Organosilicon Heteropolymers And Heterocompounds

There are numerous criteria for measuring the growth and development of branches of chemistry. This valuable book illustrates a particular aspect of the growth of organosilicon chemistry. The extent of this field has developed so greatly in recent years that it now is desirable to reclassify parts to bring together hitherto frag mented and relatively disparate sections. This has been accomplished by the presently available large units which have been deSignated as "organosilicon heterocompounds. " Simplified expressions of such classification are structural units of the general type C - Si - heteroelement and heteroelement-C - Si, in which there are attached to the organosilicon moiety elements such as oxygen, nitrogen, metals, etc. This arrangement per mits the correlation of extensive material, which will be invalu able to chemists in many areas, both in and out of organosi- con chemistry. Because of the wealth of information, the authors are currently engaged in the preparation of companion volumes arranged on this general principle. The scope is broad, and includes material which will prove highly interesting and useful to those in academic, industrial, and governmental circles. There is not only a wide coverage of the literature generally, but the listings of patent references and of general reviews and books are among the most complete so far presented.

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 mono graph 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.

Aliphatic Compounds

A very large number of organo derivatives is formed by the Group IV ele ments silicon, germanium, tin, and lead. In comparing the general properties of these elements, Table 1. 1 shows that the first ionization energies decrease (though not in a regular way) with increase in size and atomic number, con sistent with the general increase in metallic character of the elements. Electro negativity values (which have been the subject of considerable controversy) show no clear trend. Although purely inorganic compounds of tin(n) and leaden) are well known, almost all organo Group IV derivatives show an oxidation state of IV. Bonds to carbon become weaker on passing from silicon to lead, as do the element-element bonds themselves. With any particular element M (M = Si, Ge, Sn, or Pb), there is a small decrease in bond energy in the order: M-Ph > M - Me > M - Et. Although accurate data for organo derivatives are lacking, strengths of bonds to other elements probably decrease in the order: M-F> M-O > M-CI > M-H ~ M-N ~ M-S ~ M-Br > M-I, while for a particular element X, the order is: Si-X > Ge-X > Sn-X > Pb-X. It is therefore understandable that reactions leading to Si-F, Si-O, or Si-CI bonds are especially favoured in a thermodynamic sense.