Structures and hyperfine properties of ferrocene muonium adducts

The existence of multiple paramagnetic muonium adducts to ferrocene was first reported by Jayasooriya et al. in 1997, based on the presence of more than one component in the muon's spin relaxation (U.A. Jayasooriya, J.A. Stride, G.M. Aston, Appl. Magn. Reson. 13 (1997) 165.) Interpretation of the data was based on a model involving three paramagnetic species, assigned to two cycl open tadieny) ring adducts and a radical in which Mu binds directly to the metal. In this work, these species are studied by density functional methods. All three adducts are found to be stable in the staggered (antiprismatic) ring geometry, with the cyclopentadienyl adduct favored energetically by similar to 80 kJ mol(-1). No evidence is found for an agostic species of the type known for protonated ferrocenes. Computed values of A(iso) show strong method-dependence attributed to spin polarization and spin contamination effects. (c) 2005 Elsevier B.V. All rights reserved.