Tandem Oligomerization-Hydrogenation Using Brønsted Acidic Iridium Hydride Catalysts

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.