Zinc, organo- compounds preparation

The zinc alkyls, of which this is an example, are vile-smelling inflammable liquids. They were the first organo-metallic compounds prepared by Frankland in 1849. With water, they decompose giving an alkane ... 

Chromium (III) chloride forms adducts with a variety of donor ligands. The tetrahydrofuran complex CrCl3-3THF, which is obtained as violet crystals by action of a little zinc on CrCl3 in THF, is a particularly useful material for the preparation of other chromium compounds such as carbonyls or organo compounds, as it is soluble in organic solvents. 

Support-bound transition metal complexes have mainly been prepared as insoluble catalysts. Table 4.1 lists representative examples of such polymer-bound complexes. Polystyrene-bound molybdenum carbonyl complexes have been prepared for the study of ligand substitution reactions and oxidative eliminations [51], Moreover, well-defined molybdenum, rhodium, and iridium phosphine complexes have been prepared on copolymers of PEG and silica [52]. Several reviews have covered the preparation and application of support-bound reagents, including transition metal complexes [53-59]. Examples of the preparation and uses of organomercury and organo-zinc compounds are discussed in Section 4.1. 

After the investigation of Frankland and Kolbe mentioned above, Frankland in the following year heated metallic zinc with alkyl iodides, and besides preparing paraffin hydrocarbons in this way, he also discovered the zinc alkyls, the first of the organo-metallic compounds,1... 

He will notice the use of aluminium chloride in the preparation of various aromatic compounds, will hear the story of the discovery of the zinc alkyls, and will possibly be attracted by those interesting bodies, the organo-metals. 

There are many examples of asymmetric addition of organo-metallic reagents to aldehydes (chapter 27) and the one that works here uses Seebach s TADDOL 51 as a ligand for zinc.8 The TAD-DOL 51 is prepared from tartaric acid and used as its titanium (IV) complex to catalyse the addition of the organozinc compound to acrolein. After photochemical cyclisation in the presence of Cu(I), the bicyclic alcohol 53 was isolated in good yield and >98% ee. 

Organosilicon compounds were prepared by the metathesis reaction of organo-zinc compounds with silicon tetrachoride as shown in eq. (2.11) in 1861. However, in 1941, Rochow [32—34] developed a direct reaction method with a copper catalyst, and a great amount of organosilicon compounds were easily prepared by this reaction method. Organosilicon compounds have become rapidly more numerous and 600 00 tons or more were produced in 1994. Thus they became the organometallic compound produced in the largest amount [34a,34b]. 

Formation of Zincate Complexes. Zincate compounds such as K(ZnCH2SiMe3)3 are formed in a transmetalation reaction of bis[(trimethylsilyl)methyl]zinc with elemental potassium, or by reaction with potassium salts. Lithium zincates such as Li[Zn(CH2SiMe3)2R] [R = Me, Ph, N(SiMe3)2] can be prepared by reacting the title compound with the corresponding organo-lithium compounds.Transmetalation with alkaline earth metals such as strontium, barium, and calcium affords zincates of the type illustrated in eq... 

It is expected that endothermic or weakly exothermic organometallic compounds will be the most versatile reagents RM in such reactions. Such compounds are found among the heavy B elements (Hg, Tl, Pb and Bi). Of these the air-stable and readily prepared (though toxic) organo-mercury compounds are the most widely used. Let us consider the heats of reaction between dimethyl mercury and zinc and cadmium ... 

A seledive cross-coupling readion of (Z)-2,3-dibromopropenoate 457 with organo-zinc compounds allows the preparation of highly fundionalized enoates such as 458 (Scheme 7.113). 

---