Hydrogen-bonded neutral and anionic lamellar networks: Crystal structures of bis(O,O′,O″-hydroorotato)disilver(i) dihydrate, potassium hydroorotate and rubidium hydroorotate. Ab initio calculations on orotic acid and the hydroorotate anion

Abstract

The complex adducts of silver(I) (1), potassium(I) (2) and rubidium(I) (3) with the hydroorotate (2,6-dioxo-1,2,3,6-tetrahydropyrimidine-4-carboxylate) anion have been prepared, and their structures determined by X-ray diffraction. Crystals of bis(O,O′,O″-hydroorotato)disilver(I) dihydrate (1) consist of a polymeric structure which is based on bis(hydroorotato-O,O′) bridged dimers, analogous to those found in many O,O′-bridged silver carboxylates. Extensive hydrogen-bonding and secondary carbonyl-O⋯Ag interactions result in infinite, neutral sheets with an interplanar spacing of 3.085 Å. Crystals of 2 (KC₅H₃N₂O₄) consist of a lamellar structure with infinite anionic sheets parallel to the crystallographic (100) plane. The distance between two adjacent sheets is 3.417 Å and the K⁺ cations are situated between the sheets with slightly distorted square antiprismatic geometries. Compound 3 (RbC₅H₃N₂O₄) is essentially isostructural with the potassium analogue with the interplanar spacing increased to 3.600 Å. Ab initio calculations on orotic acid and the hydroorotate anion were performed. The optimized geometries and harmonic vibrational frequencies were computed using density functional theory B3LYP/6-31G(d) model chemistry. ¹H and ¹³C NMR chemical shifts were calculated at the HF/6-311++(2d,2p) and B3LYP/6-311++G(2d,2p) levels, and compared with experimental values.