Inorganic and Materials Synthesis

In the area of renewable materials, bulk oxypropylation of chitin and chitosan has been performed. Chitin and chitosan are abundant natural polymers obtained from shellfish, such as crab shell or shrimp shell. This solvent free reaction yields viscous polyols. Unfortunately, propylene oxide homopolymer is formed as a by-product but is easily separated. It should be noted that care was taken to minimize the risk involved in the use of toxic, flammable propylene oxide (the reagent in this process). 

Solvent free methods have been used extensively in supramolecular chemistry, coordination chemistry and the formation of transition metal clusters and polymers. Reactions range from very simple ligand substitution reactions for salts of labile metal ions to more complex procedures, some of which are outlined below. 

Calix[4]resorcinarenes, which can be used as supramolecular building blocks, have been prepared in high yields and purity using a solvent free approach. Equimolar quantities of the benzaldehyde and resorcinol, in the presence of /7-toluenesulfonic acid, were ground together using a mortar and pestle 

A reversible solid-state HCl elimination reaction from a Cu(ii) pyridinium coordination complex has been reported. The reaction proceeds with a colour change from yellow (pyridinium complex) to blue (pyridine complex). This reaction suggests that other protic ligands may successfully be coordinated to metals using a solvent free approach in the future. 

In an interesting twist on the solvent free reaction, Petrukhina and coworkers co-sublimed a volatile metal complex, [Rh2(CF3C02)4], and arene molecules including paracyclophanes to yield organometallic coordination polymers. Moderate yields of crystalline products were obtained (35-70%), 

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