A Family of 1,1,3,3-Tetraalkylguanidine (H-TAG) Solvated Zinc Aryloxide Precatalysts for the Ring-Opening Polymerization of rac-Lactide
✍ Scribed by Julia J. Ng; Christopher B. Durr; Jacob M. Lance; Scott D. Bunge
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 474 KB
- Volume
- 2010
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
Abstract
Reaction of [Zn(μ‐TAG){N(SiMe~3~)~2~}]~2~ {TAG = N=C[N(CH~2~CH~3~)~2~N(CH~3~)~2~] (DEDMG), N=C{[NCH~2~CH~2~CH~2~C^d^H~2~(N–C^d^)]N(CH~2~CH~3~)~2~} (DEPYRG) and N=C{[NCH~2~CH~2~CH~2~CH~2~C^e^H~2~(N–C^e^)]N(CH~2~CH~3~)~2~} (DEPIPG)} with 2 equiv. of ethanol (EtOH) and 2 equiv. of HOAr {OAr = OC~6~H~3~(CMe~3~)‐2‐(CH~3~)‐6 (BMP) or OC~6~H~2~[C(CH~3~)~3~]~2~‐2,6‐(CH~3~)‐4 (4MeDBP)} results in dizinc alkoxides with the general formula [Zn(μ‐OEt)(OAr)(H‐TAG)]~2~ (1–3). Et~2~Zn was additionally treated with 2 equiv. of 1,1,3,3‐tetramethylguanidine (H‐TMG) and H‐BMP or HOC~6~H~3~(C~6~H~5~)~2~‐2,6 to yield [Zn(BMP)~2~(H‐TMG)~2~] (4) and [Zn{OC~6~H~3~(C~6~H~5~)~2~‐2,6}~2~(H‐TMG)~2~] (5). Complexes 1, 2, 4, and 5 were characterized by single‐crystal X‐ray diffraction. Polymerization of rac‐lactide with 1–5 and [Zn(μ‐OMe)(4MeDBP)(H‐TMG)]~2~ (6) were found to generate polylactide (PLA). The bulk powders for all complexes were found to be in agreement with the crystal structures based on elemental analyses, FTIR spectroscopy, and ^1^H and ^13^C NMR spectroscopic studies.