Zhou M.,Rutgers New Brunswick |
Johnson S.I.,California Institute of Technology |
Gao Y.,Rutgers New Brunswick |
Emge T.J.,Rutgers New Brunswick |
And 3 more authors.
Organometallics | Year: 2015
A pincer iridium(III) complex, (Phebox)Ir(OAc)2OH2 (1) (Phebox = 3,5-dimethylphenyl-2,6-bis(oxazolinyl)), selectively cleaves the benzylic C-H bond of mesitylene to form an isolable iridium mesityl complex, (Phebox)Ir(mesityl)(OAc) (3), in >90% yield. The trifluoroacetate analogue, (Phebox)Ir(OCOCF3)2OH2 (2), was synthesized to compare with complex 1 for C-H activation, and (Phebox)Ir(mesityl)(OCOCF3) (4) was synthesized by ligand exchange of complex 3. Both complexes 1 and 2 catalyze H/D exchange between mesitylene and D2O at 180 °C, exclusively at the benzylic position; 2 gave a higher turnover number (11 TO) than 1 (6 TO) in 12 h. Using d4-acetic acid as the source of deuterium, up to 92 turnovers of benzylic H/D exchange of mesitylene were obtained with complex 1. (Phebox)Ir(OCOCF3)2OH2 catalyzed the benzylic C-H oxidation of mesitylene using Ag2O as a terminal oxidant at 130 C, to form 3,5-dimethylbenzaldehyde and 3,5-dimethylbenzoic acid in 35% ± 4% yield (5.1 ± 0.6 TO). DFT calculations were used to investigate two possible pathways for the catalytic oxidation of mesitylene: (1) C-H activation followed by oxy-functionalization and (2) Ir-oxo formation followed by outer-sphere C-H hydroxylation. Results of calculations of the C-H activation pathway appear to be the more consistent with the experimental observations. (Chemical Equation Presented). © 2015 American Chemical Society.
Krungleviciute V.,Southern Illinois University Carbondale |
Pramanik S.,Rutgers New Brunswick |
Migone A.D.,Southern Illinois University Carbondale |
Li J.,Rutgers New Brunswick
Microporous and Mesoporous Materials | Year: 2012
Zn(bdc)(ted) 0.5 is a metal-organic framework with a 3D porous structure containing intersecting channels with two different size windows. Methane adsorption isotherms were measured on this MOF at several temperatures between 88 and 103 K. Unlike all other previous studies conducted on this sorbent, we observed two very distinct substeps in the isotherms, while only one such feature is reported in other studies. Possible scenarios for explaining the origin of these newly observed features are proposed. We studied the kinetics of adsorption of methane on this sorbent for isotherms measured at four temperatures. These measurements provided us with information of how equilibrium is approached as gas was added to the sorbent. We have also calculated the pore volume and the effective specific surface area for this material and have obtained the isosteric heat values for methane on this sorbent from the adsorption data. © 2012 Elsevier Inc. All rights reserved.