The present disclosure relates to a catalyst component for the polymerization of olefins comprising Mg. Ti and an electron donor such as mercaptoester derivatives of the general formula (I). in which Z is selected from C, Si, O, N, S or P, with the proviso that the atoms O, S, P and N are not directly linked to either the carboxylic group or the sulfur atom of formula (I), the R2 groups, equal to or different from each other, are selected from hydrogen or a C1-C20 hydrocarbon radicals, optionally containing a heteroatom selected from halogen, P, S, N, O and Si, which can be fused together to form one or more cycles, m is a number satisfying the valences of Z and n is an integer ranging from 1 to 10, X is O or S, Y is —OR3, —NR4R5) or R6 groups in which R1 and R3 are selected from C1-C15 hydrocarbon groups, optionally containing a heteroatom selected from halogen, P, S, N, O, and Si, R4-R5 groups, independently, are hydrogen or R1 groups, and R6 groups have the same composition as R1 groups.