C,Y-chelating ligands

The concept of intramolecular coordination by the use of C, Y-chelating ligands of aryl units has been well established. However, the analogous chemistry of its cousin, the three-dimensional carborane, remains relatively unexplored. Recently, o-carborane has attracted much interest due to its ease of preparation and derivati-zation, thermal stability, and steric bulk. The easy preparation of o-carborane can be utilized for preparing useful compounds similar to the C, Y-chelating ligands of... 

II. Divalent Organotin Compounds Containing a C,Y-Chelating Ligand. . 247... 

Fig. 4. Divalent organotin - transition metal compounds containing a C,Y-chelating ligand.

TETRAVALENT ORGANOT1N COMPOUNDS CONTAINING A C,Y-CHELATING LIGAND... 

Depending on the number (one or two) of C,Y-chelating ligands present in diorganotin dihalides, either trigonal bipyramidal or octahedral coordination geometries have been found for the tin center. 

Only a very limited amount of data are available for monoorganotin halides containing a C,Y-chelating ligand. In the solid state, a trigonal bipyramidal coordination geometry for the tin center is preferred. However, in solution when external donor molecules are also present, hexa-coordinate species may be formed. 

Triorganotin Halides Containing Other C, Y-Chelating Ligands... 

Only a few examples of monoorganotin trihalides in which a C,Y-chelating ligand is present are known. Because of their importance as precursors for PVC stabilizers, some structural investigations on ester—tin trihalides have been carried out. 

It has been shown that C,Y-chelating ligands can stabilize divalent or-ganotin compounds to such an extent that these compounds can be isolated as well-defined monomeric species. It is very likely that as result of intramolecular coordination, the tin atom is shielded in such a way that polymerization is prevented. Application of bis-orthochelating aryldi-amine ligands allowed the synthesis of stable mixed diaryltin(II) compounds. 

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