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Fundamentals of CO insertion

Because of the importance of the CO insertion into a transihon metal-carbon a-bond in relation to the transition metal-catalyzed carbonylation, the mechanism of the CO insertion has attracted considerable attenhon [1,2]. Through fundamental studies on model complexes, the route of CO insertion has been established for most transition metal complexes to be the one through alkyl migration mechanism [3-8]. While CO insertion can occur with various metal-heteroatom o-bonds, only insertion into metal alkyls (hydrocarbyls) will be discussed in this chapter. [Pg.374]

The generally accepted mechanism for CO insertion consists of the following steps (a) coordination of CO to the metal center (b) isomerization of the alkyl-carbonyl complex, if necessary, to bring the CO ligand adjacent to the alkyl ligand, [Pg.374]

The first convincing example of CO insertion into a metal-alkyl bond dates back to 1957, when Coffield demonstrated the reversible reaction of MnCH3(CO)5 with CO to give Mn(CH3CO)(CO)5 [9]. This CO insertion mechanism, which has been extensively studied by kinehc and/or spectroscopic means since the 1960s, has been regarded as a prototype of other CO insertion systems [10-12]. The important conclusions derived through these studies are summarized below. [Pg.374]

Recently, Ford et al. explored laser flash photolysis of the Mn(CH3CO)(CO)5 to give acyl intermediates relevant to carbonylation of MnCH3(CO)5 [21]. The time resolved infrared (TRIR) and time resolved optical (TRO) spectra of the long-lived acyl intermediate indicated that a dihapto acyl complex Mn(rj - [Pg.376]

For clarifying the factors influencing the ease of CO insertion and its reverse process, it is desirable to know the metal-carbon bond energies in the initial metal alkyl and the product metal acyl species. However, the presently available thermochemical data for the bond dissociation energies in acyl-transition metal complexes are not sufficient to allow us to advance a reasonable argument for the thermodynamic feasibilities of insertion and deinsertion processes [22-24], [Pg.377]


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