Carbon monoxide insertions catalysis

Carbon monoxide insertion and decarbonylation reactions of rhodium complexes have been studied mainly in the context of investigations concerned with catalysis. 

Radicals and carbenes ch37 ch38 metal to carbon are key steps Carbon monoxide inserts into metal-carbon bonds Palladium is the most important metal C-C, C-0, and C—N bonds can be made with Pd catalysis Cross-coupling of two ligands is common Allyl cation complexes are useful electrophiles ... 

The aminocarbonylation of phenols with carbon monoxide and ammonia has been achieved using palladium catalysis. After in situ conversion of the phenols to the corresponding nonaflates, oxidative addition to the palladium gives an aryl palladium complex which undergoes carbon monoxide insertion. Nucleophilic attack of ammonia results in the formation of the benzamide. ... 

In this chapter we will discuss some aspects of the carbonylation catalysis with the use of palladium catalysts. We will focus on the formation of polyketones consisting of alternating molecules of alkenes and carbon monoxide on the one hand, and esters that may form under the same conditions with the use of similar catalysts from alkenes, CO, and alcohols, on the other hand. As the potential production of polyketone and methyl propanoate obtained from ethene/CO have received a lot of industrial attention we will concentrate on these two products (for a recent monograph on this chemistry see reference [1]). The elementary reactions involved are the same formation of an initiating species, insertion reactions of CO and ethene, and a termination reaction. Multiple alternating (1 1) insertions will lead to polymers or oligomers whereas a stoichiometry of 1 1 1 for CO, ethene, and alcohol leads to an ester. 

Insertion of carbon monoxide and alkenes into metal-carbon bonds is one of the most important reaction steps in homogeneous catalysis. It has been found for insertion processes of platinum [16] that the relative positions of the hydrocarbyl group and the unsaturated fragment must be cis in the reacting complex [17], The second issue concerns the stereochemical course of the reaction, insertion versus migration as discussed in Chapter 2.2. 

While studying the reaction of adamantane with carbon monoxide under super-acidic catalysis, formylation (formation of 1-adamantanecarboxaldehyde) was found by Olah and co-workers447 to effectively compete with Koch—Haaf carboxylation (formation of 1-adamantanecarboxylie acid, major product formed in 60-75% yield). On the basis of results acquired by the reaction of 1,3,5,7-tetradeuteroadamantane, formylation was interpreted by insertion of the formyl cation into the tertiary C—H cr-bond [Eq. (5.163)]. 

Elementary steps involving insertion or migration reactions are of prime importance for catalysis employing alkenes and carbon monoxide. Two examples taking place on a platinum centre have been depicted in Figs. 4.18 and 4.19. In these reactions an acetyl fragment is formed on the platinum centre from a coordinated CO and a methyl group. The important mechanistic difference... 

Reaction of [Mn(R)(CO)j] with neutral nucleophiles is by far the most widely studied type of reaction for [Mn(R)(CO)s] compounds. The reaction usually involves addition of the neutral neucleophile, L, and is accompanied by CO insertion/alkyl migration to form an acyl species [Eq. (29)]. L is usually a tertiary phosphine (PR3), an alkylated amine (RNH2), or free carbon monoxide. Besides being a carbon-carbon bond forming reaction of fundamental importance, alkyl migration reactions of transition metal alkyl species have direct relevance to catalysis, especially for the 0X0 or hydroformylation process (2), the Monsanto acetic acid synthesis (2), and the synthesis of ethylene glycol (94). 

While wanning the catalysis mixture to 55 C (Step D, Scheme 1) leads to no other observable reaction intermediates, the generation of intermediate 8 would allow the series of steps shown in Scheme 1. Insertion of the coordinated CO into the palladium-carbon bond would lead to the overall coupling of acid chloride, imine and carbon monoxide in conq>lex 10. The subsequent loss of HCl from 10, either via direct deprotonation or P-H elimination, would form the a-amide substituted ketene 11. The latter is known to be in rapid equilibrium with its cyclic mesoionic l,3-oxazolium-5-oxide tautomeric 12 (14). These steps would lead to the liberation of the Pd(0) catalyst, which can return to the catalytic cycle. 

Aryl-, alkenyl- and alkynylpalladium species readily undergo carbonylation reactions because carbon monoxide as a loosely bonded ligand can reversibly insert into any palladium-carbon bond [110]. Thus, 2-allyl-l-iodocyclopentene (148), under palladium catalysis, reacts with carbon monoxide in two modes, depending on the excess of carbon monoxide and the catalyst cocktail (Scheme 3-39) [110a]. With a slight excess (1.1 atm of CO) in the presence of [Pd(PPh3)4] in tetrahydrofuran, 148 cyclized with one CO insertion to yield 3-methylenebicyclo[3.3.0]oct-l(5)-en-2-one (152), and under 40 atm of CO with [Pd(PPh ,)2Cl2] in benzene/acetonitrile/methanol, methyl 2- 3 -(2 -oxobicyclo[3.3.0]oct-1 (5 )-enyl) acetate 149 after two CO insertions (Scheme 3-39). 

Another application found for phospholes in catalysis is in the insertion of carbon monoxide into a carbon-halogen bond <86POL9ll>. rrans-Dichlorobis(l,2,5-triphenylphosphole)palladium(II) was effective as a catalyst at atmospheric pressure and was superior to the complex based on triphenylphosphine (Equation (72)). 

The insertion of carbon monoxide has not yet been achieved. Bis(ir-allyl)-nickel reacts with butadiene to form cyclododecatriene. The allylic groups may also be displaced by cycloocta-l,5-diene or cyclooctatetraene. Wilke regards (LVIII) as formally a complex of Ni(II), assuming that during the catalysis there is a constant and reversible change in the formal oxidation... 

Kinetic studies of this process do indeed show the catalysis being first order in the concentration of the ruthenium cluster and inversely dependent on the partial pressure of carbon monoxide indicating thus that the most important intermediate in the reaction is the coordinately unsaturated species H4Ru4(CO)ii. Coordinately unsaturated sites in the catalyst would be achieved, in this case, by the dissociation of a CO-ligand. The catalytic effect of the unsaturated intermediate depends on the reversible insertion of ethylene into the Ru-H bond. However there is competition between this insertion and the addition of carbon monoxide or H2 for obtaining the starting compound or the hexahydride H6Ru4(CO)n respectively. 

---