One of the characteristics of the development of chemical science in the middle of the present century is the vigorous pro­ gress of the "third chemistry," which is often named now the chemistry of heteroorganic compounds. Then in the last decade, among specialists in this field there has been a marked increase in interest in heteroatomic organic derivatives of silicon, i. e. , heteroorganic silicon compounds. However, until recently this new class of chemical substances, which is extremely interesting theoretically and practically, has been without a single specialized monograph which systematizes and generalizes all progress in the heteroorganic chemistry of silicon. The first attempt in this direction was our book "Heteroorganic Compounds of Silicon" [42 (F), 17 (S) *], which appeared at the end of 1966 and was published as an English translation in the USA in 1969. However, as follows from its subtitle "Derivatives of Inorganic Elements," this monograph could not cover the whole broad field of the chemistry of heteroorganic compounds of silicon. The main reason for this was above all the abundance and variety of original investigations of organosilicon derivatives of inorganic elements, which was un­ expected even to the authors themselves. As a result of this the planned length of the book compelled us to omit the sections on organosilicon compounds of phosphorus and sulfur, which had al­ ready been prepared for publication.