Synthesis, Characterization, and Dehydrogenation Activity of an Iridium Arsenic Based Pincer Catalyst

• Published in: Organometallics Vol. 33; no. 19; pp. 5198 - 5202
• Main Authors: Brayton, Daniel F, Beaumont, Paul R, Fukushima, Erin Y, Sartain, Hope T, Morales-Morales, David, Jensen, Craig M
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 13.10.2014; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Inorganic & Nuclear; Chemistry, Organic; Physical Sciences; Science & Technology; LIGAND; SELECTIVE DEHYDROGENATION; COMPLEXES; ALKANES
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om5005034

A new arsenic-based pincer (AsOCOAs) dehydrogenation catalyst has been synthesized, IrHCl{2,6-C6H3-(O-AsBut 2)} (3). Treatment with an equivalent of base (NaO-tert-butoxide) under an atmosphere of hydrogen gas affords the dihydride catalyst IrH2{2,6-C6H3-(O-AsBut 2)} (4). The activity of 3 was explored under transfer dehydrogenation conditions with cyclooctane and tert-butyl ethylene, giving a maximum turnover number of 960 at 175 °C in 24 h. Acceptorless dehydrogenations were also explored with pyrrolidine-based molecules, ethylperhydrocarbazole (5), methylperhydroindole (6), and butylpyrrolidine (7), in which all results indicate 3 is roughly half as active as the analogous phosphine-based pincer catalyst 2. Akin to the phosphine pincer catalysts the activity was seen to steadily improve with increasing temperature, peaking at 175 °C, upon which thermal decomposition sets in.