Alkyne complexes with carbon monoxide

Finally, manganese carbonyl complexes also show potential for effecting interesting phase transfer catalyzed carbonylation reactions. Alkynes react with carbon monoxide and methyl iodide in methylene chloride, using 5N NaOH as the aqueous phase, benzyl-triethylammonium chloride as the phase transfer catalyst, and either bromopentacarbonylmanganese or dimanganese decacarbonyl to afford... 

Reactions of the (RC2H)Co2(CO)6 complexes with carbon monoxide under pressure give lactone complexes (reducible to y-butyrolactones ) by insertion of two CO groups into the Co-C bonds (eq 37) the further stepwise insertion of CO and alkyne provides the mechanism for the efficient Co2(CO)g-catalyzed synthesis of 2,2 -bifurylidene-5,5 -diones (eq 38). Under relatively mild conditions and with a 1 1 ratio of C2H2 CO, the extended bifurandiones of eq 39 also become significant products. ... 

The thermal benzannulation of Group 6 carbene complexes with alkynes (the Dotz reaction) is highly developed and has been used extensively in synthesis [90,91]. It is thought to proceed through a chromium vinylketene intermediate generated by sequential insertion of the alkyne followed by carbon monoxide into the chromium-carbene-carbon double bond [92]. The realization that photodriven CO insertion into Z-dienylcarbene complexes should generate the same vinylketene intermediate led to the development of a photochemical variant of the Dotz reaction (Table 14). 

Complex condensation products are obtained by reaction of the alkyne complex with excess of 3,3-dimethyl-l-butyne, which yields two isomeric products of formulas Ru3(CO)6[HC2C(Me)3-COCH2CMe3][HC2CMe3]2 (125). The X-ray structure of one of those adducts (Fig. 19) shows that both dimerization of two alkyne molecules and the insertion of carbon monoxide into the alkyne metal bonds have occurred. The Ru-Ru distances of 2.820,2.828, and 2.686 A in the ring are of interest. The value of 2.686 A is one of the shortest found in a... 

Alkenyl, allyl, and aryl halides undergo oxidative addition to Pd° complexes to form alkenyl-, allyl-, and aryl-palladium a-complexes which then react with carbon monoxide, alkenes and alkynes. 

For the Pauson-Khand [2+2+1] cycloaddition175 of alkyne, alkene, and carbon monoxide, as well as being promoted by Co2(CO)8, Portnoy et al.176 synthesized a dendronized support modified with 2- and 4-(diphenylphosphino)benzoic acid groups Co2(CO)8 was then incorporated into the support. A notable increase in catalytic activity and selectivity for the intramolecular Pauson-Khand reaction was found for the Co complexes immobilized on the second-and third-generation dendron-functionalized polystyrene, when compared with the analogous nondendronized support. 

Besides [m + n] cycloadditions and [m 4- m + m +. ..] cyclo- and cocyclooligomerizations of alkenes, dienes or alkynes (see Sections 1.5.8.3.5, and 1.5.8.3.6.), transition metal complexes can also catalyze the cycloaddition of more than two different components. Most important is carbonylative ring synthesis with carbon monoxide as the C, unit. Several methods of this type use transition metals stoichiometrically, others catalytically. For some of the stoichiometric methods, developments towards catalytic versions are under way (e g., the Pauson-Khand reaction, see below). 

The discussed reactions of carbene and carbyne complexes show that they have essential significance as catalysts or unstable transient intermediate compounds in such catalytic processes as metathesis of olefins and other unsaturated compounds, Fischer-Tropsch synthesis, syntheses of cyclopropanes from diazoalkanes and olefins, and polymerization of olefins and alkynes as well as in organic synthesis. Except for alkynes [reaction (5.132) ] some compounds containing double bonds react with carbon monoxide and carbene ligands to form bonds with those groups. Examples of such compounds are enamines, ynamines, and Schiff bases. The JV-vinylpyrrolidone (enamine), methoxyphenylcarbene, and excess of CO (higher pressure) react to furnish enaminoketone. 

The cobaltacyclopentadiene is converted on heating into a cyclobutadiene derivative. Treatment with carbon monoxide affords a cyclopentadienone complex. It is therefore probably an intermediate in the formation of these products from CpCo(CO) (L = CO) and alkynes. 

The catalytic hydrocarbonylation and hydrocarboxylation of olefins, alkynes, and other TT-bonded compounds are reactions of important industrial potential.Various transition metal complexes, such as palladium, rhodium, ruthenium, or nickel complexes, have widely been used in combination with phosphines and other types of ligands as catalysts in most carbonylation reactions. The reactions of alkenes, alkynes, and other related substrates with carbon monoxide in the presence of group VIII metals and a source of proton affords various carboxylic acids or carboxylic acid derivatives.f f f f f While many metals have successfully been employed as catalysts in these reactions, they often lead to mixtures of products under drastic experimental conditions.f i f f f In the last twenty years, palladium complexes are the most frequently and successfully used catalysts for regio-, stereo-, and enantioselective hydrocarbonylation and hydrocarboxylation reactions.f ... 

The reaction of butadiene with alkynes to give cyclodecatrienes is catalysed by zerovalent nickel complexes. Evidence that these reactions proceed in a stepwise manner and involve an aw-bisallyl-Cg nickel complex has now been obtained. Thus addition of Et02CC CC02Et to the aco-octadienediylnickel complex (40) at — 30 °C gives a yellow complex (41) which on treatment with carbon monoxide gives the cyclodecatriene derivative (42) (Scheme 10). ... 

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