Electrophilic attack on coordinated

Electrophilic attack on coordinated cyclopentadienyl rings, particularly those in ferrocene, is well established. This process occurs in a similar fashion to electrophilic attack on arenes and was used to establish the binding mode of the Cp ligand in ferrocene (see Equation 3.88). These reactions of the Cp ligand with electrophiles are described in more detail in Chapter 12, which covers electrophilic attack on coordinated ligands. Friedel-Crafts acylation, formylation, aminomethylation, and mercuration are all known. - ... 

Electrophilic attack on coordinated polyenyl ligands is uncommon, but electrophilic attack on the Ti -cyclopentadienyl ligands in certain complexes has become synthetically valuable. For example, the acetylation of ferrocene (Equation 12.75) is a reliable Friedel-Crafts process " and generates derivatives used to make many ferrocenyl ligands. Similar electrophilic aromatic substitution reactions of haloboranes on ferrocene (shown in Equation 12.76) and on the anion generated from deprotonation of tungstenocene dihydride (Equation 12.77) leads to borylcyclopentadienyl complexes. " ... 

B. Electrophilic Attack on Coordinated Double Bond Systems... 

C-C bond formation resulting from electrophilic attack on coordinated double-bond systems is a useful synthetic reaction (Section lll,B). The formation of C-X bonds by electrophilic attack of X, however, is restricted essentially to or D. Electrophiles such as Br or NOj usually lead to oxidative cleavage of the metal-olefin complex, although NBS (iV-bromosuccinimide) has been reported to act as a hydride acceptor in some cases (Khand et al., 1968, 1969). 

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