Question

Predict the product (C) of the following equilibrium:

[(η⁵-Cp)Ir(CH₂CH₃)(PMe₃)(OEt₂)]⁺   ↔ C + OEt₂              (C obeys the 18e- rule)

Answer 1

[(η⁵-Cp)Ir(CH₂CH₃)(PMe₃)(OEt₂)]⁺   ↔[(η⁵-Cp)Ir(CH₂ = CH₂)(PMe₃)] + OEt₂ + H⁺

The complex C is shown above and this is 18e^- complex. The ethyl group in the left side will lose one proton from the β-hydrogen (-CH3) group forming π-complex between metal and the ethylene by a process known as β-hydrogen elimination; which is a 2e^- donor with no formal charge. The electron count is shown below in neutral atom electron count method.

(η⁵-Cp)…………>5e-

Ir………………..>9e-

(CH₂ = CH₂)………>2e-

(PMe₃)……………>2e-

Total electron……..> 18e-