Application, structure, salts and complexes of lidocaine: a review. Part VIII. Structure of bis(lidocaine) tetrathiocyanatocobaltate(II) monohydrate

The review focuses on application and structure of lidocaine (2-(diethylamino)-N-(2,6-dimethylphenyl)acetamide), its salts and complexes. This part considers the structure of bis(lidocaine) tetrathiocyanatocobaltate(II) monohydrate with the formula (LidH)2[Co(NCS)4] .H2O, which crystallizes in the triclinic centrosymmetric space group P-1 with a = 8.7209(2), b = 11.8438(3), c = 19.9384(5) Å,  = 80.581(2),  = 78.485(2),  = 72.783(2)°, V = 1915.47(8) Å3, Z = 2, Dc = 1.352 Mg/m3. Coordination of the Co2+ ion with thiocyanate ions generates slightly distorted tetrahedral anion Co[(NCS4)]2– with N-bonded thiocyanate groups, while two protonated cations LidH+ and one water molecule remain in an outer coordination sphere. The anion and cations are associated by hydrogen bonds formed by sulfur atoms with an amido nitrogen atom of one cation and with an amino nitrogen atom of another cation; a water molecule is associated with the anion by hydrogen bonds with two sulfur atoms. Classical (N…H–O type) and “non-classical” (C–H…O and C–H…S types) intermolecular hydrogen bonds form planar (relative to cobalt atoms) tetramers united into endless tapes lying along the crystallographic a-axis, while the tapes are united into sheets of the inorganic component of the complex {H2O[Co(NCS)4]2–} lying in planes, making an angle of 52.5° with the crystallographic planes ab; the sheets have a nominal thickness of 15.8 Å and contain cations that are combined into dimers by the R22(10) supramolecular motifs and are structured differently than anions and water molecules.