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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Nb and Ta benzotriazole or benzoxazole phenoxide complexes as catalysts for the ring-opening polymerization of glycidol to synthesize hyperbranched polyglycerols
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Nb and Ta benzotriazole or benzoxazole phenoxide complexes as catalysts for the ring-opening polymerization of glycidol to synthesize hyperbranched polyglycerols

机译：Nb和Ta苯并三唑或苯并恶唑苯氧化物复合物作为丙啶醇的开环聚合的催化剂合成超支化聚甘油

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摘要

A series of novel mononuclear (1a-7a and 1b-6b) as well as tetranuclear (8a and 9a) niobium (Nb) and tantalum (Ta) complexes of benzotriazole or benzoxazole phenoxide pro-ligands bearing different substituents at the ortho and para positions of the phenol rings were synthesized and characterized. The reaction of NbCl5 or TaCl5 with one equivalent of benzotriazole or benzoxazole phenoxide pro-ligands (L1H-L6H) in dry toluene or chloroform produced the corresponding chloride (1a-6a and 1b-6b) and ethoxy (7a) mononuclear Nb and Ta complexes in high yields. Furthermore, from the mononuclear Nb complexes (1a or 4a), a new structural form of tetrameric niobium complexes (8a and 9a) was synthesized through a controlled hydrolysis reaction. The molecular structures of complexes 1b, 4b, 7a, 8a and 9a were unambiguously confirmed by single crystal X-ray diffraction analyses. Furthermore, all these complexes (1a-9a and 1b-6b) were tested as catalysts for the ring-opening polymerisation (ROP) of glycidol to synthesize hyperbranched polyglycerols (HPG) by using 1,1,1-tris(hydroxymethyl) propane (TMP) as an initiator. The degree of branching (DB) observed was 0.30-0.54, which is an indication of hyperbranched structures. In particular, for the niobium complex with electron-withdrawing substituents on the benzoxazole phenoxide pro-ligand (5a), we achieved superior behavior for the ROP of glycidol in terms of activity, control of molecular weight (M-n) and molecular weight distributions (MWDs) (92% of glycidol to HPG, M-n = 10.52 kg mol(-1), MWDs < 1.33, DB = 0.53 and T-g = -57 degrees C). A highly hydrophilic nature was observed for the synthesized HPG polymer by water contact angle measurement (20 degrees to 35 degrees).
机译：一系列新型单核（1A-7A和1B-6B）以及四核（8A和9A）铌（NB）和钽（TA）复合物的苯并三唑或苯并恶唑苯氧苯基苯萘醌，其在邻位和对位置处造成不同取代基酚环的合成和表征。 NbCl5或TaCl5的与一个当量的苯并三唑或反应苯并恶唑酚亲配体（L1H-L6H）在无水甲苯或氯仿中产生的相应的酰氯（1A-6A和1b-6b）和乙氧基（7A）单核Nb和Ta的复合物高产率。此外，通过单核Nb络合物（1a或4a），通过受控水解反应合成新的四聚铌络合物（8a和9a）的新结构形式。通过单晶X射线衍射分析分析，络合物1b，4b，7a，8a和9a的分子结构明确地证实。此外，所有这些络合物（1A-9A和1b-6b）中进行测试作为催化剂用于缩水甘油的开环聚合（ROP），通过使用1,1,1-三（羟甲基）丙烷合成的超支化聚甘油（HPG）（ TMP）作为发起者。观察到的分支（DB）的程度为0.30-0.54，这是一种超支结构的指示。特别地，对于苯并恶唑苯氧化物Pro-Ligand（5a）上的吸电子取代基的铌络合物，我们在活性，分子量（Mn）和分子量分布的控制方面对缩水甘油的ROP实现了优异的行为（MWDS ）（将甘三种醇的92％至HPG，Mn = 10.52kg mol（-1），MWD <1.33，DB = 0.53和Tg = -57℃）。通过水接触角度测量（20度至35度）对合成的HPG聚合物进行高度亲水性。

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