New Electrophilic Iridium(I) Complexes: H−H and C−H Bond Heterolysis by [(dfepe)Ir(μ-X)]2(X = O2CCF3, OTf)

Abstract

New electrophilic dimeric iridium(I) complexes [(dfepe)Ir(μ-X)]2 (dfepe = (C2F5)2PCH2CH2P(C2F5)2; X = O2CCF3, OTf) have been prepared and their reactions with H2 and cyclopentane examined. Treatment of [(cod)Ir(O2CCF3)]2 with dfepe produced an ionic product [(dfepe)Ir(cod)]+[(dfepe)Ir(O2CCF3)2]- (1), which in refluxing benzene rearranged with loss of cyclooctadiene to form [(dfepe)Ir(μ-O2CCF3)]2 (2). The corresponding reaction of [(cod)Rh(O2CCF3)]2 with dfepe yielded [(dfepe)Rh(μ-O2CCF3)]2 (3) directly. X-ray diffraction analysis of 2 revealed a hinged dimeric geometry with an unusually large interplanar angle of 82.7° defined by the two 4-coordinate metal centers (Ir(1)−Ir(2) = 4.307 A). The triflate-bridged analogue of 2 was prepared via an indirect route: addition of 1 equiv of triflic acid to (dfepe)Ir(η3-C3H5) yielded the allyl hydride complex (dfepe)Ir(η3-C3H5)(H)(OTf) (4), which eliminated propylene in refluxing heptane to quantitatively afford [(dfepe)Ir(μ-O3SCF3)]2 (5). The structure of 4 was co...