Insertions and Migrations

Insertion and migration refer to the process in which an unsaturated molecule inserts to a metal-anion bond. The two ways of describing this elementary step have been depicted in Figure 2.2 and 2.3 In the platinum complex shown an acetyl fragment is formed from a co-ordinated CO and a methyl group, both attached to platinum. Clearly, the two reacting groups should occupy positions cis to one another, otherwise the reaction cannot occur [1]. 

Thermolysis of the azide (355) yielded 22% of the pyrano[4,3- ]-1,3,4-oxadiazine (121) via an intramolecular nitrene insertion and migration of the protecting group (Scheme 24) <82JOC523>. 

The lowering of carbonyl stretching frequencies by the introduction of has provided innumerable systems in which the course of carbon monoxide substitution, insertion, and migration could be readily followed by infrared. The advent of Fourier Transform nmr and high field nmr spectrometers has provided straightforward analysis not only of labeling, but of H, and as well as direct detection of many metal nuclei. The use of nmr appears to provide a particularly useful technique for the study of carbonyls in metal systems with I > 2 nuclei, such as cobalt, for which resonances are often broad or unobservable. 

The studies described above represent what is hoped is a comprehensive coverage of quantitative kinetic studies of insertion and migration reactions that have been reported. There are many other studies that relate to a very wide variety of insertion and migration processes from which mechanistic and semiquantitative kinetic inferences can be obtained, but space precludes their discussion here. Some rather arbitrarily chosen examples are appended. ... 

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