Scalar Relativistic Study of the Structure of Rhodium Acetate

Rhodium acetate, related rhodium carboxylates, and rhodium amide complexes are powerful catalysts for carbene chemistry. They readily promote the decomposition of diazo compounds and transfer the resulting carbene to a variety of substrates. There have been several quantum chemistry studies of these compounds, particularly of the acetate. These have all used non-relativistic methods, and all have shown optimized Rh-Rh bond lengths significantly longer than the experimental value. In this study we have surveyed several scalar relativistic DFT methods using Gaussian, Slater, and numerical basis functions (in DGAUSS, ADF, and DMOL3). Several combinations of exchange-correlation functionals with relativistic and non-relativistic effective core potentials (ECP) were investigated, as were non-relativistic and all electron scalar relativistic methods. The combination of the PW91 exchange and PW91 correlation functional with the ChristiansenErmler ECP gave the best results: 2.3918 Å compared to the experimental value of 2.3855±0.0005 Å.