Carbon compounds and complexes

V.7 Group 14 compounds and complexes V.7.1 Carbon compounds and complexes V.7.1.1 Nickel carbonates... 

XLl Carbon compounds and complexes XI.1.1 Solid thorium carbides... 

A few carbon compounds are considered to be inorganic. These include carbon dioxide, CO2, and and carbon compounds containing complex negative ions (for example, CO32-, HCO3-, and 0CN-). 

Tetrahedral Four-Coordinate T-4 In contrast to the chemistry of carbon compounds, and some main group compounds such as the structure shown in Figure 5.4, Werner-type T-4 coordination complexes are too labile to isolate in solution as individual enantiomers. The presence of chiral ligands can influence the racemic (diastereomeric) equilibrium and make the preparation and isolation of... 

The Cambridge Structural Database contains X-ray crystallographic data for aU reported compounds and complexes of cobalt that contain carbon (see X-ray Crystallography). The November 2002 version of this database lists 10403 structures containing cobalt, with the earhest, the Co(n) complex of the phthalocyaninate dianion, dating back to 1936. The Inorganic Crystal Stmcture Database contains stmctural data for cobalt compounds... 

All of the members of the final review team contributed, if not text, then comments to all of the chapters of the book. Their primary responsibilities for the different sections/chapters were divided as follows. Paul Brown prepared the introduction, and the sections on elemental zirconium, the zirconyl ion, the gaseous zirconium oxides, zirconium hydride, the halogen compounds and complexes, the chalcogen compounds and complexes, the Group 15 compounds and complexes, zirconium carbides and silicates. He was assisted by Christian Ekberg in the interpretation of aqueous zirconium complexes in these sections. Some initial work was done by Ken Jackson on the zirconium sulphate, nitrate and phosphate compounds and complexes. Bernd Grambow was responsible for the drafting of the sections on zirconium hydrolysis, the ion and the section on crystalline and amorphous zirconium oxides. Enzo Curti drafted the section on the zirconium carbonates. 

The result is that the first element of the main groups (lithium, beryllium as well as boron, carbon, nitrogen, oxygen, and fluorine described in Chapter 12) are different from the rest of their group members. Usually, the first element is much smaller than the rest of the elements in that group, and it tends to form covalent compounds and complexes. This tendency is called Fajans rule after Kazimierz Fajans, a physical chemist who in 1923 postulated it. 

Humic substances, which are biopolymers widely and abundantly present in natural waters and soils, also have a high complexing ability with various heavy metal ions. These compounds are formed by the random condensation of breakdown products of terrestrial and aquatic plants and extracellular metabolites of phytoplankton. Concentrations of metals in marine and fresh waters are often higher than predicted from the solubility products of corresponding hydroxide and carbonate compounds. The complexation of metal ions with dissolved humic substances is responsible for the apparent supersaturation of metals in natural waters [9-21], Water-soluble humic substances are usually divided into two fractions, humic acid (HA) and Mvic acid (FA). HA is defined in operational terms as the fraction of humic substance soluble in alkaline solutions and insoluble in acidic solutions, while FA is the fraction soluble in both alkaline and acidic solutions. A general method for the fractionation of humic substances is illustrated in Fig. 1. HA is easily obtained as a precipitate in acidic solution (pH < 1.5). Although HA appears to be an attractive adsorbent for the recovery of heavy metal ions, there is little information on its practical application as adsorbent. It is difficult to use humic acid as the adsorbent because of its high solubility in water. 

Cycloheptatrienyl and cyclotatetraene complexes, like other sandwich compounds, and complexes [M(C H )L ] containing polyelectron ligands are thermally stable. Often, these compounds melt at higher temperatures without decomposition. Complexes with ligands which do not contain bulky substituents connected to the ring carbon atoms are usually very sensitive to oxidation and hydrolysis. The compounds of the type M(C0T)2 (M = U, Pa, Ce, etc.) are easily oxidized but are more resistant to water. Table 8.1 gives properties of some cycloheptatrienyl and cyclooctatetraene metal compounds. 

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