Kumar Anuj, Yuan Dan, Huynh Han Vinh
Department of Chemistry , National University of Singapore , 3 Science Drive 3 , Singapore 117543.
Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Dushu Lake Campus , Soochow University , Suzhou 215123 , People's Republic of China.
Inorg Chem. 2019 Jun 3;58(11):7545-7553. doi: 10.1021/acs.inorgchem.9b00786. Epub 2019 May 10.
Heterobis(carbene) complexes of palladium(II) and gold(I) containing expanded-ring N-heterocyclic carbenes (erNHCs) have been prepared in order to study their electronic properties. erNHCs with mesityl substituents were found to exhibit anisotropic interferences, which hampered ranking of their donicities by C NMR spectroscopy. The anisotropy effects were found to be stronger in the linear gold complexes, where a smaller coordination number allows the wingtips to spread out more. erNHCs with flexible N-benzyl groups are more suitable, and their donor strengths were found to gradually increase from five- to seven-membered heterocycles. The same trend can also be obtained by comparing the J(C-H) coupling constants of the respective salts, although significant differences between seven- and eight-membered erNHCs could not be detected. The % V values of erNHCs obtained from structures of their palladium and gold complexes revealed that the anisotropic interferences increase with overall steric bulk.
为了研究其电子性质，已制备了含扩环N-杂环卡宾（erNHCs）的钯（II）和金（I）的异双（卡宾）配合物。发现带有均三甲苯基取代基的erNHCs表现出各向异性干扰，这妨碍了通过碳核磁共振光谱对其给电子能力进行排序。在线性金配合物中，各向异性效应更强，因为较小的配位数使翼尖能够更展开。带有柔性N-苄基的erNHCs更合适，并且发现它们的给体强度从五元到七元杂环逐渐增加。通过比较相应盐的J(C-H)耦合常数也可以得到相同的趋势，尽管未检测到七元和八元erNHCs之间的显著差异。从其钯和金配合物的结构获得的erNHCs的%V值表明，各向异性干扰随着整体空间体积的增加而增加。
