Tetraaquabis(hydrogen maleato)zinc(II) by neutron diffraction and tetraaquabis(hydrogen maleato)nickel(II) by high-order X-ray diffraction

Experimental charge density and topological analysis of tetraaquabis(hydrogenmaleato)nickel(II): a comparison with Hirshfeld atom refinement

Experimental charge density analysis is conducted on the coordination compound tetraaquabis(hydrogenmaleato)nickel(II), which exhibits a short intramolecular hydrogen bond. Through topological analysis, the nature of Ni-O bonds is concluded to be intermediate between ionic and covalent, but mainly presenting an ionic character, while the short hydrogen bond is classified as covalent in nature. The compound was also analysed after Hirshfeld atom refinement performed using NoSpherA2. A topological analysis was conducted on the molecular wavefunction and the results are compared with those obtained from experiment. In general, there is good agreement between the refinements, and the chemical bonds involving H atoms are in better agreement with what is expected from neutron data after HAR than they are after multipole refinement.

Actual Symmetry of Symmetric Molecular Adducts in the Gas Phase, Solution and in the Solid State

This review discusses molecular adducts, whose composition allows a symmetric structure. Such adducts are popular model systems, as they are useful for analyzing the effect of structure on the property selected for study since they allow one to reduce the number of parameters. The main objectives of this discussion are to evaluate the influence of the surroundings on the symmetry of these adducts, steric hindrances within the adducts, competition between different noncovalent interactions responsible for stabilizing the adducts, and experimental methods that can be used to study the symmetry at different time scales. This review considers the following central binding units: hydrogen (proton), halogen (anion), metal (cation), water (hydrogen peroxide).

The crucial role of water in shaping low-barrier hydrogen bonds

Low-barrier hydrogen bonds (LBHBs) are key components in a range of chemical processes, often appearing in metal-mediated catalytic applications.

Bis(2,2'-bipyridine-κN,N')(maleato-κO,O)nickel(II) 7.34-hydrate

The title compound, [Ni(C(4)H(2)O(4))(C(10)H(8)N(2))(2)]·7.34H(2)O, was obtained by crystallization from an aqueous ethano-lic reaction mixture containing nickel(II) acetate, maleic acid, bipyridine, sodium hydroxide and ammonia. The asymmetric unit contains one independent complex mol-ecule and 7.34 water mol-ecules occupying eight crystallographically independent positions. Two of these water molecules are disordered. The nickel(II) atom is coordinated in a distorted octa-hedral geometry by two O atoms from one carboxyl-ate group of the maleato ligand and by four N atoms from two 2,2'-bipyridine (bipy) ligands. The water mol-ecules, along with the O atoms of the uncoordinated carboxyl-ate group, form an extended hydro-philic three-dimensional hydrogen-bonded system with large cavities in which the hydro-phobic bipy ligands are located. One H atom of the maleate ligand is involved in a weak hydrogen bond of the C-H⋯O type. Stacking inter-actions between the pyridyl rings of the bipy ligands [centroid-centroid distance = 3.549 (15) Å] lead to the formation of pairs of complex mol-ecules.