Preparation of 6,6-diarylfulvene complexes of rhodium(I) and their reaction with dioxygen

Abstract

Complexes [RhL₂]⁺[L = P(OPh)₃ or L₂= cyclo-octa-1,5-diene] react with 6,6-diarylfulvenes C₅H₄C(C₆H₄X-4)₂ to yield products [Rh{C₅H₄C(C₆H₄X-4)₂}L₂]⁺ in which the fulvene is bound to the metal through the five-membered ring. Corresponding reactions with [Rh(CO)₂]⁺ yield complexes [Rh{C₅H₄C(C₆H₄X-4)₂}₂]⁺ containing two fulvene ligands. Atmospheric oxidation of these complexes results in the linking of the exocyclic carbon atoms in the two fulvene ligands by a peroxide bridge. If the initial attack by O₂ is on the metal, the subsequent rearrangement may be viewed either as a transfer of singlet oxygen from metal to ligands or as a nucleophilic attack by peroxide on the (probably somewhat positively charged) exocyclic carbon atoms of the fulvene ligands.