Silicon Chemistry I

Contents Low-Valent Silicon H. Biirger, R. Eujen . . . . . . . . . . . . . . . . . . 1 Organometallic Synthesis of Carbosilanes G. Fritz . . . . . . . . . . . . . . . . . . . . . . 43 The Chemistry of Silicon-Transition-MetalCompounds F. H6fler . . . . . . . . . . . . . . . . . . . . . . Author and Subject Index Volumes 26-50 129 Low-Valent Silicon Prof. Dr. Hans BOrger and Dipl. Chem. Reint Eujen Institut f'dr Anorganischc Chemic der Technischen Universit~it, Braunschweig Contents I. II. Introduction . . . . . . . . . . . . . . . . . . 3 Nomenclature . . . . . . . . . . . . . . . . . . 4 Monovalent Silicon 4 . . . . . . . . . . . . . . . . A) General Considerations B) Sill C) Sill ÷ D) Si2 5 . . . . . . . . . . . . . . . . . . . 7 . . . . . . . . . . . . . . . . . . . . 7 . . . . . . . . . . . . . . . 9 F) SiN and HNSi . . . . . . . . . . . . . . . . 10 G) SiO and SiO + . . . . . . . . . . . . . . . . 11 H) SiS, SiSe and SiTe I) SiF L) SiAu . . . . . . . . . . . . . . . 13 . . . . . . . . . . . . . . . . . . . . K) SiCl, SiBr and SiI 14 . . . . . . . . . . . . . . . 16 . . . . . . . . . . . . . . . . . . . Divalent Silicon 17 . . . . . . . . . . . . . . . . . A) General Considerations IV. 4 . . . . . . . . . . . . . . . . . . . . . E) S i - C C o m p o u n d s III. . . . . . . . . . . . . . 17 . . . . . . . . . . . . . 17 B) :Sill 2 . . . . . . . . . . . . . . . . . . . 18 C) :SiF 2 . . . . . . . . . . . . . . . . . . . 20 D) :SiCl2, :SiBr 2 and :SiI2 . . . . . . . . . . . . . 23 E) HSiCI, HSiBr and HSiI . . . . . . . . . . . . . 26 Trivalent Silicon . . . . . . . . . . . . . . . . . . 27 A) General Considerations B) .Sill 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 . . 30 H. Biirger and R. Eujen C) AlkyJsilyl Radicals . . . . . . . . . . . . . . . D) "SiFa ~nd "SiFnH3_ n 30 . . . . . . . . . . . . . . 32 E) "SiCl3 a~d "SiEI,,(CH3)3_,, . . . . . . . . . . . . F) Silyl Anions . . . . . . . . . . . . . . . . . 33 V. Silicides . . . . . . . . . . . . . . . . . . . . 35 VI. References . . . . . . . . . . . . . . . . . . . 36 34 Low-Valent Silicon I. Introduction Except for SIX]- anions and silicides, low-valent silicon compounds exhibiting coordination numbers of 1 to 3 are not stable for long at room temperature. Consequently the structural chemistry of those compounds, which is the subject of this article, has to be based upon investigations at high or low temperature, or upon rapid spectroscopic techniques adapted to the short lifetimes of the species investigated. The reluctance of Si to form compounds analogous to HC-=CH or H2CO is due to its inability to stabilize the coordination numbers 1, 2 or 3 by prrprc bonds, polymeric structures being preferred. On the other hand SiF 2 is thermally more stable than the analogous carbene CF2. The structural and thermodynamic properties of the short-lived silicon compounds are of considerable interest because these species play an important role in reactions at high temperature and in stellar space. The structural prop