Lithium Complexes with Bridging and Terminal NHC Ligands: The Decisive Influence of an Anionic Tether
Lithium Complexes with Bridging and Terminal NHC Ligands: The Decisive Influence of an Anionic Tether
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DOI：
10.1002/ejic.201901003
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发表时间：
2019-12-02
影响因子：
2.3
通讯作者：
Mansell, Stephen M.
中科院分区：
文献类型：
--
作者：
Evans, Kieren J.;Campbell, Cameron L.;Mansell, Stephen M.
芴基咪唑啉盐[9-（C13 H9）C2 H4 N（CH）C2 H4 N（2，4，6-Me 3C 6 H2）][BF 4]的去质子化得到螺环化合物，该螺环化合物与LiPh/LiN（SiMe 3）（2）或LinBu/LiN（SiMe 3）（2）的协同混合物反应得到包含桥接N（SiMe 3）（2）配体的双锂配合物。相比之下，咪唑鎓盐[9-（C13 H9）C2 H4 N（CH）C2 H2 N（Me）][Br]的去质子化反而产生游离的NHC，其与nBuLi反应形成二聚的NHC桥接的二锂配合物。LiN（SiMe 3）（2）的加入导致配位并形成具有桥接N（SiMe 3）（2）配体的二锂络合物，其特征在于在固态下为一维配位聚合物。1，3-二（2，6-二异丙基苯基）-4，5-二氢咪唑-2-亚基（SIPr）与茚化锂和芴化锂反应，得到可溶性物种，其末端NHC与锂阳离子结合，茚基或芴基与η（5）配位。因此，只有在没有额外的酰胺配体存在的情况下，才观察到NHC供体的对称桥接模式。
Deprotonation of the fluorenyl-tethered imidazolinium salt [9-(C13H9)C2H4N(CH)C2H4N(2,4,6-Me3C6H2)][BF4] gave a spirocyclic compound that reacted with a synergic mixture of LiPh/LiN(SiMe3)(2) or LinBu/LiN(SiMe3)(2) to give a dilithium complex incorporating a bridging N(SiMe3)(2) ligand. In contrast, deprotonation of the imidazolium salt [9-(C13H9)C2H4N(CH)C2H2N(Me)][Br] instead yielded the free NHC, which reacted with nBuLi to form a dimeric, NHC-bridged dilithium complex. Addition of LiN(SiMe3)(2) led to coordination and the formation of a dilithium complex with a bridging N(SiMe3)(2) ligand, which was characterised in the solid state as a 1D coordination polymer. The reaction of 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene (SIPr) with lithium indenide and lithium fluorenide gave soluble species with terminal binding of the NHC to the lithium cation and eta(5) coordination of indenyl or fluorenyl. A symmetrical bridging mode for an NHC donor was therefore observed only if a tethered fluorenyl anion was present with no additional amide ligand.