Dehydrogenation of aliphatic polyolefins catalyzed by pincer-ligated iridium complexes.

We report the first example of the catalytic dehydrogenation of aliphatic polyolefins to give partially unsaturated hydrocarbon polymers.

Mechanism of alkane transfer-dehydrogenation catalyzed by a pincer-ligated iridium complex.

The mechanism of (PCP)Ir-catalyzed transfer-dehydrogenation has been elucidated for the prototypical substrate/acceptor couple, COA/TBE, at 55 degrees C (COA = cyclooctane; TBE = tert-butylethylene). The catalytic cycle may be viewed as the sum of two reactions: (i) hydrogenation of TBE by (PCP)IrH2 and C-H addition of a second mole of TBE to give (PCP)IrH(tert-butylvinyl), and (ii) dehydrogenation of COA by (PCP)IrH(tert-butylvinyl) to give (PCP)IrH2, COE, and TBE. These two stoichiometric reactions have been observed independently and their kinetics determined.