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Tandem Oligomerization-Hydrogenation Using Brønsted Acidic Iridium Hydride Catalysts
Austin J Leitgeb1, Scott M Chapp1, Caleb D Fast1
1Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, United States.
None:
Cationic iridium complexes bearing the tris-[3,5-bis-(trifluoromethyl)-phenyl]-phosphine ligand unexpectedly give acidic metal hydrides. Net-dihydrogen heterolysis at such complexes provides hydrogenation catalysis by an ionic mechanism. The direct reduction of isobutene competes with cationic oligomerization to give the gasoline additive isooctane (2,4,4-trimethylpentane) as a major product of a tandem oligomerization/hydrogenation sequence. Mechanistic experiments argue for the role of neutral iridium hydrides generated by the proton transfer of a cationic hydride precursor to an olefin substrate.
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