Scalar-relativistic density functional and ab initio pseudopotential studyof zero-valent d and f metal bis-eta(6)-benzene sandwich complexes M(C6H6)(2) (M = Sc, Ti, Y, Zr, La, Lu, Hf, Th, U)

The electronic and molecular structures of selected zero-valent d and f met al bis-eta(6)-benzene sandwich complexes M(C6H6)(2) (M = Sc, Ti, YI Zr, La, Lu, Hf,Th,U) were investigated at the scalar-relativistic level with an al l-electron density functional method (DET) using the zero-order regular app roximation Hamiltonian (ZORA) and with energy-consistent ab initio pseudopo tentials (PP) at the coupled-cluster level [CCSD(T)]. The results obtained with both methods consistently support the earlier conclusion about the the rmochemical stability of Th and U bis-eta(6)-benzene sandwich complexes and their derivatives. A comparison of energetic and geometric parameters demo nstrates that the ZORA DFT approach is a promising alternative tool to, e.g ., PP CCSD(T) for investigating theoretically the organometallic chemistry of d and f elements. (C) 2000 John Wiley & Sons, Inc.