A 3D Coordination Network Built from CuII4Cl3(H2O)2 Linear Clusters and Tetrapyridyl Tetrahedral Silane Ligands: Reversible Iodine Uptake and Friedel-Crafts Alkylation Reactions

A novel three-dimensional coordination network 1 in a new 4,5,6-connected topology (4,5,6-T115) built from linear (Cu4Cl3)-Cl-II(H2O)(2) clusters and tetrahedral tetrakis(3-pyridyl)vinylsilane ligands is reported. Utilizing a similar tetrahedral ligand, tetrakis(3-pyridyl)ethylsilane, a different framework 2 having (Cu4Cl3)-Cl-II(H2O)(2) clusters is obtained in tcs topology. The activated sample of 1 shows an excellent and reversible uptake of I-2 in solid as well as in solution phases owing to the presence of uncoordinated chloride ions and electron rich vinylic groups in it. The I-2 uptake studies on the anion-exchanged samples, of bromide, iodide, and nitrate ions, show a progressive decrease in the adsorption capacity with the sample containing uncoordinated Cl- ion showing a maximum uptake of 48.5% and the one with the NO3- ions exhibiting the lowest uptake of 24.0%. These observations suggest that the halide counterions interact better with I-2 in comparison with nitrate ions and the better I2 uptake in the presence of Cl- ions over the other two halides is due to its smaller size that offers a larger surface area for adsorption. Also, both these compounds were shown to be useful catalysts for the solvent-free syntheses of bis(indolyl)methanes via Friedel-Crafts alkylation reaction.