As a sequel to prior reports on strong and weak hydrogen bonding in onium di(methanesulfonyl) amide crystals, low-temperature X-ray structures are described for three salts of general formula BH+(MeSO2)2N-, where BH+ is 2,2΄-bipyridinium (1; monoclinic, space group P21/n, Z΄ = 1), 1,10-phenanthrolinium (2; monoclinic, P21/c, Z΄ = 2), or 1,8-bis(dimethylamino) naphthalinium (3; orthorhombic, P212121, Z΄ = 1). Monoprotonation of the organic bases by (MeSO2)2NH results in the formation of an intra-cation N-H···N hydrogen bond, which is asymmetric in 1 and 2, but approximately symmetric in the proton-sponge cation of 3. Moreover, the acidic H atom is engaged in a cation-anion contact N-H···N- in 1 and 2 or H+···Oδ- in 3, thus conferring three-centre character upon the strong hydrogen bonding. Each structure displays a multitude of close interionic C-H···O/N contacts that are geometrically consistent with weak hydrogen bonding. A salient feature is provided by short S-CH2-H···O-S inter-anion contacts, which lead to layers in 1 and to catemers in 2, but are non-existent in structure 3. The cations of both 1 and 2 form π-stacks that are intercalated between the anion layers or surrounded by six anion catemers, whereas in structure 3 each cation is octahedrally coordinated by six anions and vice-versa. The heteroionic connectivity comprises the aforementioned branches of the strong three-centre hydrogen bonds (in 1-3), numerous Car-H···A bonds (1, 2: A = O; 3: A = O, N), S-CH2-H···Nring interactions (1, 2), and close N-CH2-H···O=S contacts (3; possibly destabilizing).
1,8-Bis(dimethylamino)naphthyl-2-ketimines: Inside vs outside protonation