Carbon–fluorine bond activation in the reactions between 1,2-bis[bis(2,6-difluorophenyl)phosphino]ethane and [{MCl(µ-Cl)(η5-C5Me5)}2] (M = Rh or Ir)

Abstract

The new fluorine-containing diphosphine (C₆H₃F₂-2,6)₂PCH₂CH₂P(C₆H₃F₂-2,6)₂ I has been prepared and structurally characterized by single-crystal X-ray diffraction. The reaction between [{RhCl(µ-Cl)(η⁵-C₅Me₅)}₂] and I in refluxing benzene yielded the cationic species [RhCl{η⁵-C₅Me₃[(2-CH₂C₆H₃F-6)P(C₆H₃F₂-2,6)CH₂]₂-1,3}]⁺, which was characterized as the BF₄^– salt 1. The reaction involved the regiospecific activation of two C–F bonds and two C–H bonds and the formation of two C–C bonds. In contrast, the reaction between [{IrCl(µ-Cl)(η⁵-C₅Me₅)}₂] and I did not involve C–F bond activation, but resulted in the formation of the dinuclear complex [{IrCl₂(η⁵-C₅Me₅)[P(C₆H₃F₂-2,6)₂CH₂]}₂] 2, the characterization of which was confirmed by the synthesis of the (C₆F₅)₂PCH₂CH₂P(C₆F₅)₂ analogue [{IrCl₂(η⁵-C₅Me₅)[P(C₆F₅)₂CH₂]}₂] 3. The complexes [MCl{(C₆H₃F₂-2,6)₂PCH₂CH₂P(C₆H₃F₂-2,6)₂}(η⁵-C₅Me₅)]⁺BF₄^– (M = Rh 4 or Ir 5), unlike their (C₆F₅)₂PCH₂CH₂P(C₆F₅)₂ analogues, did not undergo C–F and C–H bond activation and C–C bond formation on thermolysis. The structures of complexes 2–4 have been determined by single-crystal X-ray diffraction.