Insertion reactions involving

In that complex, it may be that water reacts with the coordinated C2H4 to produce a cr-bonded CH2CH2OH group rather than an insertion reaction involving an OH group. The aldehyde is formed as H+ is lost, and the palladium is produced as shown in Eq. (22.31). The palladium chloride catalyst can be recovered (the price of palladium is almost 500/oz as this is written) by the reaction with CuCl2. 

Under the influence of nickel catalysts, 1,5- and 1,6-dienes undergo isomerization and cyclization, preferably to five-membered ring compounds. The cyclization takes place probably via an intramolecular insertion reaction ( , ) involving a ir-5-alken-l-ylnickel complex such as 33, Table III, and 34, Table IV formed by Ni — C, and Ni — C2 additions... 

In contrast to this, according to the T-Cat mechanism, the initiator forms an ester with the alkene which incorporates the next monomer molecule by means of an insertion reaction involving a 6-membered cyclic transition state. 

Jhe reaction mechanism of the various metal complexes clearly have much in common. The recently recognized insertion reaction appears to be a particularly good example of a reaction which is general among the metal compounds. In the following discussion I intend to point out the generality of the insertion reaction with examples from the literature and from our own wrork. The most complete series of substantiated insertion reactions involves the organocobalt carbonyl complexes, and these reactions will form the nucleus of the discussion. 

In many of these systems, the postulated olefin complex intermediate would be labile. Therefore, its role as a pre-equilibrium intermediate is not terribly relevant to the kinetic problem. I think the relevant feature is whether the favorable paths in these insertion reactions involve the first or second type of transition state. This perhaps de-emphasizes the question of whether or not a 7r-bonded intermediate is involved but certainly does focus attention on the question of whether a coordinated unsaturated species is involved as a reactant. This is because the first type of transition state will require two coordination positions and hence involve the elimination of some other ligand before it can form, whereas the second will not. I don t know the answer to this question but this is how I would formulate the problem. 

We discussed this catalysis recently (141st National Meeting of the American Chemical Society, March 1962) in terms of an olefin insertion reaction involving a Pt(II) olefin complex (3). We found that catalysis was only accomplished by platinum compounds capable of coordinating olefins. For example, substitution by tertiary phosphines blocks coordination by olefins and greatly reduces the catalytic activity of Pt(II). The substitution by phosphines does not affect the ability of the complexes to cleave the Si—H bond, however. The hindering of a catalytic reaction by blocking coordination sites is a common occurrence and is, I think, a persuasive... 

A rather unique synthetic example based on the well-known pyrrole-pyridine carbene insertion reaction involves the following ring expansion.16... 

The known C02 insertion reactions involving metal-carbon bonds have all resulted in carbor. -carbon bond formation with possibly one exception. Infrared spectral and chemical evidence has been presented for the formation of the metallocarboxylate ester Co(C03) (COOEt)(PPh3), n = 0.5-1.0 from the reaction of Co(CO)(C2H5XPPh3)2 with carbon dioxide from Vol-pin s laboratory (68). Although these studies are not conclusive for abnormal C02 insertion, metallocarboxylate esters are well-known compounds which result from the nucleophilic addition of alkoxides on the carbon center in metal carbonyls (69). 

A general review of insertion reactions involving metal-carbon bonds, including those with C02, has recently been published by Alexander (90). 

The first and third steps are insertion reactions involving dichlo-romcthyllithiuni. 

The first theoretical rationalization of an NMR/reactivity correlation was offered for an insertion reaction involving iron complexes 2, equation 2. With increasing bulkiness of the alkyl ligands at iron, PPh3-induced insertion of CO into the Fe-... 

Surveyed in this section are known SOg insertion and desulfination reactions. Kinetic and stereochemical results already discussed in Sections III-V, as well as the cycloaddition processes treated in Section V, have been given a cursory mention for the sake of completeness. The insertion reactions involving bonds other than M—C are omitted. Also excluded are all aspects of the chemistry of metal sulhnate complexes except sulfur dioxide insertion and desulfination. Readers interested in alternative methods of synthesis and in the physical and chemical properties of these and related compounds are referred to a recent review 128). 

Heck (149) has discussed several alkyne insertion reactions involving alkyl- and acyl-tetracarbonylcobalt complexes. Most reactions seem to give tricarbonyl-7T-(penteno-4-lactonyl)cobalt complexes and numerous other products. The reaction of CFaC CCFs with HCo(CO)4 results in reduction of the alkyne (85), but Co2(CO)e(HC2H) is formed (150) in the related reaction of HC—CH with HCo(CO)4 in methanol. 

Insertion reactions involving metal alkoxides are also known. For example, carbon dioxide is known to react with some metal alkoxides as shown in equation (12). The formation of a bidentate ligand is a significant thermodynamic driving force for some of these reactions. The isoelectronic aryl and alkyl isocyanates and carbodiimides can react similarly. Insertion reactions involving alkenes and carbon monoxide are known for platinum alkoxides. 

A similar analysis of the (HPdCO)+ - (PdCHO)+ reaction (3 showed that in these systems, and in agreement with known experimental data (41), the d - tzqq back donation effects arc rather weak and that they should not interfere significantly in the theoretical description of insertion reactions involving Pd(II) transition metal... 

An interesting insertion reaction involves EtZnCH2l and p-keto carbonyl compounds. The reaction of this reagent with A,A-dibutyl-3-oxobutanamide, for example, gives the methylene insertion product N,N-dibutyl 4-oxopentanamide. ... 

Accurate quantum dynamical studies of insertion reactions involving H2 molecules are now feasible for a. single potential energt surface and we have obtciined the same degree of comparison with experiment as for abstraction reactions ten years ago. The computational effort is however much larger. O + ff2 being roughly 100 times more expensive than F -t H2. 

Most important for scientific and technological relevance are the CO insertion reactions involving transition metals. The first of these reactions, the carbonylation of methyl- and phenylpentacarbonylmanganese(I) to the corresponding acetyl and benzoyl derivatives, according to reaction (b), was discovered in 1957 ... 

Expected insertion reactions involving aldimides or ketimines, RCH=NR or RR"C=NR, related to those of the isoelectronic aldehydes or ketones, are unknown. There has been much interest in compounds having (p-p) rt bonds between C, N, O, or S, on the one hand, and B, Si, Ge, or Sn, on the other. Few compounds stable at ambient temperature have been isolated. Substantial evidence for their existence, however, comes from spectroscopy and kinetics. Trapping experiments support their existence as well, as illustrated by insertion reactions of a transient molecule 5 ... 

This reaction is analogous to the sulfur insertion reaction involved in biotin biosynthesis, and LipA and BioB show significant sequence similarity [145,146]. 8-Mercapto-octanoic acid and 6-mercapto-octanoic acid are intermediates... 

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