Daniel Ballarín Ferrer

Hexaaquanickel diorotate(1-) dihydrate at 150 K.

In hexaaquanickel bis(2,6-dioxo-1,2,3,6-tetrahydropyrimidine-4-carboxylate) dihydrate, [Ni(H(2)O)(6)](C(5)H(3)N(2)O(4))(2).2H(2)O, the nickel cation is coordinated by six aqua ligands and only associated with the two orotate ions through hydrogen bonds. The structure is isotypic with the magnesium and zinc analogues. The metal cation sits on a crystallographic center of inversion that relates the water molecules and the organic anions. The orotate moieties form an unbonded one-dimensional chain mediated by a hydrogen-bonded self-recognition interaction. The hexaaquanickel complex molecules bridge these chains laterally, acting as molecular clamps that bring neighboring layers nearer than expected. As a result of this three-dimensional arrangement, a short contact of 3.166 (5) A is observed between two C atoms of two adjacent ribbons.

Using the crystal to engineer the molecule: cis-trans-isomer selection in anionic bis(orotate) complexes

Two chelating orotate2− ligands have been coordinated to the same metal ion, producing the first dianionic bis-orotate complex, [Ni(orotate)2(H2O)2]2−, whose geometric isomer can be selected by enabling or vitiating the formation of non-covalent interactions in the solid in which the product is isolated. This provides an important example of the influence and potential use of non-covalent interactions for isomer selection in the synthesis of coordination compounds, as well as the manner in which such stereochemical selection can be achieved by the appropriate use of counterions.