Reactivity of co-ordinated ligands. Part XIV. The reactions of some cyclo-octa-1,3,5-triene complexes of cobalt(I), rhodium(I), and iridium(I)

Abstract

The cyclo-octa-1,3,5-triene (cotr) complexes [(cotr)MCl]₂, (cotr)M(π-cp) and (cotr)M(acac)(M = Rh^I or Ir^I) have been prepared and some of their reactions examined. Protonation of cotrM-(π-cp)(M = Co^I, Rh^I, or Ir^I) readily leads to cations of the type [(C₈H₁₁)M(π-cp)]⁺. The C₈H₁₁⁺ entity adopts a variety of bonding modes and interconversion between these various modes readily occurs. Kinetics of such interconversions for both the Rh^I and Ir^I cations have been followed by the change in their ¹H n.m.r. spectra with time. Possible mechanisms are discussed. Nucleophilic addition to these cations gives the expected neutral complexes of formula (C₈H₁₁Y)M(π-cp), the nature of these products depending on the reaction temperature employed. The rhodium complex, (C₈H₁₀)Rh(π-cp), does not react cleanly with any of the other electrophiles tried (AcCl–AlCl₃ or DMF–POCl₃).