Smith Graham, Wermuth Urs D, White Jonathan M
School of Physical and Chemical Sciences, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia.
Acta Crystallogr C. 2009 Mar;65(Pt 3):o103-7. doi: 10.1107/S0108270109004405. Epub 2009 Feb 21.
The structures of the anhydrous 1:1 proton-transfer compounds of 4,5-dichlorophthalic acid (DCPA) with the monocyclic heteroaromatic Lewis bases 2-aminopyrimidine, 3-(aminocarbonyl)pyridine (nicotinamide) and 4-(aminocarbonyl)pyridine (isonicotinamide), namely 2-aminopyrimidinium 2-carboxy-4,5-dichlorobenzoate, C(4)H(6)N(3)(+).C(8)H(3)Cl(2)O(4)(-), (I), 3-(aminocarbonyl)pyridinium 2-carboxy-4,5-dichlorobenzoate, C(6)H(7)N(2)O(+).C(8)H(3)Cl(2)O(4)(-), (II), and the unusual salt adduct 4-(aminocarbonyl)pyridinium 2-carboxy-4,5-dichlorobenzoate-methyl 2-carboxy-4,5-dichlorobenzoate (1/1), C(6)H(7)N(2)O(+).C(8)H(3)Cl(2)O(4)(-).C(9)H(6)Cl(2)O(4), (III), have been determined at 130 K. Compound (I) forms discrete centrosymmetric hydrogen-bonded cyclic bis(cation-anion) units having both R(2)(2)(8) and R(1)(2)(4) N-H...O interactions. In (II), the primary N-H...O-linked cation-anion units are extended into a two-dimensional sheet structure via amide-carboxyl and amide-carbonyl N-H...O interactions. The structure of (III) reveals the presence of an unusual and unexpected self-synthesized methyl monoester of the acid as an adduct molecule, giving one-dimensional hydrogen-bonded chains. In all three structures, the hydrogen phthalate anions are essentially planar with short intramolecular carboxyl-carboxylate O-H...O hydrogen bonds [O...O = 2.393 (8)-2.410 (2) A]. This work provides examples of low-dimensional 1:1 hydrogen-bonded DCPA structure types, and includes the first example of a discrete cyclic ;heterotetramer.' This low dimensionality in the structures of the 1:1 aromatic Lewis base salts of the parent acid is generally associated with the planar DCPA anion species.
4,5-二氯邻苯二甲酸（DCPA）与单环杂芳族路易斯碱2-氨基嘧啶、3-（氨基羰基）吡啶（烟酰胺）和4-（氨基羰基）吡啶（异烟酰胺）形成的无水1:1质子转移化合物的结构，即2-氨基嘧啶鎓2-羧基-4,5-二氯苯甲酸盐，C(4)H(6)N(3)(+)·C(8)H(3)Cl(2)O(4)(-)，（I），3-（氨基羰基）吡啶鎓2-羧基-4,5-二氯苯甲酸盐，C(6)H(7)N(2)O(+)·C(8)H(3)Cl(2)O(4)(-)，（II），以及不寻常的盐加合物4-（氨基羰基）吡啶鎓2-羧基-4,5-二氯苯甲酸盐-甲基2-羧基-4,5-二氯苯甲酸盐（1/1），C(6)H(7)N(2)O(+)·C(8)H(3)Cl(2)O(4)(-)·C(9)H(6)Cl(2)O(4)，（III），已在130 K下测定。化合物（I）形成离散的中心对称氢键连接的环状双（阳离子-阴离子）单元，同时具有R(2)(2)(8)和R(1)(2)(4) N-H...O相互作用。在（II）中，主要的N-H...O连接的阳离子-阴离子单元通过酰胺-羧基和酰胺-羰基N-H...O相互作用扩展成二维片状结构。（III）的结构揭示了存在一种不寻常且意想不到的该酸的自合成甲基单酯作为加合物分子，形成一维氢键链。在所有三种结构中，邻苯二甲酸氢根阴离子基本呈平面状，具有短的分子内羧基-羧酸盐O-H...O氢键[O...O = 2.393 (8)-2.410 (2) Å]。这项工作提供了低维1:1氢键连接的DCPA结构类型的实例，包括离散环状“杂四聚体”的第一个实例。母体酸的1:1芳香族路易斯碱盐结构中的这种低维性通常与平面DCPA阴离子物种有关。
