Tolpygin Aleksei O, Glukhova Tatyana A, Cherkasov Anton V, Fukin Georgy K, Aleksanyan Diana V, Cui Dongmei, Trifonov Alexander A
Institute of Organometallic Chemistry of Russian Academy of Sciences, Tropinina 49, GSP-445, 630950, Nizhny Novgorod, Russia.
Dalton Trans. 2015 Oct 7;44(37):16465-74. doi: 10.1039/c5dt02570b.
A new tridentate amidine 2-[Ph2P(O)]C6H4NHC(tBu)[double bond, length as m-dash]N(2,6-Me2C6H3) (1) bearing a side chain pendant Ph2P[double bond, length as m-dash]O group was synthesized and proved to be a suitable ligand for coordination to rare-earths ions. Bis(alkyl) complexes {2-[Ph2P(O)]C6H4NC(tBu)N(2,6-Me2C6H3)}Ln(CH2SiMe3)2(THF)n (Ln = Y, n = 1 (3), Ln = Er, n = 1 (4), Ln = Lu, n = 0 (5)) were prepared using alkane elimination reactions of and Ln(CH2SiMe3)3(THF)2 (Ln = Y, Er, Lu) in hexane and were isolated in 50, 70 and 75% yields respectively. The X-ray studies revealed that complexes 2-5 feature intramolecular coordination of P[double bond, length as m-dash]O groups to metal ions. The lutetium complex 5 proved to be rather stable: at 20 °C its half-life time is 1155 h, while for the yttrium analogue the half-life time was found to be 63 h. Complexes 3-5 were evaluated as precatalysts for isoprene polymerization. The systems Ln/borate/AliBu3 (Ln = 3-5, borate = [PhNHMe2][B(C6F5)4], [Ph3C][B(C6F5)4]) turned out to be highly efficient in isoprene polymerization and enable complete conversion of 1000-10,000 equivalents of monomer into polymer at 20 °C within 0.5-2.5 h affording polyisoprenes with a very high content of 1,4-cis units (up to 96.6%) and from narrow (1.49) to moderate (3.54) polydispersities. A comparative study of catalytic performance of the related bis(alkyl) yttrium complexes supported by amidinate ligands of different denticities and structures tBuC(N-2,6iPr2C6H4)2, tBuC(N-2,6-iPr2C6H4)(N-2-MeOC6H4) and {2-[Ph2P(O)]C6H4NC(tBu)N(2,6-Me2C6H3)}(-) demonstrated that the introduction of a pendant donor group (2-MeOC6H4 or Ph2P(O)) into a side chain of amidinate scaffolds results in a significant increase in catalytic activity. The amidinate ligand bearing a Ph2P(O)-group provides a high isoprene polymerization rate along with excellent control over regio- and stereoselectivities and allows us to obtain polyisoprenes with a reasonable molecular weight distribution.
合成了一种新的三齿脒2-[Ph2P(O)]C6H4NHC(tBu)=N(2,6-Me2C6H3)（1），其带有侧链悬挂的Ph2P=O基团，并且被证明是一种适合与稀土离子配位的配体。通过Ln(CH2SiMe3)3(THF)2（Ln = Y、Er、Lu）在己烷中的烷烃消除反应制备了双（烷基）配合物{2-[Ph2P(O)]C6H4NC(tBu)N(2,6-Me2C6H3)}Ln(CH2SiMe3)2(THF)n（Ln = Y，n = 1（3）；Ln = Er，n = 1（4）；Ln = Lu，n = 0（5）），并分别以50%、70%和75%的产率分离得到。X射线研究表明，配合物2 - 5具有P=O基团与金属离子的分子内配位。镥配合物5被证明相当稳定：在20°C时其半衰期为1155小时，而钇类似物的半衰期为63小时。评估了配合物3 - 5作为异戊二烯聚合的预催化剂。体系Ln/硼酸盐/AliBu3（Ln = 3 - 5，硼酸盐 = [PhNHMe2][B(C_6F_5)_4]、[Ph_3C][B(C_6F_5)_4]）在异戊二烯聚合中表现出高效性，能够在20°C下0.5 - 2.5小时内将1000 - 10,000当量的单体完全转化为聚合物，得到具有非常高的1,4 - 顺式单元含量（高达96.6%）且多分散性从窄（1.49）到中等（3.54）的聚异戊二烯。对由不同齿数和结构的脒基配体tBuC(N - 2,6iPr2C6H4)2、tBuC(N - 2,6 - iPr2C6H4)(N - 2 - MeOC6H4)和{2-[Ph2P(O)]C6H4NC(tBu)N(2,6-Me2C6H3)}(-)支持的相关双（烷基）钇配合物的催化性能进行了比较研究，结果表明在脒基骨架的侧链中引入悬挂供体基团（2 - MeOC6H4或Ph2P(O)）会导致催化活性显著提高。带有Ph2P(O)基团的脒基配体提供了高的异戊二烯聚合速率，同时对区域和立体选择性具有出色的控制，并使我们能够获得具有合理分子量分布的聚异戊二烯。
