NEW ELECTROPHILIC IRIDIUM(I) COMPLEXES - H-H AND C-H BOND HETEROLYSISBY [(DFEPE)IR(MU-X)](2) (X=O2CCF3, OTF)

New electrophilic dimeric iridium(I) complexes [(dfepe)Ir(mu-X)](2) (d fepe = (C2F5)(2)PCH2CH2P(C2F5)(2); X = O2CCF3, OTf) have been prepared and their reactions with H-2 and cyclopentane examined. Treatment of [(cod)Ir(O2CCF3)](2) with dfepe produced an ionic product [(dfepe)Ir(c od)](+)[(dfepe)Ir(O2CCF3)(2)](-) (1), which in refluxing benzene rearr anged with loss of cyclooctadiene to form [(dfepe)Ir(mu-O2CCF3)](2) (2 ). The corresponding reaction of [(cod)Rh(O2CCF3)](2) with dfepe yield ed [(dfepe)Rh(mu-O2CCF3)](2) (3) directly. X-ray diffraction analysis of 2 revealed a hinged dimeric geometry with an unusually large interp lanar angle of 82.7 degrees defined by the two 4-coordinate metal cent ers (Ir(1)-Ir(2) = 4.307 Angstrom). The triflate-bridged analogue of 2 was prepared via an indirect route: addition of 1 equiv of triflic ac id to (dfepe)Ir(eta(3)-C3H5) yielded the allyl hydride complex (dfepe) Ir(eta(3)-C3H5)(H)(OTf) (4), which eliminated propylene in refluxing h eptane to quantitatively afford [(dfepe)Ir(mu-O3SCF3)](2) (5). The str ucture of 4 was confirmed by X-ray diffraction. In contrast to [(dfepe )Ir(mu-Cl)](2), the acetate- and triflate-bridged analogues 2 and 5 ar e reactive toward both H-2 and alkane C-H bonds. Treatment of 2 with H -2 (20 degrees C) or cyclopentane (150 degrees C) cleanly afforded (df epe)(2)Ir-2(mu-H)(2)(H)(mu-O2CCF3) (6) and CpIr(dfepe), respectively. Surprisingly, the corresponding reactions of 5 are significantly slowe r, suggesting that the concomitant release of the stronger acid CF3SO3 H may inhibit these heterolysis reactions.