Monoxide insertion

7t-Allyl complexes also may undergo insertion reactions (6-81), that is, when coupling of two allyl groups does not occur (6-82). 

Carbon monoxide usually displaces the olefin in olefin 7i-complexes. A similar displacement reaction occurs with 7T-C5H5 and complexes. 

Oxidation of the metal from Fe(II) to Fe(III) greatly increases both the rate and equilibrium constant (Kgq) for the CO insertion in equation (25). Electrochemical studies show that is —10 times greater for the Fe(III) analogues, and that this is largely due to an increase in the forward rate constant. This oxidatively induced insertion is not catalytic because the acyl product in equation (25) is more easily oxidized than the reactant. However, the carbonylation shown in equation (26) is subject to 

Somewhat akin to oxidatively induced insertions are the ones promoted by electrophilic reagents that can bind to a carbonyl oxygen in the acyl intermediate. This was nicely illustrated in a recent study in which (16) in methylene chloride was observed to react rapidly with simple alkali-metal and alkaline-earth salts to produce (17) in which the acyl oxygen is stabilized 

There is still debate concerning the bonding mode of the acyl in the coordinatively unsaturated intermediate usually assumed to occur during CO insertions. An IR study of [Mn(CO)4(COMe)] and [CpFe(CO)(COMe)] in methane matrices at 12 K suggests that, at least under these conditions, the bonding is -acetyl and not rj -acetyl.  

Equation (28) gives the usual mechanism for CO insertion in a polar solvent (S). Reactions (29) and (30) with a variety of alkyl and aryl phosphines show clearly that increasing size of the nucleophile lowers the value of Similarly, PPhj-induced CO insertion in 

The rate of carbonylation of [Mn(CO)5CH2X] in acetonitrile at 24°C is independent of CO pressure over the range 750-1500 psi, and is three times greater for X = OSiMes than for X = OMe. The decarbonylation 

The effect of substituents (X) on the rate of benzyl group migration according to equation (33) has been studied. In CH3CN solvent at high 

PPh3 concentrations a limiting rate is reached that presumably represents rate-determining benzyl migration to give the usual acyl type intermediate that is then trapped by nucleophile. The limiting rate constant increases 

Both CO and P(OCH2)3CMe have been used to induce CO insertion in c/s-[MeMn(CO)4( CO)]. In THF/acetone at 25°C an analysis of the CO positional isomers in the products shows that migration proceeds through a square-base pyramid with a basal acetyl group as shown in complex 22. Solvent may also be coordinated and/or the acetyl group may 

Lewis acids such as AIX3 are known to induce rapid alkyl migration in metal carbonyls. Equation (36) shows the product formed in the absence of nucleophile. Subatmospheric CO converts 23 to [Mn(CO)5COMe AlX3]. Comparison of the rate of reaction (36) to the 

Several other examples of CO insertions induced by electrophilic reagents have appeared. Formation of the hydroxy carbene in equation (38) is promoted by HCl. 

Assuming the lower pathway, ku is equal to fci/c2//c i. Activation parameters were also determined. 

Enthalpies for reactions shown in Eq. (22) have been measured, where R = Me, Et, and L = several P-donors. For phosphines they become more favorable as 

The kinetics of the reactions (25) have been reported to be first order in [PPh3] in toluene, THF, and CH2CI2 (R = Me and P-XQH4 X = H, Me, Cl). Values 

R = Ph than for R = Me. Reactions in MeCN and MeN02 are considerably faster and show limiting rates at high [PPhj]. Reactions are faster with more electron-donating substituents, X. 

Insertion of CO into the Ta—Si bond in [Cp Cl3TaSiMe3] occurs to form a thermally unstable [Cp Cl3Ta(i7 -COSiMe3)] complex which undergoes some interesting further insertion processes. Reaction of CO with [(OEP)Rh]2 occurs very readily to form an equilibrium mixture of the adduct [ (OEP)Rh 2CO] (in which the CO is terminally bound to a Rh atom), and the insertion products [(0EP)RhC(0)Rh(0EP)] and [(0EP)RhC(0)C(0)Rh(0EP)], where OEP = octaethylporphyrin. Values of equilibrium constants, and AH° and A5 values for all the equilibria are reported and the formation of the adduct, the monoinsertion product, and the double insertion product are all exothermic with AH = -10 1, -12 2, and -21 2 kcal mol , respectively. The major factor involved in 

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Pyrrohdinone (2-pyrrohdone, butyrolactam or 2-Pyrol) (27) was first reported in 1889 as a product of the dehydration of 4-aminobutanoic acid (49). The synthesis used for commercial manufacture, ie, condensation of butyrolactone with ammonia at high temperatures, was first described in 1936 (50). Other synthetic routes include carbon monoxide insertion into allylamine (51,52), hydrolytic hydrogenation of succinonitnle (53,54), and hydrogenation of ammoniacal solutions of maleic or succinic acids (55—57). Properties of 2-pyrrohdinone are Hsted in Table 2. 2-Pyrrohdinone is completely miscible with water, lower alcohols, lower ketones, ether, ethyl acetate, chloroform, and benzene. It is soluble to ca 1 wt % in aUphatic hydrocarbons. 

A simplified mechanism for the hydroformylation reaction using the rhodium complex starts by the addition of the olefin to the catalyst (A) to form complex (B). The latter rearranges, probably through a four-centered intermediate, to the alkyl complex (C). A carbon monoxide insertion gives the square-planar complex (D). Successive H2 and CO addition produces the original catalyst and the product ... 

Insertion Reactions of Transition Metal-Carbon -Bonded Compounds I Carbon Monoxide Insertion... 

II. Carbon Monoxide Insertion. General Considerations and Background... 

CARBON MONOXIDE INSERTION. GENERAL CONSIDERATIONS AND BACKGROUND... 

Carbon monoxide insertion reactions may be represented by the equation ... 

Carbon monoxide insertions are intramolecular. It therefore follows that an important requirement for occurrence of these processes is presence of the CO and R in the reacting complex in a suitable position to combine. Accordingly, compound (I) does not react with CO under ambient conditions (105). The dinuclear [MeCo(DH)2]2 (DH = dimethylglyoximate) reacts with CO, but not by insertion, to give (II) in solution (125). Forma-... 

Carbon monoxide insertion is not restricted to transition metal-carbon bonds, although M—C is by far the most common substrate involved. Reactions have also been reported which lead to insertion of CO into M—O (114) and M—N (199) bonds. 1,1-Additions of M—H (27, 114) and M—M (104) linkages to CO have been postulated, too. However, direct replacement of CO, without rupture of the W—H bond, is indicated for the reaction between CpW(CO)3H (or -D) and PPhj (5) ... 

This chapter is concerned initially with kinetic results and mechanistic interpretations of the CO insertion (Section III) and extrusion (Section IV) reactions. A discussion of the stereochemical data follows (Section V), and a comprehensive survey of these reactions by the triads (Section VI) rounds out the review. Carbon monoxide insertion reactions were discussed in 1967 by Basolo and Pearson (21). Since then they have been mentioned in several reviews (49, 118, 203, inter alios) but have not been treated comprehensively. 

Again, this aspect of carbon monoxide insertion has not received much attention. Hart-Davis and Mawby (108), in a comparative study, examined the reaction of 7r-C9H7Mo(CO)jMe (VII) with various P donor ligands. They find that, in THF, (VII) undergoes CO insertion, via a solvent-assisted... 

The intermediate M(COR) is the same as that for carbon monoxide insertion. It may be a coordinatively unsaturated solvated or unsolvated a-acyl or, alternatively, a 7r-acyl. It is of interest that photolysis of MeCOMn(CO)j in an Ar matrix at 15°K produces what appears to be a trigonal bipyramidal (Cj ) MeCOMn(CO)4 209). 

For the recently reported carbon monoxide insertion reaction (94)... 

A complete description of stereochemistry of the carbon monoxide insertion and decarbonylation requires knowledge of configurational changes at the metal and a-carbon. Calderazzo and Noack (54) showed that the optical activity of the equilibrium mixture... 

Carbon monoxide insertion reactions of CpFe(CO)LR are not common. The complex CpFe(CO)(PPh3)Me can be converted to the acetyl monocarbonyl with CO in refluxing petroleum ether ( 100°C) (227). By contrast, ultraviolet light-promoted reaction between CpFe(CO)(PPh3)R (R = Ph orp-CfiH4F) and CO yields CpFe(CO)2R (188). 

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

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