Migratory insertions other ligands

Dihalocarbene ligands, like other neutral 2-e donor carbon ligands, are expected to participate in migratory-insertion reactions when bound adjacent to a rx-bound alkyl or hydride ligand. An example is provided by the following reaction (119) ... 

The main steps in the catalytic MeOH carbonylation cyde which were proposed for the Co catalysed process [2] have served, with some modification perhaps in the carbonylation of MeOAc to AC2O, to the present day and are familiar as a classic example of a metal catalysed reaction. These steps are shown in Eigure 5.1. They are of course, (i) the oxidative addition of Mel to a metal center to form a metal methyl species, (ii) the migratory insertion reaction which generates a metal acyl from the metal methyl and coordinated CO and (iii) reductive elimination or other evolution of the metal acyl spedes to products. Broadly, as will be discussed in more detail later, the other ligands in the metal environment are CO and iodide. To balance the overall chemistry a molecule of CO must also enter the cycle. 

Scheme 4) [57], In this case, when /V-vinyl imides were used as the olefin component, the predominant Heck product resulted from palladium migration. Other olefins, including vinyl esters, did not afford palladium migration products. While the reason for the success with Wvinyl imides is unclear, it has been pointed that these olefins may serve as ligands to stabilize the palladium and slow down the migratory insertion,... 

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