Using both ab initio and density functional theory (DFT) calculations in combination with basis sets of triple- and quadruple-xi quality we investigate the molecular and electronic structure of the half-sandwich eta(5)-(Cp*)C+ cation. The results indicate that the lowest-energy rotamer is a C-5-symmetric ground state singlet while the triplet state is C-s-symmetric and similar to 68 kcal/mol higher in energy. A topological analysis of the theoretical electron density based on the quantum theory of atoms in molecules (QTAIM) indicates that the eta(5)-type bonding between the apical carbon atom and Cp* comprises five bond paths each bearing a bond critical point of type (3,-1). (C) 2013 Elsevier B.V. All rights reserved.