More insight into the crystal structure of [Co(H₂O)₄(4-nba)₂]·2H₂O (4-nba=para-nitrobenzoate): an unprecedented hydrogen bonded Supramolecular network

Abstract

The title complex tetra-aquobis(para-nitrobenzoato)cobalt(II) dihydrate 1 crystallizes in the triclinic space group P ⌈ with the following unit cell dimensions for C₁₄H₂₀N₂CoO₁₄ (M=499.25) a=7.227(5) Å, b=7.341(5) Å, c=10.604(5) Å, α = 85.884(5)^o β = 87.938(5)^o g = 60.178(5) ^o V = 486.8(5) Å3, Z=1, Dc=1.703 g.cm^-3. In 1, the para-nitrobenzoate anion functions as a monodentate ligand and the Co(II) metal is located on a centre of inversion. The central metal is bound by four oxygen atoms of four water ligands, which lie on a square plane and two monodentate nitrobenzoate ligands, which are trans to each other, complete a distorted octahedron around cobalt. The oxygen atom of the nitro group of the para-nitrobenzoate forms hydrogen bonds (H acceptor bonds) with a H atom of the coordinated water on an adjacent Co thus linking the complex in a chain. These chains are further linked by hydrogen bonding which use the crystal water. This gives rise to an unprecedented hydrogen bonded supramolecular network. The title complex can be fully dehydrated to the corresponding anhydrous complex, which in turn can be rehydrated to 1. The synthesis, spectroscopic, thermal and X-ray structural characterization of the title complex 1 are described.