A
solid, particulate catalyst 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 a linear or branched C1-C20 hydrocarbyl radical optionally containing one or more heteroatoms from groups 14-16; T1 and T4, which can be the same or different, are an OR<2>, a SR<2>, CH(R<18>)2, CH2R<18>,
aryl or heteroaryl group; each R<2>, which can be the same or different, is a C1-C20 hydrocarbyl radical; each R<18>, which can be the same or different, is a C1-C20 hydrocarbyl radical or two R<18> groups together with the
carbon atom to which they are attached may form a cyclic C4-C20 hydrocarbyl group; T2 and T3, which may be the same or different, are a C(R<18>)3 group; W1 and W2, which may be the same or different, are 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>, which can be the same or different, 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 W1 or W2, optionally substituted by one or two groups R5; and (ii) a cocatalyst.