N-Heterocyclic carbene adducts of the heavier group 15 tribromides. Normal to abnormal isomerism and bromide ion abstraction,Dalton Transactions

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N-Heterocyclic carbene adducts of the heavier group 15 tribromides. Normal to abnormal isomerism and bromide ion abstraction
Dalton Transactions ( IF 3.5 ) Pub Date : 2017-07-25 00:00:00 , DOI: 10.1039/c7dt02431b
Jordan B. Waters _{1,

2,

3,

4,

5} , Qien Chen _{1,

2,

3,

4,

5} , Thomas A. Everitt _{1,

2,

3,

4,

5} , Jose M. Goicoechea _{1,

2,

3,

4,

5}

Affiliation

The reactivity of the heavier group 15 tribromides, SbBr₃ and BiBr₃, towards 1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene (IPr) is described. These reactions quantitatively afford Lewis acid–base adducts, (IPr)EBr₃ (E = Sb 1; Bi 2), which readily react with AlBr₃ yielding cationic species [(IPr)EBr₂]⁺ (E = Sb 3; Bi 4). Under thermal treatment, the N-heterocyclic carbene ligands in 1 and 2 will readily isomerise to afford the abnormally-bonded (or mesoionic) complexes (aIPr)EBr₃ (E = Sb 5; Bi 6). As with 1 and 2, bromide abstraction from such compounds readily affords the cationic complexes [(aIPr)EBr₂]⁺ (E = Sb 7; Bi 8). Finally, in an effort to elucidate the isomerisation process which allows for the conversion of 1 and 2 to the abnormally bonded systems (compounds 5 and 6), compound 1 was reacted with a further equivalent of IPr to afford the cationic species [(aIPr)₂SbBr₂]⁺ (9). This strongly suggests that the normal to abnormal isomerisation of the N-heterocylic carbene ligands in compounds 1 and 2 is mediated by the presence of free IPr. Compound [9]Br can be used to access the dicationic species [(aIPr)₂SbBr]²⁺ (10), which we have identified spectroscopically. Single crystal X-ray structures and spectroscopic data for all compounds are discussed.

中文翻译：

15个较重的三溴化物的N-杂环卡宾加合物。正常到异常异构现象和溴离子提取

较重的基团的反应15三溴化物，SBBR ₃和BIBR ₃，向1,3-双（2,6-二异丙基） -咪唑-2-亚基（IPR）进行说明。这些反应定量地提供了路易斯酸碱加成物（IPr）EBr ₃（E = Sb 1 ; Bi 2），这些加成物容易与AlBr ₃反应生成阳离子种类[（IPr）EBr ₂ ] ⁺（E = Sb 3 ; Bi 4）。在热处理下，1和2中的N-杂环卡宾配体将容易异构化，以提供异常键合的（或中离子的）配合物（aIPr）EBr ₃（E = Sb5；Bi 6）。与1和2一样，从此类化合物中提取溴化物可轻松提供阳离子络合物[（aIPr）EBr ₂ ] ⁺（E = Sb 7 ; Bi 8）。最后，为了阐明允许1和2转化为异常键合的体系（化合物5和6）的异构化过程，使化合物1与另一当量的IPr反应，得到阳离子种[[aIPr] ₂ SbBr ₂ ] ⁺（9）。这有力地表明，化合物1和2中N-杂环卡宾配体的正常至异常异构化是由游离IPr的存在介导的。化合物[ 9 ] Br可以用于访问我们已经通过光谱法鉴定的专用化合物[ （aIPr）₂ SbBr] ²⁺（10）。讨论了所有化合物的单晶X射线结构和光谱数据。

更新日期：2017-09-20

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