Migratory CO insertion reaction

Thus, the migratory CO insertion reaction on the iridium center, which is the rate-determining step of the iridium catalytic cycle, is accelerated by T ligand dissociation. These results tend to rationalize the seminal and inspired observations of Forster at Monsanto Co. [25]. 

Kinetic and Mechanistic Studies of Stoichiometric Reaction Steps 3.3.2.1 Migratory CO Insertion Reactions of Metal Alkyls... 

Scheme 1 General reaction pathway for the iodomethane oxidative addition and successive migratory CO insertion reactions in Vaska-type compounds Y=P ), As (2))...

The Rh-catalyzed ring-expansion reaction of thiazolidine 246 in the presence of a catalytic amount of KI (2 mol%) at 180°C and 65 atm of CO gave thiazolidinone 251 in 56-88% yields. Formation of thiomorpholinone 252 was not observed at all. Thus, a proposed mechanism of this reaction involves the elimination of a ketene molecule from a key intermediate 248 to form rhodathiazolidine complex 249, which undergoes migratory CO insertion, followed by reductive elimination to yield thiazolidinone 251 (Scheme 36). ... 

A classic example of a CO insertion reaction (called migratory insertion for reasons to be explained later) is found in Ihe work of Noack and Calderazzo.153... 

The catalytic cycle involves the same fundamental reaction steps as the rhodium system oxidative addition of Mel to Ir(I), followed by migratory CO insertion to form an Ir(III) acetyl complex, from which acetic acid is derived. However, there are significant differences in reactivity between analogous rhodium and iridium complexes which are important for the overall catalytic activity. In situ spectroscopy indicates that the dominant active iridium species present under catalytic conditions is the anionic Ir(III) methyl complex, [IrMe(CO)2l3] , by contrast to the rhodium system where the dominant complex is [Rh(CO)2l2] - PrMe(CO)2l3] and an inactive form of the catalyst, [Ir(CO)2l4] represent the resting states of the iridium catalyst in the anionic cycles for carbonylation and the WGSR respectively. At lower concentrations of water and iodide, [Ir(CO)3l] and [Ir(CO)3l3] are present due to the operation of related neutral cycles . 

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