Salen complexes, chiral indium

3 Dinuclear indium complexes bearing chiral salen-type ligands 10.3.1 Chiral indium salen complexes 

As discussed above, A1 catalysts supported by salen ligands are some of the most isoselective catalysts for the polymerization of racemic lactide. However, slow polymerization rates and high water/air sensitivity preclude their use in an industrial setting. We were interested in exploiting chiral indium salen complexes to achieve high activity, selectivity and control over the polymerization process. Although achiral indium salen complexes had been reported previously, prior to our work there was only one example of a chiral indium salen complex, which was not used as a catalyst for polymerization.  

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Complexes ( )- and (R,R)-2 are highly active and controlled for the polymerization of rac-LA yielding a linear relationship between the observed PLA molecular weights and the added monomer, assuming both alkoxides initiate the polymerization, with low molecular weight distributions (Figure 36)." The rate of polymerization with these complexes is first order in lactide concentration with values comparable with the tri-dentate diaminophenolate indium complexes desaibed in Section 2. " -The rates of polymerization are much faster than any of the known chiral aluminum salen systems, which require elevated temperatures and days to reach full conversion." -... 

Figure 34 Synthesis of chiral salen indium complexes with cyclohexyl backbones...

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