Tuning iridium (I) PCcarbeneP frameworks for facile cooperative N2O reduction

Abstract Two electron-rich PCP ligands were synthesized featuring –C(CH 3 ) 2− and –Si(CH 3 ) 2 – functional groups linking the framework backbone. PC carbene P–Ir–Cl complexes were prepared via double C–H activation protocols and the donor strengths of the new ligands were evaluated using CO stretching frequencies of monocarbonyl cations prepared from the corresponding carbene chlorides. The new tethered systems were found to be superior donors with respect to PC carbene P pincer complexes previously reported in our group. These carbene chloride complexes reacted readily with nitrous oxide (N 2 O) to form “iridaepoxides” immune to unwanted C aryl –C anchor cleavage. Rates of oxygen atom transfer from N 2 O to a series of PC carbene P–Ir–Cl compounds were also measured using 31 P{ 1 H} NMR spectroscopy. Results suggested a direct positive correlation between ligand donicity and O-atom transfer rate for all ortho -phenylene derived systems. The sterically distinct 2,3-benzo[ b ]thiophene scaffold was found to be an outlier of this trend with a relatively high reactivity rate and ν CO .