H Addition to Pincer Iridium Complexes Yielding trans-Dihydride Products: Unexpected Correlations of Bond Strength with Bond Length and Vibrational Frequencies.

PONOP-Ir-Me (1) and POCOP-Ir-CO (2), R = Bu or Pr, are known to undergo acid-catalyzed oxidative addition of H that yields octahedral products with two hydrides in a trans-configuration. We use density functional theory to study the free energies (Δ G) and equilibrium isotope effects (EIE) for H/D addition to 1, 2, and related complexes for R = Bu, Pr, and Me. For a given R, reaction of 1 is ∼5 kcal/mol more exergonic than 2.