@article{lehman_pahls_meredith_sommer_heinekey_cundari_ison_2015, title={Oxyfunctionalization with Cp*Ir-III(NHC)(Me)(CI) with O-2: Identification of a Rare Bimetallic Ir-IV mu-Oxo Intermediate}, volume={137}, ISSN={["0002-7863"]}, DOI={10.1021/ja512905t}, abstractNote={Methanol formation from [Cp*Ir(III)(NHC)Me(CD2Cl2)](+) occurs quantitatively at room temperature with air (O2) as the oxidant and ethanol as a proton source. A rare example of a diiridium bimetallic complex, [(Cp*Ir(NHC)Me)2(μ-O)][(BAr(F)4)2], 3, was isolated and shown to be an intermediate in this reaction. The electronic absorption spectrum of 3 features a broad observation at ∼660 nm, which is primarily responsible for its blue color. In addition, 3 is diamagnetic and can be characterized by NMR spectroscopy. Complex 3 was also characterized by X-ray crystallography and contains an Ir(IV)-O-Ir(IV) core in which two d(5) Ir(IV) centers are bridged by an oxo ligand. DFT and MCSCF calculations reveal several important features of the electronic structure of 3, most notably, that the μ-oxo bridge facilitates communication between the two Ir centers, and σ/π mixing yields a nonlinear arrangement of the μ-oxo core (Ir-O-Ir ∼ 150°) to facilitate oxygen atom transfer. The formation of 3 results from an Ir oxo/oxyl intermediate that may be described by two competing bonding models, which are close in energy and have formal Ir-O bond orders of 2 but differ markedly in their electronic structures. The radical traps TEMPO and 1,4-cyclohexadiene do not inhibit the formation of 3; however, methanol formation from 3 is inhibited by TEMPO. Isotope labeling studies confirmed the origin of the methyl group in the methanol product is the iridium-methyl bond in the [Cp*Ir(NHC)Me(CD2Cl2)][BAr(F)4] starting material. Isolation of the diiridium-containing product [(Cp*Ir(NHC)Cl)2][(BAr(F)4)2], 4, in high yields at the end of the reaction suggests that the Cp* and NHC ligands remain bound to the iridium and are not significantly degraded under reaction conditions.}, number={10}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Lehman, Matthew C. and Pahls, Dale R. and Meredith, Joseph M. and Sommer, Roger D. and Heinekey, D. Michael and Cundari, Thomas R. and Ison, Elon A.}, year={2015}, month={Mar}, pages={3574–3584} }
 @article{lehman_boyle_sommer_ison_2014, title={Oxyfunctionalization with Cp*Ir-III(NHC)(Me)L Complexes}, volume={33}, ISSN={["1520-6041"]}, DOI={10.1021/om5007352}, abstractNote={A series of monomethyl Cp*IrIII complexes were synthesized and studied for the formation of methanol in water. Methanol yields of 75(4)% in the presence of O2 were obtained. From isotope labeling studies, it was determined that O2 is the source of the oxygen atom in the product. From kinetic studies, oxyfunctionalization appears to proceed by dissociation of an L-type ligand followed by O2 binding and insertion.}, number={19}, journal={ORGANOMETALLICS}, publisher={American Chemical Society (ACS)}, author={Lehman, Matthew C. and Boyle, Paul D. and Sommer, Roger D. and Ison, Elon A.}, year={2014}, month={Oct}, pages={5081–5084} }
 @article{lehman_gary_boyle_sanford_ison_2013, title={Effect of Solvent and Ancillary Ligands on the Catalytic H/D Exchange Reactivity of Cp*Ir-III(L) Complexes}, volume={3}, ISSN={["2155-5435"]}, DOI={10.1021/cs400420n}, abstractNote={The reactivity of a series of Cp*IrIII(L) complexes that contain a diverse set of ancillary ligands, L, (L = PMe3, N-heterocyclic carbene, NHC = 1,3-dimethylimidazol-2-ylidene, aqua, 4-t-butylpyridine, and 4-(2,4,6-tris-(4-t-butylphenyl)pyridinium)pyridine tetrafluoroborate) has been examined in catalytic H/D exchange reactions between C6H6 and a series of deuterated solvents (methanol-d4, acetic acid-d4, and trifluoroacetic acid-d1). These studies demonstrate that (1) the mechanism of catalytic H/D exchange is significantly influenced by the nature of the solvent; (2) electron-donating ligands (PMe3, NHC) promote the formation of Ir hydrides in methanol-d4, and these are critical intermediates in catalytic H/D exchange processes; and (3) weak/poorly donating ligands (4-t-butylpyridine, 4-(2,4,6-tris-(4-t-butylphenyl)pyridinium)pyridine tetrafluoroborate and aqua) can support efficient H/D exchange catalysis in acetic acid-d4.}, number={10}, journal={ACS CATALYSIS}, author={Lehman, Matthew C. and Gary, J. Brannon and Boyle, Paul D. and Sanford, Melanie S. and Ison, Elon A.}, year={2013}, month={Oct}, pages={2304–2310} }