Ziegler natta catalyst components for the polymerization of olefins

catalyst components for olefin polymerization comprising groups of Mg, Ti, Cl, OR where R is a C1-C10 optionally containing heteroatoms, and an ether having two or more ether groups, wherein the weight ratio Mg / Ti is less than 3, the weight ratio Cl / Ti is between 1, 5 and 6, the weight ratio OR / Ti is between 0, 5 and 3, 5 and at least 50% of the atoms titanium is in a state of less than 4 valence.