(1) a compound obtained by treating an oxide of an element of Groups II-IV in the Periodic Table with a compound represented by the general formula R1 m Si(OR2)n X4-m-n wherein R1 and R2 are each a hydrocarbon radical having 1 to 24 carbon atoms, a hydrocarbon radical containing oxygen, sulfur or nitrogen, or hydrogen, X is a halogen atom, m is 0???m<4 and n is 0???n???4, provided 0???m+n???4,