Supporting Information for Geometry optimisation of a Ru(IV) allyl dicationic complex: a DFT failure? Maria José Calhorda, a Paul S. Pregosin, b Luis F. Veiros c, * a Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, 1749- 016 Lisboa, Portugal. b Laboratory of Inorganic Chemistry, ETHZ, Hönggerberg CH-8093 Zürich, Switzerland. c Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Av. Rovisco Pais 1, 1049- 001 Lisboa, Portugal. Methods and basis sets The methods and basis sets used are described in Computation Details (Section 2) along with the corresponding references. The key for the basis set labelling is presented in Table S1, below, and the methods are labelled with the usual acronyms. Table S1 Key for the basis set labelling Ru C, H and N I L – 4-31G(d) I M – LanL2DZ plus f-polarization II L – 4-31G(d) plus diffuse functions on the allylic carbons II M – SDD plus f-polarization III L – 6-311G(d,p) III M – 3-21G plus f-polarization IV L – TZVP V L – cc-pVTZ VI L – cc-pVQZ