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Ligation-Enhanced π-Hole···π Interactions Involving Isocyanides: Effect of π-Hole···π Noncovalent Bonding on Conformational Stabilization of Acyclic Diaminocarbene Ligands
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2018-05-24 00:00:00 , DOI: 10.1021/acs.inorgchem.8b01027
Alexander S. Mikherdov 1 , Mikhail A. Kinzhalov 1 , Alexander S. Novikov 1 , Vadim P. Boyarskiy 1 , Irina A. Boyarskaya 1 , Margarita S. Avdontceva 1 , Vadim Yu. Kukushkin 1
Affiliation  

The reaction of cis-[PdCl2(CNXyl)2] (Xyl = 2,6-Me2C6H3) with the aminoazoles [1H-imidazol-2-amine (1), 4H-1,2,4-triazol-3-amine (2), 1H-tetrazol-5-amine (3), 1H-benzimidazol-2-amine (4), 1-alkyl-1H-benzimidazol-2-amines, where alkyl = Me (5), Et (6)] in a 2:1 ratio in the presence of a base in CHCl3 at RT proceeds regioselectively and leads to the binuclear diaminocarbene complexes [(ClPdCNXyl)2{μ-C(N-azolyl)N(Xyl)C═NXyl}] (712; 73–91%). Compounds 712 were characterized by C, H, N elemental analyses, high-resolution ESI+-MS, Fourier transform infrared spectroscopy, 1D (1H, 13C) and 2D (1H,1H-COSY, 1H,1H-NOESY, 1H,13C-HSQC, 1H,13C-HMBC) NMR spectroscopies, and X-ray diffraction (XRDn). Inspection of the XRDn data and results of the Hirshfeld surface analysis suggest the presence in all six structures of intramolecular π-holeisocyanide···πarene interactions between the electrophilic C atom of the isocyanide moiety and the neighboring arene ring. These interactions also result in distortion of the Pd–C≡N–Xyl fragment from the linearity. Results of density functional theory calculations [M06/MWB28 (Pd) and 6-31G* (other atoms) level of theory] for model structures of 79 followed by the topological analysis of the electron density distribution within the framework of Bader’s theory (QTAIM method) reveal the presence of these weak interactions also in a CHCl3 solution, and their calculated strength is 1.9–2.2 kcal/mol. The natural bond orbital analysis of 79 revealed that π(C–C)Xyl → π*(C–N)isocyanide charge transfer (CT) takes place along with the intramolecular π-holeisocyanide···πarene interactions. The observed π(C–C)Xyl → π*(C–N)isocyanide CT is due to ligation of the isocyanide to the metal center, whereas in the cases of the uncomplexed p-CNC6H4NC and CNXyl species, the effects of CT are negligible. Available CCDC data were processed from the perspective of isocyanide-involving π-hole···π interactions, disclosed the role of metal coordination in the π-hole donor ability of isocyanides, and verified the π-holeisocyanide···πarene interaction effect on the stabilization of the in-conformation in metal-bound acyclic diaminocarbenes.

中文翻译:

涉及异氰酸酯的增强连接的π-Hole···π相互作用:π-Hole···π非共价键对无环二氨基卡宾配体构象稳定性的影响

的反应顺式- [的PdCl 2(CNXyl)2 ](=的Xyl 2,6-ME 2 ç 6 ħ 3)与aminoazoles [1 ħ咪唑-2-胺(1),4 ħ -1,2, 4-三唑-3-胺(2),1 H-四唑-5-胺(3),1 H-苯并咪唑-2-胺(4),1-烷基-1 H-苯并咪唑-2-胺,其中烷基= Me(5),Et(6)],在碱在CHCl 3中的存在下,以2:1的比例存在在RT和区域选择性引线进入的双核配合物diaminocarbene [(ClPdCNXyl)2 {μ- ÇÑ -azolyl)N(的Xyl)ç ═NXyl}](7 - 12 ; 73-91%)。化合物7 - 12进行了表征为C,H,N元素分析,高分辨率ESI + -MS,傅里叶变换红外光谱法,1D(1 H,13 C)和图2D(1 H,1个H-COSY,1 H,1 H-NOESY,1 H,13 C-HSQC,1 H,13C-HMBC)NMR光谱和X射线衍射(XRDn)。检查XRDn数据和Hirshfeld表面分析的结果表明,异氰酸酯部分的亲电C原子与相邻的芳烃环之间存在分子内π孔异氰酸酯···π芳烃相互作用的所有六个结构。这些相互作用还导致线性关系中的Pd–C≡N–Xyl片段变形。79模型结构的密度泛函理论计算结果[M06 / MWB28(Pd)和6-31G *(其他原子)理论水平],然后在Bader理论框架内对电子密度分布进行拓扑分析( QTAIM方法)揭示了在CHCl中也存在这些弱相互作用3种溶液,其计算强度为1.9–2.2 kcal / mol。79的自然键轨道分析表明,π(CC)Xyl→π*(C–N)异氰酸酯电荷转移(CT)与分子内π孔异氰酸酯···π芳烃相互作用同时发生。观察到的π(C–C)Xyl →π*(C–N)异氰酸酯CT是由于异氰酸酯与金属中心的连接所致,而在未络合的p -CNC 6 H 4情况下NC和CNXyl物种,CT的影响可忽略不计。从涉及异氰酸酯的π-孔···π相互作用的角度处理了可用的CCDC数据,揭示了金属配位在异氰酸酯的π-孔给体能力中的作用,并验证了π-孔异氰酸酯···π芳烃的相互作用上的稳定效果-conformation在金属结合的无环diaminocarbenes。
更新日期:2018-05-24
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