(PONOP)-P-R4-Ir-Me ((R)1) and (POCOP)-P-R4-Ir-CO ((R)2), R = Bu-t or Pr-i, are known to undergo acid-catalyzed oxidative addition of H-2 that yields octahedral products with two hydrides in a trans-configuration. We use density functional theory to study the free energies (Delta G(trans)) and equilibrium isotope effects (EIEtrans) for H-2/D-2 addition to (R)1, (R)2, and related complexes for R = Bu-t, Pr-i, and Me. For a given R, reaction of (R)1 is similar to 5 kcal/mol more exergonic than (R)2. For a given subclass of complexes, Delta G(trans) is more exergonic for the smaller R. The computed values of Delta G(trans) vary between +5.1 and -17.4 kcal/mol. EIEtrans varies between 0.78 and 1.22. Counterintuitively, it is the less-exergonic reactions that afford products with shorter Ir-H bonds, greater symmetric and asymmetric trans-Ir-(H)(2) stretching vibrational frequencies, and more inverse EIEtrans This disparity is amplified in (PONOP)-P-Me4-Os-CO, where Delta G(trans) is -35.2 kcal/mol, yet the Os-H bonds are long, and the Os-H vibrational frequencies are low as compared with the Ir-H bonds, and EIEtrans is high (1.20). Attempts are made to account for the inverted bond strength-bond length correlation based on the hydricity of the products and the total negative charge on the trans-Ir(H)(2) unit as computed using the Quantum Theory of Atoms in Molecules.