Subject silicon compounds

Hypervalent silicon compounds have generated much interest in recent years. This is evident from the numerous papers published every year on this topic, and from the extensive reviews which have appeared in recent years1-7. In this review we have attempted to cover only the most recent (five year) literature. Only for subjects for which we felt that the new work would not be fully appreciated without the previous reports did we include earlier citations, or for those subjects which in our judgment, were not sufficiently covered in earlier reviews. 

This chapter will summarize the recent advances in hydrosilylation and related reactions catalyzed by transition metal complexes since this subject was reviewed in The Chemistry of Organic Silicon Compounds in 1989 that covered the advances till the end of 19863. 

Leather can also be waterproofed. Treated with silicone compounds, leather is very resistant to water and is not subject to rot, mildew, etc. Waterproof leather is used to manufacture waterproof shoes, clothes, sports goods. 

Compounds containing silicon bonded to only one other atom are unstable and are usually only generated and observed as reactive intermediates of short half-life. Silicon compounds subjected to flash photolysis or electrical discharges in the gas phase produce short-lived species SiX (X = H, F, Cl, Br, I, C, Si, etc.), the band structure of which have been studied in detail. The structures, electronic configurations, and so on of Six (X = H, F, Cl, Br, I, N, O, etc.) have also been the subject of MNDO (modified neglect of diatomic overlap) and other calculations. ... 

Silicon only has one naturally occurring isotope ( Si) with a nonzero nuclear spin and Si NMR spectroscopy has become one of the most widely used techniques for the identification of silicon compounds. Unfortunately, the natural abundance of Si is only 4.7%, which combined with its long spin-lattice relaxation times, means that relatively long acquisition times may be needed to obtain high quality spectra. Si NMR spectroscopy has been the subject of a number of reviews and tables of chemical shift data and coupling constants are available. " ... 

Comparative studies with a series of twelve C/Si pairs of the meprobamate/sila-meprobamate type (68a/68b) also revealed, with only a few exceptions, great similarities in the biological properties of the respective C/Si analogues138 (for structurally related silicon compounds see also Reference 142). The C/Si pairs were tested for their acute toxicity, and for sublethal activity the rotating rod test and the extension of hexobarbital sleeping time were used (mice, intraperitoneal administration). In addition, the metabolism of sila-meprobamate (68b) and some of its derivatives was studied139 (for this subject see Section IV). 

The chemistry of organic silicon compounds is one of the fastest growing fields in organic chemistry. In this subject, theory often precedes and sometimes even directs experimental work and this is reflected in a comprehensive and detailed theoretical chapter. Several exciting new developments of organosilicon chemistry of the last decade have been reviewed, such as multiple bonds to silicon. 

The hydrolysis of (EtO)4Si (and the subsequent polycondensation of Si-OH containing molecules) has been the subject of considerable investigation because of its importance in the fabrication of glasses and colloidal silica via the sol-gel process see Sol-Gel Synthesis of Solids). Hydrolysis of the Si-0 bond in alkoxysilanes is also very widely used to attach silicon compounds to surfaces and in coupling reactions. The fundamental reaction types involved in the formation of polymeric silica materials (via, for example, cyclic oligomers similar to those shown in Figures 4 and 5) from monomeric (RO)4Si compounds are shown in Scheme 43. 

The first example of the hydrosilylation, that is, the reaction occurring between trichlorosilane and 1-octene in the presence of acetyl peroxide, was reported in 1947 by L. H. Sommer (1), but the discovery in 1957 of hexachloro-platinic acid as a very efficient catalyst by J. L. Speier (2) from Dow Coming became a strategic point for wide and common application of the reaction as one of the most fundamental and elegant methods explored over the next 50 years for laboratory and industrial synthesis of organosilicon and other related silicon compounds, which can also be directly subjected to organic synthesis. 

Among multiple-bond-containing silicon compounds, neutral HNSi holds a special place. The [H,N,Si] potential energy surface and several possible N- and Si-substituted isomers have formed the subject of several experimentaP " and theoretical investigations . In a recent experimental and theoretical study, the ionic as well as the neutral [H,N,Si] surfaces were explored . Ionization of a mixture of iodosilane and NH3 gives rise to [H,N,Si]+ cations, which according to CA experiments exist in an N-protonated (65) rather than the isomeric Si-protonated form (66). 

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