Migratory insertions carbon monoxide

Organometallic Compounds. Mononuclear carbon monoxide complexes of palladium are relatively uncommon because of palladium s high labihty, tendency to be reduced, and competing migratory insertion reactions in the presence of a Pd—C bond (201). A variety of multinuclear compounds... 

Alkylation of the anion 2 with iodomethane or other haloalkanes provides alkyldicarbonyl(t/5-cyclopentadienyl)iron complexes such as 53,0 (see also Houben-Weyl, Vol. 13/9a, p 209). Migratory insertion of carbon monoxide occurs on treatment with phosphanes or phosphites9 -11 (see also Houben-Weyl, Vol. d3/9a, p257) to provide chiral iron-acyl complexes such as 6. This is the most commonly used preparation of racemic chiral iron-acyl complexes. 

Another route to enantiomcrically pure iron-acyl complexes depends on a resolution of diastereomeric substituted iron-alkyl complexes16,17. Reaction of enantiomerically pure chloromethyl menthyl ether (6) with the anion of 5 provides the menthyloxymethyl complex 7. Photolysis of 7 in the presence of triphenylphosphane induces migratory insertion of carbon monoxide to provide a racemic mixture of the diastereomeric phosphane-substituted menthyloxymethyl complexes (-)-(/ )-8 and ( + )-( )-8 which are resolved by fractional crystallization. Treatment of either diastereomer (—)-(/J)-8 or ( I )-(.V)-8 with gaseous hydrogen chloride (see also Houben-Weyl, Vol 13/9a, p437) affords the enantiomeric chloromethyl complexes (-)-(R)-9 or (+ )-(S)-9 without epimerization of the iron center. 

A catalyst used for the u-regioselective hydroformylation of internal olefins has to combine a set of properties, which include high olefin isomerization activity, see reaction b in Scheme 1 outlined for 4-octene. Thus the olefin migratory insertion step into the rhodium hydride bond must be highly reversible, a feature which is undesired in the hydroformylation of 1-alkenes. Additionally, p-hydride elimination should be favoured over migratory insertion of carbon monoxide of the secondary alkyl rhodium, otherwise Ao-aldehydes are formed (reactions a, c). Then, the fast regioselective terminal hydroformylation of the 1-olefin present in a low equilibrium concentration only, will lead to enhanced formation of n-aldehyde (reaction d) as result of a dynamic kinetic control. 

This article reviews recent results on the chemical, spectral and structural properties of bis(pentamethylcyclopentadienyl) thorium and uranium dihaptoacyl complexes produced by migratory insertion of carbon monoxide into actinide-carbon sigma bonds. 

Zirconium hydride reactivity with carbon monoxide demonstrates the strong driving force toward products with a Zr-O bond. Indeed, the facility of the CO migratory insertion into Zr-C and especially Zr-H bonds may be from a carbonyl oxygen-zirconium interaction that stabilizes the transition state to the acyl and formyl complexes. 

Organometallic Compounds. Mononuclear carbon monoxide complexes of palladium are relatively uncommon because of palladium s high lability, tendency to be reduced, and competing migratory insertion reactions in the presence of a Pd—C bond (201). A variety of multinuclear compounds are known (202), including [Pd2Cl4(CO)2] [75991-68-3], [Pd3(P(C6H5)3)3(CO)3] [36642-60-1], and [Pd7(P(CH3)3)7(p3-CO)3(p2-CO)4] [83632-51-3]. 

The key intermediate in the reduction of metal ions by carbon monoxide and water is the hydroxycarbonyl (18). Initially (18) was proposed to form by a migratory insertion of CO into a M—OH bond, but more recent studies have favored a direct attack of water or hydroxide on a coordinated carbonyl (4,62). This latter view is in accord with the expected reactivity of coordinated CO toward nucleophiles. Intermediate (18) may then decarboxylate to give C02 and either a reduced metal ion or a metal hydride, as in (29) and (30), respectively. 

The mechanism of this three-component coupling reaction is probably analogous to the aforementioned insertion of acyl chlorides (above). One can imagine assembling an intermediate acylpalladium species either by oxidative addition to an acyl chloride or, in this case, by oxidative addition to the aromatic iodide followed by migratory insertion into carbon monoxide. Once formed, the acylpalladium intermediate can insert into the SCB to furnish a 7-(chlorosilyl)propyl ketone, which cyclizes in the presence of the amine to afford cyclic enol ethers. 

Different types of migratory insertions are exemplified by reactions 10, 11, and 12 in the Table II. An evaluation scheme is given in Matrix 6. In the present study we consider this reaction according to its general mechanism, shown in Eq. (6), where L is a neutral ligand (olefin, carbon monoxide, carbene, etc.) which becomes X (anionic c-donor ligand). X is also an anionic a-donor ligand. 

Migratory insertion is the principal way of building up the chain of a ligand before elimination. The group to be inserted must be unsaturated in order to accommodate the additional bonds and common examples include carbon monoxide, alkenes, and alkynes producing metal-acyl, metal-alkyl, and metal-alkenyl complexes, respectively. In each case the insertion is driven by additional external ligands, which may be an increased pressure of carbon monoxide in the case of carbonylation or simply excess phosphine for alkene and alkyne insertions. In principle, the chain extension process can be repeated indefinitely to produce polymers by Ziegler-Natta polymerization, which is described in Chapter 52. 

Carbonylation (the addition of carbon monoxide to organic molecules) is an important industr process as carbon monoxide is a convenient one-carbon feedstock and the resulting metal-acyl cor plexes can be converted into aldehydes, acids, and their derivatives. The 0X0 process is the hydr formylation of alkenes such as propene and uses two migratory insertions to make higher val aldehydes. Though a mixture is formed this is acceptable from very cheap starting materials. 

The glyoxylative-decarbonylative coupling rationalizes as follows (Scheme 27). After the oxidative addition of indole-3-glyoxylyl chloride 38, adduct 39 undergoes a migratory de-insertion and elimination of carbon monoxide furnishing the acyl-Pd... 

In order to more fully understand the mechanism for the promotion of carbonylation in the Cativa process, a recent comprehensive study utilizing spectroscopic methods and ab initio calculations was carried out to explore the role of the promoters. The acceleration of the migratory insertion step is the result of iodide abstraction from the iridium center in c,m-[fr(CO)2l3Me] by the promoters to yield the neutral species [Ir(CO)3l2Me] in the presence of CO. It was determined that the migratory insertion of carbon monoxide in [fr(CO)3l2Me] is 700 times faster than for the anionic species [fr(CO)2l3Me]. ... 

Acylzirconocene chlorides are easily accessible in a one-pot procedure through the hydrozirconation see Hydrozirconation) of alkene or alkyne derivatives with the Schwartz s reagent and subsequent migratory insertion see Migratory Insertion) of carbon monoxide into the alkyl- or alkenyl zirconium bond. The stability of the acylzirconocene chlorides is remarkable at room temperature, and consequently allows many applications in organic synthesis. 

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