Abstract: Metallocene compounds with two indenyl-type ligands linked in the 4 position by means of a divalent bridging group can be suitably used as components of catalysts for the polymerization of olefins. In particular, it is possible to prepare saturated or unsaturated elastomeric copolymers of ethylene characterized by valuable properties, such as low ash content and uniform distribution of the comonomers in the polymer chain.

Abstract: Disclosed are catalyst components for the polymerization of olefins which include magnesium halide in active form, and, supported thereon, a titanium halide or titanium halogen alcoholate and an electron-donor compound selected from the group diamines of formula ##STR1## wherein the radicals R.sub.1 to R.sub.10 are the same or different and are hydrogen or C.sub.1 -C.sub.18 hydrocarbon radicals, with the proviso that at least one of the R.sub.7 and R.sub.8 radicals and at least one of the R.sub.9 and R.sub.10 radicals are not hydrogen. Also, disclosed are catalysts obtained from the catalyst components and an Al-alkyl compound, as well as catalysts obtained by reaction of an Al-alkyl compound and a diamine of formula (I) with a solid catalyst component including a titanium halide or a titanium halogen alcoholate, and an electron-donor compound having particular characteristics of extractability with Al-triethyl, supported on magnesium halide in active form.

Abstract: Disclosed are solid catalyst components for the polymerization of olefins comprising a titanium halide or titanium alkoxy halide, and an electron-donor compound selected from silicon compounds of the formula ##STR1## where R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are hydrocarbyl radicals, supported on a magnesium halide in active form.Also disclosed are catalysts obtained from said catalyst components and from an Al-alkyl compound, as well as catalysts obtained by the reaction of an Al-alkyl compound and a silicon compound of the formula above with a solid catalyst component comprising a titanium halide or halogen alcoholate and an electron-donor compound having specific characteristics of extractability with Al-triethyl, supported on an active magnesium halide.

Abstract: Diethers of general formula: ##STR1## where R, R.sup.I, R.sup.II, R.sup.III, R.sup.IV and R.sup.V are the same or different and are H, C.sub.1-18 linear or branched alkyl, C.sub.5-18 cycloalkyl, C.sub.6.about. aryl, C.sub.7-18 alkylaryl or C.sub.7-18 arylalkyl radicals, provided that when R is alkyl, R.sup.I is other than H or alkyl and when R.sup.I is alkyl, R is other than H or alkyl; R.sup.VI and R.sup.VIII are the same or different and are C.sub.1-18 linear or branched alkyl, C.sub.5-18 cycloalkyl, C.sub.6-18 aryl, or C.sub.7-18 arylalkyl radicals; and two or more of R to R.sup.V may be bonded to form a cyclic structure having 5 to 18 carbon atoms.The diethers are particularly useful in the preparation of Ziegler-Natta catalysts.