Interaction of MSn (MRu, Rh, Pd) dimers with CH2 and CF2: A density functional study

Abstract

AbstractThe importance of Sn to improve the performance of noble metal‐based catalysts has been extensively discussed in the literature. However, a detailed discussion about the effect of Sn on the electronic structure of the metals has not been reported so far. In this work, density functional theory (DFT) calculations have been performed on the M2 and MSn (MRu, Rh, Pd, Sn) dimers and their interaction with CH2 and CF2 carbenes. The electronic structure, geometry, and harmonic frequencies are reported and compared with the available experimental data and to the previous published high level ab initio and DFT calculations. The calculated values of M2 are in good agreement with the experimental and theoretical results. The exception is the binding energy of the Sn dimer, which can be different from the experimental estimates as much as 16 kcal · mol−1. It has been stressed that this difficulty is related to the atomic energy reference used to estimate the binding energy. Transition metal elements are still a difficult task for DFT methods. Calculations on MSnCH2 and MSnCF2 species with different multiplicities and conformations have been performed. Bonding analyses on the MSn metal dimers showed that carbenes prefer to adsorb in bridge sites favoring a donating/backdonating mechanism of interaction that is enhanced with the presence of the Sn atom. The MSnCH2 binding energy is predicted to be 40% smaller than the MSnCF2 binding energy, following the same trends observed for the first‐row transition‐metal MCH2 and MCF2 complexes. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 95: 164–176, 2003