Mechanistic and reactivity studies of cationic iridium(III) complexes

A mechanistic study of the stoichiometric and catalytic H/D exchange reactions involving cationic iridium complexes is presented. Strong evidence suggests that both stoichiometric and catalytic reactions proceed via a monohydrido-iridium species. Stoichiometric deuterium incorporation reactions introduce multiple deuterium atoms into the organic products when aryliridium compounds Cp*PMe- 3Ir(C6H4X)(OTf) (X = H, o-CH 3, m-CH3, p-CH3) react with D2. Multiple deuteration occurs at the unhindered positions (para and meta) of toluene, when X = CH 3. The multiple deuteration pathway is suppressed in the presence of an excess of the coordinating ligand, CH3CN.; A detailed mechanistic study of arene C-H bond activation by Cp*(L)Ir(Me)(X) [L = PMe3, P(OMe)3; X = OTf, (CH2Cl 2)BArf-; (BArf- = B(3,5-C6H3(CF3)2) 4)-] in CH2Cl2 solution provides insight into reaction features that affect the rate of the reaction. Triflate dissociation in Cp*(L)Ir(Me)(OTf), to generate tight and/or solvent-separated ion pairs containing a cationic iridium complex, precedes C-H bond activation. Consistent with the ion-pair hypothesis, the rate of arene activation by Cp*(L)Ir(Me)(OTf) is unaffected by added external triflate salts, but shows a strong dependence on the medium.; The iridium(III) complex [Cp*(PMe3)Ir(CH3)(ClCH 2Cl)][BArf] (1) formally activates the C-H and C-F bonds of CH3F and CH3CH2F to yield ethylene complexes [Cp*(PMe3)Ir(C2H4)H][BArf] ( 2-BArf) and [Cp*(PMe3)Ir(CH3)(C 2H4)][BArf] (5), respectively. Intractable products result from the reaction of 1 and highly fluorinated substrates, possibly due to the electron withdrawing character of the fluorine atoms and/or the generation of HF.; A large kinetic isotope effect suggested that C-H bond activation is part of the rate-determining step for the reaction of Cp*(PMe3)Ir(CH 3)OTf (1) and cyclopropane to form the pi-allyl complex [Cp*(PMe3)Ir(eta3-C3H5)][OTf] (2). While studying the formation of 2, new modes of reactivity were found between iridium complexes and substituted cyclopropanes. Treatment of 1 with amino-substituted cyclopropanes resulted in the loss of methane and cyclopropyl ring-opening to form pi-allyl complexes [Cp*(PMe3)Ir(eta3-C3H4(NR 1R2))][OTf] (R1 = R2 = Bn; R1 = Bn, R2 = Ph). In contrast, treatment of 1 with alkoxy-substituted cyclopropanes resulted in the elimination of alcohol and migration of the iridium methyl group to the cyclopropyl fragment to form a different type of allyl complex, [Cp*(PMe3)Ir(eta 3-C3H4(CH3))][OTf]. (Abstract shortened by UMI.)...