To obtain a new compound having a tertiary or secondary hydrocarbon group at the α-position with respect to the silicon atom and useful in the medicinal synthesis or agrochemical field.

This compound is a compound of the formula, RuR1ySi(A)a (A is of formula I or II; R is H or a 1-20C monovalent hydrocarbon substitutable with halogen(s) or the like; R1 is branched at the α-position with respect to the silicon atom and a 3-30C monovalent hydrocarbon substitutable with O or the like; E is e.g. N substituted with a 1-20C monovalent hydrocarbon substitutable with N or the like; (u) is 0-3; and (a) and (y) are each 1-3), for instance, 2-(t-butyldimethylsilyl)-1-methylimidazole. The compound is obtained by reacting a compound of formula III or IV (M is a group or subgroup 1 to 3 metal) (e.g. 2-lithio-1-methylimidazole) with a compound of the formula, RuR1ySi(X)a (X is a halogen) (e.g. t-buthyldimethylchlorosilane).