To obtain a new compound useful as an electron donor in an olefin polymer catalyst system.

This new compound is represented by the formula [R1 is a 1-22C alkyl, a 3-22C cycloalkyl, etc.; R2 is a bis (1-22C alkyl or 3-22C cycloalkyl) amino, clecahydroqunolynyl, etc.; R3 is a 1-8C alkyl or a 3-8C cycloalkyl], e.g. 3,3,3-trifluoropropyl(2-trimethylsilylpiperidinyl)dimethoxysilane. The compound is obtained by reacting, e.g. an anion derived from an 11-22C alkane or a halide- substituted alkane with a silane (e.g. tetrachlorosilane) and treating the reaction product with an alkoxide (e.g. methoxide) and subjecting the resultant compound to substitution reaction with a substituted secondary amine or a cyclic amine.