Tamm Matthias, Petrovic Dejan, Randoll Sören, Beer Stephan, Bannenberg Thomas, Jones Peter G, Grunenberg Jörg
Institut für Anorganische und Analytische Chemie, Technische Universität Carolo-Wilhelmina zu Braunschweig, Hagenring 30, D-38106 Braunschweig, Germany.
Org Biomol Chem. 2007 Feb 7;5(3):523-30. doi: 10.1039/b615418b. Epub 2007 Jan 4.
The preparation of 2-iminoimidazolines - has been accomplished by the Staudinger reaction of the carbenes 1,3-di-tert-butylimidazolin-2-ylidene (), 1,3-diisopropyl-4,5-dimethylimidazolin-2-ylidene (), 1,3-diisopropylimidazolin-2-ylidene (), 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (), 1,3-bis(2,6-diisopropylphenylimidazolin-2-ylidene () and 1,3,4,5-tetramethylimidazolin-2-ylidene () with trimethylsilyl azide (Me3SiN3) followed by desilylation of the resulting 2-trimethylsilyliminoimidazolines -. The X-ray crystal structures of and have been established, revealing C1-N1-Si1 angles that are more obtuse than the corresponding P-N-Si angles observed in related trimethylsilyl iminophosphoranes. Together with , the disilylated side product 1,3-diisopropyl-2-(trimethylsilylimino)-4-trimethylsilylimidazoline () has been isolated and structurally characterized. Cleavage of the N-Si bonds in and formation of is easily achieved by stirring in methanol. The molecular structures of the 2-iminoimidazolines are reported, indicating that the structural parameters are best described by non-ylidic resonance structures and that electron delocalization within the imidazole heterocycle does not play a crucial role in these imine systems. Compound forms a head-to-head dimer in the solid state via weak intermolecular N-H...N contacts, which have additionally been characterized by means of compliance constants. To further analyze the electronic structure of these imines in comparison to related guanidine ligands, the proton affinities (PAs) of the model compounds 2-imino-1,3-dimethylimidazoline (), 2-imino-1,3-dimethylimidazolidine () and tetramethylguanidine () have been calculated by means of density functional theory. Finally, the charge distribution in - and the relative contribution of relevant resonance structures have been determined using natural bond orbitals (NBO) and natural resonance theory (NRT).
2-亚氨基咪唑啉的制备——是通过卡宾1,3-二叔丁基咪唑啉-2-亚基（）、1,3-二异丙基-4,5-二甲基咪唑啉-2-亚基（）、1,3-二异丙基咪唑啉-2-亚基（）、1,3-双（2,4,6-三甲基苯基）咪唑啉-2-亚基（）、1,3-双（2,6-二异丙基苯基）咪唑啉-2-亚基（）和1,3,4,5-四甲基咪唑啉-2-亚基（）与三甲基硅基叠氮化物（Me3SiN3）发生施陶丁格反应，随后对生成的2-三甲基硅基亚氨基咪唑啉-进行脱硅反应来实现的。已确定了和的X射线晶体结构，结果表明C1-N1-Si1角比在相关三甲基硅基亚氨基磷烷中观察到的相应P-N-Si角更钝。与一起，分离出了二硅化副产物1,3-二异丙基-2-（三甲基硅基亚氨基）-4-三甲基硅基咪唑啉（）并对其进行了结构表征。通过在甲醇中搅拌可轻松实现和中N-Si键的断裂并形成。报道了2-亚氨基咪唑啉的分子结构，表明结构参数最好用非叶立德共振结构来描述，并且咪唑杂环内的电子离域在这些亚胺体系中并不起关键作用。化合物在固态下通过弱分子间N-H...N接触形成头对头二聚体，此外还通过柔顺常数对其进行了表征。为了与相关胍配体相比进一步分析这些亚胺的电子结构，通过密度泛函理论计算了模型化合物2-亚氨基-1,3-二甲基咪唑啉（）、2-亚氨基-1,3-二甲基咪唑烷（）和四甲基胍（）的质子亲和势（PAs）。最后，使用自然键轨道（NBO）和自然共振理论（NRT）确定了-中的电荷分布以及相关共振结构的相对贡献。
