Hydrogen Addition to (pincer)Ir<sup>I</sup>(CO) Complexes: The Importance of Steric and Electronic Factors
作者:Jonathan M. Goldberg、Sophia D. T. Cherry、Louise M. Guard、Werner Kaminsky、Karen I. Goldberg、D. Michael Heinekey
DOI:10.1021/acs.organomet.6b00598
日期:2016.10.24
(POCOP)Ir-I(CO) [POCOP = kappa(3)-C6H3-2,6-(OPR2)(2) for R = Bu-t, Pr-i] and (PCP)Ir-I(CO) [PCP = kappa(3)-C6H3-2,6-(CH2PR2)(2) for R = Bu-t and Pr-i] complexes can add hydrogen via two distinct pathways. When R = Bu-t, (POCOP)Ir(CO) and (PCP)Ir(CO) complexes only add hydrogen via a proton-catalyzed pathway due to steric effects, yielding trans-dihydride complexes. For R = Pr-i, both systems oxidatively add hydrogen to give cis-dihydride complexes which thermally isomerize to more thermodynamically favorable trans-dihydride species, consistent with previous reports. Proton-catalyzed hydrogen addition pathways are also observed for both Pr-i-substituted (pincer)Ir(CO) complexes. (PCP)Ir(CO) complexes add hydrogen under milder conditions than the analogous POCOP species. Intermediate hydrido-pyridine Ir(III) carbonyl complexes from the proton-catalyzed pathway have been synthesized and characterized. This is the first report of a series of complexes shown to add hydrogen via concerted oxidative addition or a proton-catalyzed pathway to the same iridium center.