Four C-substituted derivatives of ortho-carborane, 1-R-1,2-C2B10H11, where R = 2â²-pyridyl (1), 2â²-picolyl (2), 5â²-bromo-2â²-pyridyl (3) or 3â²-pyridyl (4) have been prepared using adaptations of standard procedures, and structurally characterised by single crystal X-ray diffraction studies in an exploration of CâHâ¯N hydrogen bonding effects involving their carborane CH units. Calculations at the MP2/6-31G* level of theory were used to assess the strength of the hydrogen bonding detected, and calculated NMR shifts at the GIAO-B3LYP/6-311G* level were compared with measured CâH shifts to show that intramolecular CâHâ¯N hydrogen bonding persisted in solution in the case of compound 1. The value of IR CâH stretching frequencies for probing hydrogen bonding in these systems was also studied. An unsuccessful attempt to convert compound 3 into a macrocyclic species (C2B10H10C5H3N)3 in which three ortho-carborane units are linked through 2,5-disubstituted pyridine rings is also described.
我们采用标准程序的改良方法制备了 1-R-1,2-C2B10H11 四种 C 取代的正
硼烷衍
生物,其中 R = 2â²-
吡啶基 (1)、2â²-
吡啶基 (2)、5â²-
溴-2â²-
吡啶基 (3) 或 3â²-
吡啶基 (4),并通过单晶 X 射线衍射研究对其进行了结构表征,以探索涉及
硼烷 CH 单元的 CâHâ¯N 氢键效应。在 MP2/6-31G* 理论
水平上进行的计算用于评估检测到的氢键强度,在 GIAO-B3LYP/6-311G*
水平上进行的核磁共振位移计算与测量到的 CâH 位移进行了比较,结果表明,在化合物 1 的情况下,分子内 CâHâ¯N 氢键在溶液中持续存在。 此外,还研究了红外 CâH 伸展频率在这些体系中探测氢键的价值。此外,还介绍了将化合物 3 转化为大环化合物 (C2B10H10C5H3N)3 的一次失败尝试,在该大环化合物中,三个正
硼烷单元通过 2,5 二
甲基吡啶环相连。