Abstract
In order to study crystal packings and hydrogen bonding frameworks, low-temperature X-ray structures were determined for three onium salts of general formula B H+(MeSO2)2N−, where BH+ is acetamidinium (1, monoclinic, space group P21/c, Z = 4), guanidinium (2, monoclinic, P21/c, Z = 4), or 4,6-diamino-2-thioxo-2,3-dihydropyrimidinium (3, monoclinic P21/n, Z = 4). In every case the ions create three-dimensional N − H ∙∙∙ N/O networks, in which all N − H donors of the cations and four (in 1) or five (2, 3) acceptors of the anion are involved; non-conventional secondary bonds, e.g. C − H ∙∙∙ O/N, do not play an important role in the packings. For the isotypic structures 1 and 2, congruencies and dissimilarities of the hydrogen bonding patterns are discussed in detail. Despite the structural and chemical differences between the cations and the way in which they are attached to the anion, each of the three structures displays a robust eight-membered ring synthon [N2 = R2
2(8), antidromic] constructed via two-centre hydrogen bonds from a syn, syn-sequence H − N − C (sp2) −N −H of the respective cation and a V-shaped O − S (sp3) − N fragment of the anion. Although the networks in 2 and 3 contain several N − H (∙∙∙ O)2 three-centre interactions, the two-point connectivity of the synthon is distinctly preserved. The results indicate that the (MeSO2)2N− ion may be utilized in crystal engineering as a dependable building block.
为了研究晶体的堆积和氢键框架,对三种通式为BH
+(MeSO
2)
2N
−的醇盐进行了低温X射线结构测定,其中BH
+分别为乙酰胺盐(1,单斜,空间群P2
1/c,Z = 4)、
胍盐(2,单斜,P2
1/c,Z = 4)或4,6-二
氨基-2-
硫代-2,3-二氢
嘧啶盐(3,单斜P2
1/n,Z = 4)。在每种情况下,离子形成三维N − H ∙∙∙ N/O网络,其中阳离子的所有N − H供体和阴离子的四个(在1中)或五个(2,3)受体参与;非常规的二次键,例如C − H ∙∙∙ O/N,在堆积中并不起重要作用。对于同型结构1和2,详细讨论了氢键模式的一致性和差异性。尽管阳离子之间存在结构和
化学上的差异以及它们与阴离子连接的方式不同,但三种结构都显示出由阳离子的同构同向序列H − N − C(sp
2)−N −H和阴离子的V形O − S(sp
3)−N片段通过双中心氢键构建的稳定的八元环合子[N
2 = R
22(8),反向]。尽管2和3中的网络包含几个N − H (∙∙∙ O)
2三中心相互作用,但合子的双点连接性得到明显保留。结果表明(MeSO
2)
2N
−离子可以作为可靠的构建模块用于晶体工程。