Group 12 elements synthesis

Salts of the [NSO] anion can be used for the synthesis of both transition-metal and main group element thionyl imides by metathetical reactions, e.g., Cp2Ti(NSO)2 and Ph3, .As(NSO)x (x = 1,2), respectively (Section 7.6). 

Reactions of metal halides with polysulfide dianions are useful methods for the synthesis of polysulfido complexes of main group elements and transition metals. In most of these reactions, similarly to other methods, the chain lengths and coordination types of the polysulfide ligands depend on the other ligands coordinated to the metal, on the ratio between the metal and sulfur, on the reaction temperature, and other parameters. 

Two principle strategies have been employed for the synthesis of siloxide-containing molecular precursors. The first involves a silanolysis, or condensation, reaction of the Si - OH groups with a metal amido, alkyl, hahde, or alkoxide complex. The second method involves salt metathesis reactions of an alkali metal siloxide with a metal hahde. Much of our work has been focused on formation of tris(tert-butoxy)siloxide derivatives of the early transition metals and main group elements. The largely imexplored regions of the periodic table include the lanthanides and later transition metals. 

In recent years a large number of hetero- and diheteroalkenes containing heavier main group elements have been obtained by steric protection and/or resonance stabilization of the p(7t)-p(rc)bond. A special challenge was the formation of a P=Si-bond, whose first synthesis was reported by Bickelhaupt etal. in 1984 [1] followed by several others [2-4], but until today no structural information could be obtained. 

Two approaches have been used in the synthesis of these types of compounds. Small boron-phosphorus ring compounds can serve as building blocks, and addition and elimination reactions with other main group elements can then extend the cage structure (see Schemes 23 and 24, Section 12.12.6.4.5). Alternatively, an unsaturated carbenoid fragment can be added to the bicyclic fragment as illustrated in Scheme 31 <1998IC490>. 

There has been great interest in the area of chiral acid catalysts in organic synthesis over the past few decades. This topic has been the subject of several previous reviews. For example, the book Lewis Acids in Organic Synthesis (edited by Hisashi Yamamoto) was published by Wiley-VCH in 2000. In this chapter, successful and significant chiral Brpnsted acid catalysts, chiral Lewis acid catalysts [typical Lewis acidic elements main group elements, B(III) and Al(III), and early transition metal, Ti(IV)], and Lewis acid-assisted chiral Brpnsted acid catalysts developed after 2000 are discussed. Chiral acid/base catalysts wdl be discussed in Chapter 13 by Shibasaki and Kanai. 

The binary representation is applicable to various other oxide materials. However, an important distinction can be made between borates and other main group element oxide systems, such as aluminates and silicates. In the latter systems cations predominantly reside at sites created by the demands of rigid anionic oxide frameworks. Although some degree of structural control may be obtained by varying cations or by use of template synthesis, the oxide frameworks of these systems tend to be relatively inflexible in comparison with... 

In a typical sol-gel synthesis, the metal or the compounds of main group elements undergo hydrolysis and condensation reactions giving gel materials with extended three-dimensional structures. As shown in Equation 5.32 for silicon, addition of an acid or base catalyst to a solution of an alkoxysilane reagent such as tetrame-thoxysilane (TMOS), water and methanol leads to the hydrolysis of the Si-OMe bonds to form Si-OH functional groups. 

TECHNETIUM. [CAS 7440-26-8J. Chemical element symbol Tc, at. no. 43, at. wt. 98.906, penodic table group 7, mp 2l 72 ">C, bp 4877 TT, does not occur in nature. The present location of technetium in die penodic table was vacant for many years, during which time several claims to having found the element were made, but never confirmed. One such claimant termed the element masurium. Technetium has been detected in certain stars and this discovery mnst be resolved with current theories of stellar evolution and element synthesis. 

The methine proton in the keto form and the hydroxyl proton in the enol form of jS-diketones are acidic and their removal generates 1,3-diketonate anions (2), which are the source of an extremely broad class of coordination compounds referred to generically as diketonates or acetylacetonates. The synthesis, structure and properties of these compounds form the focus of this chapter. Di-ketonate anions are powerful chelating species and form complexes with virtually every transition and main group element. The scope of this chemistry is very large and it has been assessed earlier in several excellent reviews.9-14... 

Because of the weakness of the Si-N bond, ring cleavage of cyclosilazanes occurs upon treatment with halides of main group elements. For more than 20 years after the synthesis of the six-membered ring (Me2SiNH)3, only the substitution reaction of the N-bonded hydrogen by one trimethylsilyl group was known.30... 

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