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Published September 28, 2009 | Supplemental Material
Journal Article Open

Heterolytic Benzene C−H Activation by a Cyclometalated Iridium(III) Dihydroxo Pyridyl Complex: Synthesis, Hydrogen−Deuterium Exchange, and Density Functional Study

Abstract

We report the synthesis of the pincer-cyclometalated (NNC^(t-Bu))Ir(III) dihydroxo pyridyl complex 6, which catalyzes hydrogen−deuterium (H/D) exchange between water and benzene in the presence of base (TOF = ~6 × 10^(−3) s^(−1) at 190 °C). Experimental and density functional theory (B3LYP) studies suggest that H/D exchange occurs through loss of pyridine followed by benzene coordination and C−H bond activation by a heterolytic substitution mechanism to give a phenyl aquo complex, which may dimerize. Exchange of H_2O for D_2O followed by the microscopic reverse of CH activation leads to deuterium incorporation into benzene. Synthesis of the μ-hydroxo phenyl dinuclear complex [(NNC^(t-Bu))Ir(Ph)(μ-OH)]_2 (9) also catalyzes H/D exchange with a turnover frequency (TOF = ~7 × 10^(−3) s^(−1) at 190 °C) similar to that for 6.

Additional Information

Copyright © 2009 American Chemical Society. Received January 17, 2009. Publication Date (Web): September 2, 2009. We thank the National Science Foundation (Grant No. CHE-0328121), Chevron Texaco Energy Technology Co., and Scripps Florida for financial support of this research. We thank Mr. Timothy Stewart and Prof. Robert Bau for X-ray structure determination. Supporting Information: A CIF file and tables and figures giving X-ray structural data for 9, 1H NMR spectra for the stability studies of 6 in D2O with and without added KOD, a plot of turnover number vs time for H/D exchange using 6 as a catalyst, a 1/[Py] plot for H/D exchange with 6, 1H NMR spectra for compounds 2−6 and 9−11, and B3LYP xyz coordinates of transition states. This material is available free of charge via the Internet at http://pubs.acs.org.

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