A solid particulate catalyst free from an external carrier comprising: (i) a complex of formula: wherein M is zirconium or hafnium; each X is a sigma ligand; L is a divalent bridge selected from -R' 2 C-, -R' 2 C-CR' 2 -, -R' 2 Si-, -R' 2 Si-SiR' 2 -, -R' 2 Ge-, 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 R 1 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 R 2 and R 3 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 R 18 radical; each R 18 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 R 4 is a hydrogen atom or a C 1-6 -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 R 5 group; each R 5 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 R 5 groups taken together can form a further mono or multicyclic ring condensed to W optionally substituted by one or two groups R 5; and (ii) a cocatalyst comprising an organometallic compound of a Group 13 metal, preferably aluminoxane. (i) a complex of formula: wherein M is zirconium or hafnium; each X is a sigma ligand; L is a divalent bridge selected from -R' 2 C-, -R' 2 C-CR' 2 -, -R' 2 Si-, -R' 2 Si-SiR' 2 -, -R' 2 Ge-, 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 R 1 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 R 2 and R 3 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 R 18 radical; each R 18 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 R 4 is a hydrogen atom or a C 1-6 -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 R 5 group; each R 5 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 R 5 groups taken together can form a further mono or multicyclic ring condensed to W optionally substituted by one or two groups R 5; and (ii) a cocatalyst comprising an organometallic compound of a Group 13 metal, preferably aluminoxane. M is zirconium or hafnium; each X is a sigma ligand; L is a divalent bridge selected from -R' 2 C-, -R' 2 C-CR' 2 -, -R' 2 Si-, -R' 2 Si-SiR' 2 -, -R' 2 Ge-, 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 R 1 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 R 2 and R 3 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 R 18 radical; each R 18 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 R 4 is a hydrogen atom or a C 1-6 -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 R 5 group; each R 5 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 R 5 groups taken together can form a further mono or multicyclic ring condensed to W optionally substituted by one or two groups R 5; and (ii) a cocatalyst comprising an organometallic compound of a Group 13 metal, preferably aluminoxane.