Organometallic compounds chelation

Diastereoselective addition of a wide range of Grignard reagents to C -alkyl and C-aryl-A-[a.-phenyl- or u-methyl-j3-(benzyloxy)ethyl nitrones is determined by the presence of a stereogenic A -substituent (136, 137). High diastereoselectiv-ity in the addition of organometalic compounds to A-(( i-methoxyalkyl) nitrones can be explained by a simple chelation model (Scheme 2.132) (136). 

Nowadays we look with other eyes at organometallic compounds the family of which has expanded enormously. Some members of this family are soluble in water due to their ionic nature the legions of anionic carbonylmetallates (e.g. [Ni(CN)(CO)3] ) and cationic bisphosphine Rh-chelate complexes (e.g. [Rh(BDPP)(COD)] ) just come to mind. Others obtain their solubility in water from the well soluble ligands they contain these can be ionic (sulfonate, carboxylate, phosphonate, ammonium, phosphonium etc. derivatives) or neutral, such as the ligands with polyoxyethylene chains or with a modified urotropin structure. 

During the 25-year history of atomic layer deposition several volatile compounds of different chemical nature have been studied for deposition processes. Typically these volatile compounds have been either metals, halides, nitrates or inorganic chelates and, more recently and still relatively rarely, true organometallic compounds. Systematic studies have typically been carried out using metal alkyls and cyclopentadienyl-type compounds. 

Solid or liquid organometallic compounds such as ferrocene and its various derivatives, iron (III) acetyl acetonate, metal chelates etc. 

The exploitation of atomic-absorption spectrophotometry for monitoring HPLC column effluents has been recently examined by Funasaka et al. [46]. An eluent-vaporizing system was designed which introduced the effluent into the atomic-absorption unit. The limit of detection of compounds such as ethylmercury chloride was ca. 10 ng compared to 30 jug for a UV detector at 210 nm. The extreme selectivity of atomic absorption could make this technique of great value for the analysis of trace amounts of organometallic compounds and metal chelates. 

Lin, Y. Smart, N.G. Wai, C.M. Supercritical fluid extraction and chromatography of metal chelates and organometallic compounds, Trends Anal. Chem. 14 (1995) 123-133. 

All the standard texts listed in Section A.3 of the Appendix have lengthy sections on coordination and organometallic compounds of the transition elements. See also the books listed in Sections A.10 and A.ll. Bell (1977) gives the fullest account of the chelate effect. Cotton and Wilkinson (1988) (Section A.3) is best for the catalytic applications of complexes. Jolly (1984) (Section A.3) discusses electron-counting in polynuclear carbonyls in some depth. 

Thus, use of ultrasound is very common in chemical processes, first of all in the optimization of syntheses of organic compounds, which are out of the area of the present book. Classic coordination compounds, such as, for example, metal chelates, synthesized by this technique, are not sufficiently represented in the available literature. More attention is paid to US preparation of a- and Ji-organometallic compounds, mainly s- and p-metals (Li, Mg, Al), which frequently serve as precursors for organic synthesis reactions. 

In addition to metal complexes and chelates, another major type of environmentally important metal species consists of organometallic compounds. These differ from complexes and chelates in that the organic portion is bonded to the metal by a carbon-metal bond and the organic ligand is frequently not capable of existing as a stable separate species. 

What distinguishes organometallic compounds from metal chelates ... 

In 7 two chelating benzamidinate anions are centered around a nearly linear O-Na-Na-O unit (Fig. 2) [34], With 2.741(4) A the Na(l)-Na(2) distance is the shortest Na --Na contact found in any organometallic compound containing sodium. 

---