TMPZnN(SiMe₃)₂, [TMPZn(μ-OⁱPr)]₂ and TMPZn[OCMe₂C(O)OEt]. Their role in the ring-opening of rac-lactide and ε-caprolactone where TMP = 1,5,9-trimesityldipyrromethene

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• 作者：Vagulejan Balasanthiran^a ; Malcolm H. Chisholm^a ; ^{Chisholm@chemistry.ohio-state.edu" class="auth_mail" title="E-mail the corresponding author} ; Kittisak Choojun^b ; Christopher B. Durr^a ; Pasco M. Wambua^a
• 关键词：Polylactic acid ; Polycaprolactone ; Ring-opening polymerization
• 刊名：Journal of Organometallic Chemistry
• 出版年：2016
• 出版时间：15 June 2016
• 年：2016
• 卷：812
• 期：Complete
• 页码：56-65
• 全文大小：2207 K

文摘

From the reaction between Zn[N(SiMe₃)₂]₂ and TMP-H (1 equiv.) in toluene at room temperature TMPZn[N(SiMe₃)₂] was prepared and subsequently reacted with PrⁱOH (1 equiv.) and HOCMe₂C(O)OEt (1 equiv.) to give [TMPZn(μ-OPrⁱ)]₂ and TMPZn[OCMe₂C(O)OEt], respectively. The three compounds were each crystallized and characterized by single crystal X-ray diffraction. The compound TMPZn[N(SiMe₃)₂] was a three coordinated N₃Zn compound with an anagostic N(SiMe₃)₂ ligand where one SiMe₃ was annexed to the Zn²⁺ ion. The compound [TMPZn(μ-OPrⁱ)]₂ has a molecular C₂ axis and is dimeric in toluene-d₈ solution having a N₂ZnO₂ core for each Zn²⁺ ion. In TMPZn[OCMe₂C(O)OEt] compound the Zn₂ + ion is four-coordinated. This too is present in solution (IR) and also present in toluene-d₈ and THF where there is evidence of fluxionality with T_c ∼15 °C and −85 °C, respectively. The compound [TMPZn(μ-OPrⁱ)]₂ polymerizes both ε-caprolactone (ε-CL) and rac-lactide (rac-LA) to give polycaprolactone (PCL) and polylactic acid (PLA), respectively. The rate of the reactions are ε-CL > LA and are influenced by the nature of solvent, THF > CD₂Cl₂/CH₂Cl₂. The nature of PLA derived from rac-LA is heterotactic: P_r = 0.96 in THF and P_r = 0.75 in CD₂Cl₂/CH₂Cl₂. In the copolymerization of rac-LA: ε-CL by both [TMPZn(μ-OPrⁱ)]₂ and TMPZn[OCMe₂C(O)OEt] only PLA is produced, PCL is not formed.