Accurate Prediction of Ir-H Bond Dissociation Enthalpies by Density Functional Theory Methods

The iridium hydride complexes have been extensively used in organic reactions,such as oxidation and hydro-genation reactions.In many of these reactions,the dissociation or formation of Ir-H bond plays an important role in determining the overall reaction rates and yields.In the present study,the accuracy of different theoretical meth-ods for prediction of Ir-H bond strengths has been examined on the basis of the previously reported Ir-H BDEs of 17 different complexes.Comparing the performance of different DFT functionals(e.g.B3LYP,TPSS,M06),different basis sets(including the different effective core potentials(ECP)on Ir and I atoms,and the total electron basis sets on the other atoms),and different solvation models(SMD,CPCM,and IEFPCM)in solution phase single point calculations,we found that the gas-phase calculation with TPSS/(LanL2DZ:6-31G(d))method is relatively more accurate than the other gas-phase calculation methods,and can well simulate the Ir-H BDEs in low-polarity solvents(such as chlorobenzene and dichloroethane).Finally,efforts were put in analyzing the structure-activity re-lationships between the ligand structure(around Ir center)and the Ir-H BDEs.We wish the present study could benefit future studies on the Ir-H complexes involved organic reactions.

Accurate Prediction of Au--P Bond Strengths by Density Functional Theory Methodst

The recent development of Au-catalyzed reactions has greatly enriched the methods of organic synthesis. The phosphine or phosphate-coordinated Au complexes have shown high efficiency in catalyzing various C--C and C-- H activations. In many of these reactions, the Au--P bond strength was found to play an important role in deter- mining the catalytic efficiency. In the present study, the accuracy of different theoretical methods for prediction of Au--P strengths has been examined on basis of the experimental enthalpy changes between different CIAu（PR3） and C1Au（THT） （THT----tetrahydrothiophene）. By comparing the different DFT functionals （e.g. B3LYP, TPSS, M06）, different basis sets （including the different effective core potentials on Au and the total electron basis sets on all other atoms）, and different solution phase single point calculations, we found that the TPSS/（CPE-121G＋f： 6-311 ＋G（d,p）（SMD）//TPSS/（CPE-121G：6-31G（d） （M1） method gives the best correlations with the available experimental results. Meanwhile, the calculations with B3LYP//TPSS and MOS//TPSS also give comparable calculation results. Finally, the specified method （M1） is used to calculate the Au--P bond dissociation enthalpies and energies of different C1Au（PR3）/CIAu（P（OR）3） complexes. By accurately reproducing the available experimental results, we believe that the method （M1） is reliable for the theoretical analysis of Au-P systems.