Ligand Field Model and d-d Spectra of dN Metallocene Complexes

Abstract

Complete ligand field calculations, including spin-orbit coupling, have been carried out for bent d1 metallocene complexes, [M(Cp)2Ln] (Cp = η5-cyclopentadienyl, n = 1 or 2), in C2v symmetry. Using the strong-field coupling formalism (with exclusion of spin-orbit coupling) the full energy matrices for d2, d3, and d4 bent metallocenes were constructed in terms of four ligand field splitting parameters and two Racah interelectronic repulsion parameters (only d2 energy matrices are presented here). The bonding in the bent d1 C2v M(Cp)2 fragment was analyzed from the point of view of the ligand field model. The experimental d-d transition energies of two d1 metallocene dichlorides, vanadocene and niobocene dichlorides, have been assigned, the values of four one-electron ligand field splitting parameters determined and the effect of spin-orbit coupling estimated. The ground state of both d1 metallocene dichlorides has shown to be 2A(111), the d-orbital energy order being 1a1 < b1 < b2 < 2a1 < a2. Finally, the prediction of d-d spectra for d2, d3, and d4 bent metallocene complexes is presented.