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)

The new fluorine-containing diphosphine (C6H3F2-2,6)(2)PCH2CH2P(C6H3F2-2,6)(2) I has been prepared and structurally characterized by single-crystal X-ray diffraction. The reaction between [{RhCl(mu-Cl)(eta(5)-C5Me5)}(2)] and I in refluxing benzene yielded the cationic species [RhCl{eta(5)-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(mu-Cl)(eta(5)-C5Me5)}(2)] and I did not involve C-F bond activation, but resulted in the formation of the dinuclear complex [{IrCl2(eta(5)-C5Me5)[P(C6H3F2-2,6)(2)CH2]}(2)] 2, the characterization of which was confirmed by the synthesis of the (C6F5)(2)PCH2CH2P(C6F5)(2) analogue [{IrCl2(eta(5)-C5Me5)[P(C6F5)(2)CH2]}(2)] 3. The complexes [MCl{(C6H3F2-2,6)(2)PCH2CH2P(C6H3F2-2,6)(2)}(eta(5)-C5Me5)]+BF4- (M = Rh 4 or Ir 5), unlike their (C6F5)(2)PCH2CH2P(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.