Low-dimensional hydrogen-bonded structures in the 1:1 and 1:2 proton-transfer compounds of 4,5-dichlorophthalic acid with the aliphatic Lewis bases triethylamine, diethylamine, n-butylamine and piperidine

Abstract

The structures of the proton-transfer compounds of 4,5-dichlorophthalic acid (DCPA) with the aliphatic Lewis bases triethylamine, diethylamine, n-butylamine and piperidine, namely triethylaminium 2-carboxy-4,5-dichlorobenzoate, C6H16N+烸H3Cl2O4-, (I), diethylaminium 2-carboxy-4,5-dichlorobenzoate, C4H12N+烸H3Cl2O4-, (II), bis(butanaminium) 4,5-dichlorobenzene-1,2-dicarboxylate monohydrate, 2C4H12N+烸H2Cl2O42-爲O, (III), and bis(piperidinium) 4,5-dichlorobenzene-1,2-dicarboxylate monohydrate, 2C5H12N+烸H2Cl2O42-爲O, (IV), have been determined at 200 K. All compounds have hydrogen-bonding associations, giving discrete cation-anion units in (I) and linear chains in (II), while (III) and (IV) both have two-dimensional structures. In (I), a discrete cation-anion unit is formed through an asymmetric R12(4) N+-HO2 hydrogen-bonding association, whereas in (II), chains are formed through linear N-HO associations involving both aminium H-atom donors. In compounds (III) and (IV), the primary N-HO-linked cation-anion units are extended into a two-dimensional sheet structure via amide-carboxyl N-HO and amide-carbonyl N-HO interactions. In the 1:1 salts (I) and (II), the hydrogen 4,5-dichlorophthalate anions are essentially planar with short intramolecular carboxyl-carboxyl O-HO hydrogen bonds [OO = 2.4223 (14) and 2.388 (2) Ŭ respectively]. This work provides a further example of the uncommon zero-dimensional hydrogen-bonded DCPA-Lewis base salt and the one-dimensional chain structure type, while even with the hydrate structures of the 1:2 salts with the primary and secondary amines, the low dimensionality generally associated with 1:1 DCPA salts is also found.