Subject migratory insertion

When the substrate is a triflate, or when a halide is subjected to appropriate reaction conditions in the presence of a halide scavenger (such as silver or thallium salts), the reaction proceeds via the cationic manifold. After oxidative addition, dissociation of X yields cationic intermediate 67. Alkene coordination provides 68 and migratory insertion delivers 69. /S-Hydride elimination then yields the desired product 66. Of importance in the pathway 62- 7— 68— 69— 66 is that both phosphines maintain contact with the metal throughout the process. This is ostensibly the factor responsible for the high enantioselectivities observed for reactions that are thought to proceed along this pathway. This contrasts with the course of events in the neutral pathway, where phosphine dissociation is thought to be responsible for low enantioselectivities. 

The transformation of an alkylmetal carbonyl complex into a metal-acyl complex is one of the most common types of migratory insertion reactions (Equation 9.3). Examples of CO insertion into metal-alkyl complexes are known for all of the transition elements. This reaction class has been the subject of review articles. These reactions occur by a family of diverse, delicately balanced reaction pathways the dominant mechanism depends on the reaction conditions, especially the solvent. Although these pathways are now imderstood in considerable detail, the precise identities of the intermediates in some of these reaction pathways are unknown. 

In addition to migratory insertion/BHE, the aforementioned complexes are subject to further dynamical processes. Four nuclear (C/H) scrambling processes have been examined theoretically their computed activation energies agree very well with data from NMR studies [44]. 

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