3. Oxidative addition from an 18-electron environment

It is possible to start from a metal with 18 electrons. There are two possible scenarios: either a doublet-bearing ligand emerges from the coordination sphere and we're back to the previous problem with, what's more, a 16-electron species that can be very reactive, or the metal is a doublet donor.

• The first case can be illustrated by the action of trichlorosilane on carbonyl iron, which first generates Fe(CO) ₄ , a 16-electron compound :

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