Catalysts

A solid particulate catalyst free from an external carrier comprising: (i) a complex of formula (I): wherein M is zirconium or hafnium; each X is a sigma ligand; L is a divalent bridge selected from -R′2C-, -R′2C-CR′2-, -R′2Si-, -R′2Si-SiR′2-, -R′2Ge-, wherein each R′ is independently a hydrogen atom, C1-C20-alkyl, tri(C1-C20-alkyl)silyl, C6-C20-aryl, C7-C20-arylalkyl or C7-C20-alkylaryl; each R1 independently is hydrogen or a linear or branched C1-C20 hydrocarbyl radical optionally containing one or more heteroatoms from groups 14-16 of the Periodic Table of the Elements; each R2 and R3 taken together form a 4-7 membered ring condensed to the benzene ring of the indenyl moiety, said ring optionally containing heteroatoms from groups 14-16, each atom forming said ring being optionally substituted with at least one R18 radical; each R18 is the same or different and may be a C1-C20 hydrocarbyl radical optionally containing one or more heteroatoms belonging to groups 14-16; each R4 is a hydrogen atom or a C1-6-hydrocarbyl radical optionally containing one or more heteroatoms belonging to groups 14-16; each W is independently a 5 or 6 membered aryl or heteroaryl ring wherein each atom of said ring is optionally substituted with an R5 group; each R5 is the same of different and is a C1-C20 hydrocarbyl radical optionally containing one or more heteroatoms belonging to groups 14-16; and optionally two adjacent R5 groups taken together can form a further mono or multicyclic ring condensed to W optionally substituted by one or two groups R5; and (ii) a cocatalyst comprising an organometallic compound of a Group 13 metal, preferably aluminoxane.