Hydrogen intramolecular heterolytic activation

The mechanism for cyclometallation was proposed to involve a concerted heterolytic process with hydrogen atom abstraction and metallacycle formation occurring in a four-center transition state. Kinetic and labeUng studies in the cyclometallation reactions indicate that intramolecular y-C-H activation is the rate-limiting step [290]. 

Several inter- and intramolecular combinations of bulky Lewis acid-base pairs were effectively probed for the heterolytic cleavage of hydrogen. Highly active FLPs of Figure 15.2 (B, C) with a linked design were reported from the groups of Erker, Repo, Rieger, and Tamm [15]. 

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