Strong and weak hydrogen-bonding interactions in the structures of N,N ',N ''-trisubstituted guanidinium chlorides and bromides

The reaction of two trisubstituted guanidines N,N',N- triisopropylguanidine (TPG) and N,N'-diisopropyl-N-2,6-dimethylphenylguanidine (DPArG) with HX or equivalents (X = Cl, Br) yielded the anticipated guanidinium halide salts. The structures of TPGH(+)X(-) (X = Cl, 1), TPGH(+)X(-.)H(2)O (X = Br, 3(.)H(2)O), and DPArGH(+)X(-) (X = Cl, 2; Br, 4) were determined by single-crystal X-ray diffraction analysis to examine the potential intermolecular interactions in these compounds and their influence on the extended structures that were observed. The formation of strong, charge-assisted hydrogen bonds, NH+...X-, dominates the extended structures. In addition, weaker interactions between the N-substituents and between the X- anions and CH bonds of the substituents have an apparent role in the structures of these materials. While the TPGH(+) cation displayed a C-3 propeller-type orientation in the structures of 1 and 3(.)H(2)O, two different isomeric forms for the less symmetric DPArGH(+) cations were observed, and the identity of the anion and of the substituents both appear to be important in determining which form is obtained. Although the DPArGH(+) cation exhibited different isomeric structures in 2 and 4, a common structural motif consisting of hydrogen-bonded chains was observed in their solid-state structures.