Tetravalent chemistry inorganic compounds

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). 

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... 

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. 

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. 

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