Zinc-BDI complex

Coates eta/, have developed a series of single-site zinc-BDI complexes 20 and 21 for the co-polymerization of epoxide with Design concept of the zinc complexes is a combination of (i) monoanionic chelating BDI ligand, which... 

Table 5 Alternating co-polymerization of CHO with CO2 catalyzed by zinc-BDI complexes...

Following the detailed mechanistic study using BDI zinc complexes, Coates subsequently reported a dinucleating BDI ligand the p-oxo-5-diimine (BODDI) ligands (Fig. 20) [149]. The reaction of the corresponding dinuclear zinc ethyl complexes with acetic acid afforded zinc acetate systems (with a Zn-Zn distance of 3 A), but no catalytic activity was reported. 

It has been found that magnesium complexes supported with bidentate p-diketiminate are more active in the ROP of l- and rac-lactide than their structurally analogous zinc complexes. Faster rate of polymerization of magnesium complexes were such that an almost complete conversion (97%) occurred in 1 min at 20 °C for a p-diketiminate magnesium complex [(BDI-l)Mg(0 Pr)]2 31 (O Pr = isopropoxide) whereas the zinc analog needed 33 min for a similar conversion at the same temperature [64] (Table 3, entry 1). Similarly a higher... 

In 1999, Nozaki and co-workers were the first to report an asymmetric copolymerization, catalysed by a chiral amino-alkoxide zinc complex 15 (Table 6) and producing optically active PCHC with 70% ee (measured by hydrolysing the copolymer and analysing the resulting diol using chiral GC) [138,148], The crystal structure of the catalyst, reported subsequently, showed a dimeric structure it was unclear whether the dimer was maintained during the copolymerization [148], In the solid state, the zinc-zinc distance in the catalyst was determined to be 3.00 A (vs. ca. 4 A, for the loosely bound BDI zinc dimers). 

We previously showed that well-defined, structurally characterized P-diiminate (BDI) zinc complexes (Figure 1) catalyze the ring-opening polymerization of cyclic esters (22,23) and the alternating copolymerization of... 

---