Components and catalysts for the polymerization of olefins

A solid catalyst component for the polymerization or copolymerization of olefins comprising:

• titanium, bismuth, magnesium, a halogen, and an electron donor compound which is obtained by a process comprising the following steps:
• (a) dissolving a magnesium halide in a solvent system comprising an electron donor compound and a liquid hydrocarbon at a temperature higher than 40° C., thereby yielding a solution;
• (b) cooling the solution to a temperature below 40° C. and adding a titanium compound in a molar excess with respect to the magnesium halide;
• (c) raising the temperature of the solution to higher than 70° C., thereby obtaining a solid product;
• and
• (d) treating the solid product obtained in step (c) with an excess of titanium halide at a temperature higher than 80° C. for one or more times and recovering the solid particles of catalyst component,
• wherein
• (i) a bidentate electron donor compound is present in step (c), step (d), or both steps (c) and (d) and
• (ii) a Bi compound is present in one or more of the steps (a)-(d).