Heteroatom-substituted crystal structure

Crystal structures of ortho-substituted phenyl tellurium halides and of J-phenyl-3-(4 -methoxyphenyl)-l-propen-l-yl tellurium chloride6clearly show that tellurium interacts with the heteroatom, thus stabilizing the compounds. In the absence of a stabilizing group in the ortho-position, aryl tellurium halides are probably polymeric as solids and in solution with... 

In the attempt to synthesize molecular sieves with isomorphous substitutions of A1 and/or Si by the divalent calcium element in the tetrahedral positions, we obtained a new calcium silicate phase by inclusion of heteroatom calcium into silicate sols. The characterization results showed that as-synthesized calcium silicate, named CAS-1 (Calcium silicate No. 1), was a novel zeolite-like crystal material with the cation reversibly exchangeable and selectively adsorptive properties. In this paper, the effects of composition of raw materials, reaction temperature and the different alkali ion on the hydrothermal synthesis of calcosilicate crystal material CAS-1 were investigated and the uptake of different cation on the thermal stability of CAS-1 structure was also examined. The sample was characterized by XRD, TEM, SEM, DT-TGA, BET, AAS and chemical analysis. 

When a methylene group spacer is inserted between the ortho heteroatom and the carbanionic center, the coordination geometry of the anionic center is no longer restricted to be planar for intramolecular chelation to occur. Hence, o-(dimethylaminomethyl)phenyllithium (126) crystallizes from an ether/hex-ane solution as the internal-chelated tetramer (127). This structure is analogous to tetrameric phenylli-thium (119). When an additional dimethylaminomethyl group is substituted at the ortho position as in 2,3,5,6-tetrakis(dimethylaminomethyl)phenyllithium, the aggregate crystallizes as the dimer (128). Hie lithium atoms in both (127) and (128) are coordinated to four other nonlithium atoms this coordination can only be achieved by dimerization and tetramerization respectively. 

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