbethoxy-propionaldehyde from ethyl acrylate (74%), and ethyl /3-formylbutyrate from ethyl crotonate (71%). 

An important modern example of homogeneous catalysis is provided by the Monsanto process in which the rhodium compound 1.4 catalyses a reaction, resulting in the addition of carbon monoxide to methanol to form ethanoic acid (acetic acid). Another well-known process is hydro-formylation, in which the reaction of carbon monoxide and hydrogen with an alkene, RCH=CH2, forms an aldehyde, RCH2CH2CHO. Certain cobalt or rhodium compounds are effective catalysts for this reaction. In addition to catalytic applications, non-catalytic stoichiometric reactions of transition elements now play a major role in the production of fine organic chemicals and pharmaceuticals. 

The nature of the surface site where acetylene hydrogenation occurs has been discussed extensively. It was proposed that two types of active sites are present on a Pd/Al203 catalyst. l One type promotes the hydrogenation of both triple and double bonds, whereas the other catalyzes only double-bond hydrogenation. This latter site can be poisoned by the addition of carbon monoxide to the reaction mixture as evidenced by the marked increase in reaction selectivity observed in the hydrogenation of acetylene in the presence of carbon monoxide.32.33 other modifiers can presumably act in the same way. 

Addition of carbon monoxide and water to an alkene, i.e. hydrocarboxylation, is catalyzed by a variety of transition metal complexes, including [Ni(CO)4], [Co2(CO)s] and [HaPtClg]. Unfortunately this reaction usually leads to mixtures of products due to both metal-catalyzed alkene isomerization and the occurrence of Irath Markownikov and anti-Markownikov addition of the metal hydride intermediate to the alkene. The commercially available zirconium hydride [(C5Hs)2Zr(H)Cl] can be used as a stoichiometric reagent for conversion of alkenes to carboxylic acids under mild conditions (equation 23). In this case the reaction with linear alkenes gives exclusively terminal alkyl complexes even if the alkene double bond is internal. Insertion of CO followed by oxidative hydrolysis then leads to linear carboxylic acids in very good yield. 

The synthesis of an ester by addition of carbon monoxide and an alcohol to an alkene, i.e. hydroesterification, has a fairly obvious relationship to the hydrocarboxylation described in Section 4.1.5, where water replaces the alcohol and a carboxylic acid is formed. Not surprisingly, therefore, the same types of catalysts, [Co2(CO)s], [H2PtCl6] and [Pd(PPh3)2Ch], are effective for both reactions. Unfortunately, the reaction usually requires very high pressures (200 bar) and necessitates the use of an autoclave. By varying the catalyst and reaction conditions a variety of linear, branched and cyclic alkenes can be carbonylated under these conditions to give the product in good yield (equation 32). Improved selectivity to the linear ester can be obtained by addition of SnCU to the catalyst system. 

Strictly related to catalytic reactions involving CO and H20 are reactions in which CO and alcohols, ROH, or CO and amines, R2NH, are used as building blocks. The catalytic addition of carbon monoxide and an alcohol to an olefin yields carboxylic esters (hydroesterification). Thus, the synthesis of methyl propionate from ethylene, CO, and methanol using a catalytic system composed of Ru3(CO)u and [PPh4]I (190°C, 20 bar C2H4, 45 bar CO, 2.5 hr, yield 74%, CT 1000) has been reported (323) ... 

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