Inorganic tetravalent chemistry

There are large irregularities in the trends in the stability of Ln and Ln , and hence compounds containing these ions (see Variable Valency, The Divalent State in Solid Rare Earth Metal Halides, and Tetravalent Chemistry Inorganic). 

Lanthanides Coordination Chemistry Organometal-lic Chemistry Fundamental Properties Tetravalent Chemistry Inorganic Variable Valency. 

In order to fully understand the crystal chemistry of the anhydrous LnXs and their solvates ([LnXj(solv) ]), the Ln atomic properties of these species must be considered. The predominant oxidation state for LnX species is the +3 state however, for a number of these cations, tiie +2 (see The Divalent State in Solid Rare Earth Metal Halides) and +4 (see Tetravalent Chemistry Inorganic) states are available. Since the bonding in these compounds is mainly ionic, the cation size and sterics of the binding solvent play a significant role in determining the final crystal structures isolated. The ionic nature of the LnX complexes makes... 

Homogeneous Catalysis Lanthanides Coordination Chemistry Lanthanide Alkoxides Lanthanides Coordination Chemistry Tetravalent Chemistry Inorganic The Electronic Structure of the Lanthanides. 

Lead cations occur in both the divalent (+2) oxidation state, which is the most stable of the group IVB elements, and in the tetravalent (H-4) oxidation state. The divalent oxidation state usually dominates the inorganic chemistry of lead, while the tetravalent state dominates its organic chemistry. The coordination numbers of its divalent compounds range from 2 to 7, while those of its tetrahedral compounds range from 4 to 8. Its stereochemistry is usually octahedral or tetrahedral. 

Another interesting feature of MOFs concerns the number of cations that can participate in the framework. Indeed, compared to inorganic ones [3], which are more based on a few cations (Si and A1 for zeolites, eventually doped with some transition metals, with the exception of titanosilicates [119] Zr, Al, Ga, In phosphates and arsenates, sometimes fuUy substituted by transition metals Ti [72], V [120], Fe [121,122], Co [123,124], Ni [125], Zn [126,127]), MOFs can accept almost all the cations of the classification, at least those which are di-, tri- (including rare earth) or tetravalent. Keeping in mind the tremendous number of species previously isolated in coordination chemistry, this provides a huge number of possibilities for creating new MOFs. 

The inorganic chemistry of lead is dominated by the divalent (2" ) oxidation state rather than the tetravalent (4 ) oxidation state. The divalent state is more dominant in Group IV B elements as the atomic number increases. Dominance of the divalent state occurs because, within Group IV B, there is a decrease in single bond strength with increasing atomic number [13]. 

Tetravalent metal phosphonates (MELS ) are layered compounds that can be considered organic/inorganic polymers. The organic functionality provided by the phosphonate largely determines the surface chemistry of these materials. Choosing phosphonates with an arylsulfonic acid function produces materials that are effective as acid catalysts. This paper describes synthetic procedures used to prepare arylsulfonic acid MELS and methods to increase and stabilize their surface area, porosity, and swelling properties. Acid catalysis by MELS is exemplified by the synthesis of methyl tertiary butyl ether. 

---