A metallocene compound of formula (I): wherein M is zirconium, titanium and hafnium; X is a hydrogen atom, a halogen atom or a hydrocarbon radical; R1 is a linear C¿1?-C20-alkyl radical; R?2¿ is a hydrogen atom or hydrocarbon R?3, R4, R5, R6, R7, and R8¿, are hydrogen atoms or hydrocarbon radicals, A is a sulphur (S) atom or an oxygen (O) atom; Q is a radical of formula (II), (III) or (IV) being bonded to the indenyl at the position indicated by the symbol *; (II), (III), (IV) wherein T1 is a sulphur atom, an oxygen (O) atom or a NR; R?9, R10 and R11¿ are hydrogen atoms or hydrocarbon radicals; T?2, T3, T4, T5, and T6¿ are carbon atoms (C) or nitrogen atoms (N); m?1, m2, m3, m4 and m5¿ are 0 or 1; R?12, R13, R14, R15 and R16¿ are hydrogen atoms or hydrocarbon radicals with the provisos that at least one of R?12, R13, R14, R15 and R16¿ is different from hydrogen atoms, and that no more than two of T?2, T3, T4, T5 and T6¿ are nitrogen atoms.