Mechanism of Hydrogenolysis of an Iridium-Methyl Bond: Evidence for a Methane Complex Intermediate

作者：Campos Jesus; Kundu Sabuj; Pahls Dale R; Brookhart Maurice^*; Carmona Ernesto; Cundari Thomas R

来源：Journal of the American Chemical Society, 2013, 135(4): 1217-1220.

DOI：10.1021/ja310982v

Evidence for key a-complex intermediates in the hydrogenolysis of the iridium methyl bond of (PONOP)Ir(H)(Me)(+) (1) [PONOP = 2,6-bis(di-tert-butylphosphinito)pyridine] has been obtained. The initially formed eta(2)-H-2 complex, 2, was directly observed upon treatment of 1 with H-2, and evidence for reversible formation of a a-methane complex, 5, was obtained through deuterium scrambling from eta(2)-D-2 in 2-d(2) into the methyl group of 2 prior to methane loss. This sequence of reactions was modeled by density functional theory calculations. The transition state for formation of 5 from 2 showed significant shortening of the Ir-H bond for the hydrogen being transferred; no true Ir(V) trihydride intermediate could be located. Barriers to methane loss from 2 were compared to those of 1 and the six-coordinate species (PONOP)Ir(H)(Me)(CO)(+) and (PONOP)Ir(H)(Me)(Cl).

• 出版日期2013-1-30