Solvent-induced reductive elimination of pentamethylcyclopentadiene from a (pentamethylcyclopentadienyl)metal hydride

Article abstract of DOI:10.1021/om00032a031

In acetonitrile solution, Cpz.ast;Ir(PPh₃)(H)₃⁺BF₄^- smoothly undergoes elimination of pentamethylcyclopentadiene (Cp*H) to yield Ir(H)₂(PPh₃)(NCMe)₃⁺BF ₄^- as the only Ir-containing product (δH^? = 69.0 ± 2.1 kJ/mol, ΔS^? = -82.0 ± 7.6 J/(K·mol), k(20°C) = 1.6 × 10^-4 s^-1). The elimination of Cp*H did not take place in neat dichloromethane. The rate law exhibited a mixed first- and second-order dependence on the acetonitrile concentration, in accord with a mechanism involving successive acetonitrile-mediated η⁵ to η³ to η¹ ring slippage reactions, the first of which is reversible.