Arene complexes of beta-diketiminato supported organoscandium cations: mechanism of arene exchange and alkyne insertion in solvent separated ion pairs.
Arene complexes of beta-diketiminato supported organoscandium cations: mechanism of arene exchange and alkyne insertion in solvent separated ion pairs.
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DOI：
10.1002/chem.200601087
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发表时间：
2007-03
期刊：
影响因子：
--
通讯作者：
Paul G. Hayes;W. Piers;M. Parvez
中科院分区：
文献类型：
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作者：
Paul G. Hayes;W. Piers;M. Parvez
通过LMeScR_2与[CPh_3][B（C_6 F_5）_4]在芳烃溶剂中的反应，合成了一类由β-二酮亚胺配体（Ar）NC（CH_3）CHC（CH_3）N（Ar）（Ar= 2，6-iPr-C_6 H_3，LMe）稳定的可分离的有机钪阳离子。芳烃如溴苯、苯、甲苯、对二甲苯和均三甲苯以η 6-键合模式结合钪中心，产生阳离子la-e。它们的溶液和固态结构已被探索使用多核NMR光谱和X射线晶体学。芳烃交换反应和二苯基乙炔的插入的机理研究表明，这些过程发生通过芳烃中间体的较低的hapticity，随后由传入的试剂的结合。这两个步骤中的哪一个是速率限制取决于被置换的芳烃和/或进入的底物的性质。实验提出了一个统一的观点，这些机制，这与传播过程中的烯烃聚合介导的阳离子。
A family of isolable solvent separated organoscandium methyl cations stabilized by beta-diketiminato ligands (Ar)NC(CH3)CHC(CH3)N(Ar) (Ar=2,6-iPr-C6H3, LMe) has been prepared by reaction of LMeScR2 with [CPh3][B(C6F5)4] in the presence of an arene solvent. Arenes such as bromobenzene, benzene, toluene, para-xylene and mesitylene bind the scandium center in an eta6-bonding mode, yielding cations 1 a-e. Their solution and solid-state structures have been explored using multinuclear NMR spectroscopy and X-ray crystallography. Mechanistic studies on arene exchange reactions and the insertion of diphenylacetylene indicate that these processes occur via arene intermediates of lower hapticity, followed by binding of the incoming reagent. Which of the two steps is rate limiting depends on the arene being displaced and/or the nature of the incoming substrate. The experiments present a unified view of these mechanisms, which have relevance to propagation processes in olefin polymerizations mediated by such cations.