PURPOSE: To provide the subject new compound useful as an electron donating compound in producing α-olefin polymers in the magnesium chloride-carrying type Ziegler-Natta catalytic system.

CONSTITUTION: The objective compound, 2-trimethoxysilyladamanthane of the formula, which can be obtained, for example, by reaction of tetrachlorosilane with a 2-adamanthyl Grignard reagent (e.g. a 2-adamanthyl magnesium halide) and removing the magnesium salt formed through filtration followed by distilling the solvent off the filtrate and then reaction of the filtrate with methanol in the presence of a dehydrohalogenating agent pref. at 60-80°C for 2-6hr.