ELECTRONIC-STRUCTURE AND PROPERTIES OF TRANSITION-METAL COMPLEXES MCH2 AND M5CH2 (M=FE,NI,CU) BY DENSITY-FUNCTIONAL METHODS

The electronic structure and properties of carbenes MCH2 and M5CH2 (M = Fer Ni, Cu) were studied using density functional methods (DF), part icularly the local density approach (LDA) with the non-local correctio ns (NL) of Becke and Perdew and the ADF program of Bearends and collea gues. In the first part of this report the equilibrium geometries and dissociation energies for the process MCH2 --> M + CH2 at the ground s tate of the compound MCH2 were calculated. Charge distributions by pop ulation analysis, dipole moments and vibrational frequencies were also evaluated. All the calculations were done using the triple-zeta basis set with frozen core orbitals and the NL corrections. Comparisons bet ween our results and other calculations using ab initio methods and ex perimental values were carried out. Calculations were done for the gro und doublet state of CuCH2, the singlet state of NiCH2 and the triplet state of FeCH2, In order to compare our results with some references found in the literature we have included in our study two states of th e cation FeCH2+, In the second part of this report, doublet states for Cu5CH2 and singlet states for Ni5CH2 were studied, considering planar and non-planar models for the M-5 clusters and two positions (paralle l and diagonal) for the CH2 group. The tripler state for Fe5CH2 was st udied with the non-planar model for the Fe-5 cluster. Optimization of the position of the CH2 group in the cluster, dissociation energies, d istribution of charges in the molecule and dipolar moments were also c alculated and comparisons were made with the MCH2 results. (C) 1997 El sevier Science B.V.