Abstract: A multistage process comprising the step of polymerizing propylene in the presence the presence of a catalysts system, comprising one or more metallocene compound of formula (I): wherein M is an atom of a transition metal; p is an integer from 0 to 3, X, same or different, is a hydrogen atom, a halogen atom, or a hydrocarbon group; L is a divalent bridging R1 and R2, are C1-C20-alkyl radicals; T, equal to or different from each other, is a moiety of formula (IIb) or (IIa): wherein R3, R4, R5, R6, R7, R3?, R4?, R5?, R6? and R7?, are hydrogen atoms or hydrocarbon groups; with the proviso that at least one among R3, R4, R5, R6, R7 is different from hydrogen; R11 is a hydrogen atom or a hydrocarbon group; R8, R9 and R10, are hydrogen atoms or hydrocarbon groups; and further comprising the step of contacting, under polymerization conditions, in a gas phase, ethylene and one or more comonomers.

Abstract: Ethylene based polymers having high molecular weights can be obtained in high yields at temperatures of industrial interest, by carrying out the polymerization reaction in the presence of catalysts comprising single carbon bridged metallocenes, which has a particular ligand system containing a heteroatom.