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首页> 外文期刊>Chemistry: A European journal >Bis(phosphinimino)methanide borohydride complexes of the rare-earth elements as initiators for the ring-opening polymerization of ε-caprolactone: combined experimental and computational investigations
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Bis(phosphinimino)methanide borohydride complexes of the rare-earth elements as initiators for the ring-opening polymerization of ε-caprolactone: combined experimental and computational investigations

机译：作为ε-己内酯开环聚合反应引发剂的稀土元素双（膦亚氨基）甲烷甲烷硼氢化物配合物：结合实验和计算研究

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Rare-earth-metal borohydrides are known to be efficient catalysts for the polymerization of apolar and polar monomers. The bis-borohydrides [{CH(PPh _2NSiMe_3)_2}La(BH_4)_2(THF)] and [(CH(PPh2N?iMe.,)2}Ln(BH_4)_2] (Ln = Y, Lu) have been synthesized by two different synthetic routes. The lanthanum and the lutetium complexes were prepared from [Ln(BH_4)_3(THF) _3] and K(CH(PPh_2NSiMe_3)_2}, whereas the yttrium analogue was obtained from in situ prepared [{CH(PPh _2NSiMe_3)_2}YCI_2]_2 and NaBH_4. All new compounds were char-acterized by standard analytical/spectroscopic techniques, and the solidstate structures were established by single-crystal X-ray diffraction. The ring-opening polymerization (ROP) of ε-caprolactone initiated by [(CH(PPh_2NSiMe _3)_2}La(BH_4)_2(THF)] and [{CH(PPh _2NSiMe_3)_2}Ln(BH_4)_2] (Ln = Y, Lu) was studied. At 0°C the molar mass distributions determined were the narrowest values [M?_w/M?_n= 1.06-1.11) ever obtained for the ROP of ε-caprolactone initiated by rareearth-metal borohydride species. DFT investigations of the reaction mechanism indicate that this type of complex reacts in an unprecedented manner with the first B-H activation being achieved within two steps. This particularity has been attributed to the metallic fragment based on the natural bond order analysis.
机译：已知稀土金属硼氢化物是用于非极性和极性单体聚合的有效催化剂。双硼氢化物[{CH（PPh _2NSiMe_3）_2} La（BH_4）_2（THF）]和[（CH（PPh2N？iMe。，）2} Ln（BH_4）_2]（Ln = Y，Lu）通过[Ln（BH_4）_3（THF）_3]和K（CH（PPh_2NSiMe_3）_2}制备镧和the络合物，而钇类似物则从原位制备[{CH （PPh _2NSiMe_3）_2} YCI_2] _2和NaBH_4。所有新化合物均通过标准分析/光谱技术表征，并通过单晶X射线衍射建立了固态结构。研究了由[[CH（PPh_2NSiMe _3）_2} La（BH_4）_2（THF）]和[{CH（PPh _2NSiMe_3）_2} Ln（BH_4）_2]（Ln = Y，Lu）引发的ε-己内酯。 0°C时确定的摩尔质量分布是稀土金属硼氢化物引发的ε-己内酯的ROP所获得的最窄的值[M？_w / M？_n = 1.06-1.11]，反应机理的DFT研究表明：这种复杂的反应以前所未有的方式在两个步骤中实现了首次B-H激活。这种特殊性归因于基于自然键序分析的金属碎片。

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