Silicon Germanium, Tin, and Lead

Silicon, Germanium, Tin, and Lead.—Ihe mass spectra of the tetrakis(penta-fluorophenyl) derivatives (CgFs)4M (M = Si, Ge, Sn, or Pb) have been studied. Rearrangements involving transfer of fluorine to metal, with or without charge, are prevalent. The heavier metal species give simpler spectra, and the bulk of the ion current is carried by fluorocarbon ions for the silicon compound and by metal-containing ions, particularly MF, for the other compounds.  

Sulphur.—Pentafluorobenzenesulphenyl chloride, prepared by chlorination of CsFs SH or of Its lead(ii) salt, gives the pseudohalides C3F3-SX (X = CN, NCO, or SeCN) upon treatment with the corresponding silver salts. Pentafluorobromoboizraie and pentafluorobenzenethiol react with two equivalents of butyl-lithhim to give perfluoro-dibenzothiophen, possibly via 

Spinney, Inerg. Nuclear Chem. Letters, 1970,6,509. 

The crystal structures of the palladium (84) and platinum (85) penta-fiuorobenzenethiolato-complexes have been described. 

Following its painstaking investigation of the benzene-cobalt trifluoride reaction, which played such an important part in the development of aromatic fluorocarbon chemistry, the Birmingham group has studied in some detail the fluorination of tetrahydrofuran with cobalt trifluoride and with potassium tetrafluorocobaltate(in) as a prelude to an investigation of poly- 

This chapter is devoted to the chemistry of two of the oldest known elements, tin and lead, and two that are of much more recent discovery, silicon (1824) and germanium (1886). The elements in Group IVA show the trend toward more metallic character in progressing down in the group. Silicon is a nonmetal, tin and lead are metals, and germanium has some of the characteristics of both metals and nonmetals. These elements are all of considerable economic importance, but in vastly different ways. 

Tin and lead have been known since ancient times. Cassiterite, Sn02, was mined in Britain and transported by sea to the Mediterranean area where copper was available. After reducing the Sn02 with charcoal to produce tin, the tin was alloyed with copper to make bronze as early as about 2500 BC. Consequently, tools and weapons made of bronze figured prominently in the period known as the Bronze Age (about 2500 to 1500 BC). At an early time, lead was found as native lead or as galena, PbS, that could be converted to the oxide by roasting the sulfide in air followed by reduction with carbon. As a result, tin and lead are among the elements known for many centuries. Of course, the reason that the metals Sn, Cu, Au, 

and Pb were available to the ancients is that either they were found uncombined (native) or they were easily reduced with charcoal (carbon). Today, the major sources of tin are Britain, Malaysia, Indonesia, and China. 

Silicon was discovered by Berzelius in 1824. Although knowledge of the element itself is fairly recent, compounds of silicon have been known for thousands of years. For example, pottery, brick, ceramics, and glass are made of silicates that are naturally occurring materials. In addition to these uses of silicates, highly purified elemental silicon is used in the manufacture of integrated circuits or chips that are used in the electronics industry. It is also alloyed with iron to make Duriron (Fe, 84.3% Si, 14.5% Mn, 0.35% and C, 0.85%), an alloy that resists attack by acids. This alloy is used in the manufacture of drainpipes and the cores of electric motors. 

Silicon is an abundant element that makes up 23% of the earth s crust, primarily in the form of silicate minerals and Si02 (sand, quartz, etc.). The name silicon is derived from the Latin names si lex and silicus, which refer to flint. The element is a brittle solid that has the diamond 

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Silicon, germanium, tin and lead can make use of unfilled d orbitals to expand their covalency beyond four and each of these elements is able (but only with a few ligands) to increase its covalency to six. Hence silicon in oxidation state -f-4 forms the octahedral hexafluorosilicate complex ion [SiFg] (but not [SiCl] ). Tin and lead in oxidation state -1-4 form the hexahydroxo complex ions, hexahydroxostannate(IV). [Sn(OH) ] and hexahydroxoplum-bate(IV) respectively when excess alkali is added to an aqueous solution containing hydrated tin(IV) and lead(IV) ions. 

Lead has only one form, a cubic metallic lattice. Thus we can see the change from non-metal to metal in the physical structure of these elements, occurring with increasing atomic weight of the elements carbon, silicon, germanium, tin and lead. 

Compare and contrast the chemistry of silicon, germanium, tin and lead by referring to the properties and bond types of their oxides and chlorides. 

Not applicable to silicon, germanium, tin, and lead perhydro- is prefixed to the name of the corresponding unsaturated compound. 

It has become common to classify all molecular compounds, which fulfill the above characteristics, as carbene analogs 9,13>. As a consequence, compounds of divalent silicon, germanium, tin, and lead may be regarded as carbene-like and are therefore called silylenes, germylenes, stannylenes, and plumbylenes. In contrast to carbenes they have one property in common the energetically most favorable electronic state is the singlet 1a2 found by experiments and calculations 9). 

X-ray Crystal Structure and GED Data of the Decamethylmetallocenes of Silicon, Germanium, Tin, and Lead... 

Arkles BA (1995) Silicon, germanium, tin and lead compounds metal alkoxides, diketo-nates and carboxylates a survey of properties and chemistry. Gelest, Tullytown PA... 

M. Weidenbmch, Some Silicon, Germanium, Tin and Lead Analogues of Carbenes, Alkenes, and Dienes, Eur. J. Inorg. Chem. 1999, 373. 

HP Calhoun, CR Masson. In M Gielen, ed. Reviews on Silicon, Germanium, Tin and Lead Compounds. Tel-Aviv Freund, 1981, p 153. 

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