Homoleptic complexes solution properties

The simple homoleptic complex Sn(Oct)2 catalyzes lactide polymerization both in solution and in the melt at temperatures >130°C and is the most widely used catalyst for lactide polymerization industrially. As previously mentioned, commercially available lactide with >90% L-LA polymerized with Sn(Oct)2 will generate -90% isotactic PLA. While this material has commercial applications, its thermal and mechanical properties are not suitable for many applications where polyolefins are typically used. One way to improve the polymer properties is by increasing the isotacticity or forming isotactic stereoblock PLA through stereoselective polymerization of L- and D-LA mixtures. However, this cannot be achieved with Sn(Oct)2 and other simple initiators. ... 

These elements form homoleptic allyl complexes as well as alkenyl compounds with mixed coordination spheres. These compounds are also sensitive to air and proton containing solvents (Table 7.8). They decompose at low temperatures, for example, the compound [Ta(C3115)4] is stable only in saturated hydrocarbon solutions below 273 K. The complexes [Nb(allyl)4] and [Ta(allyl)4] are paramagnetic. The complex [V(C3H5)3] has pyrophoric properties. Halogen and cyclopentadienyl allyl complexes are more stable. In the compound [V(C3H5)cp2] the allyl forms a a bond to the central atom thus, it acts as an ligand. 

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