The crystal and molecular structure of sodium pentacyanoammineferrate(II) heptahydrate. Role of intermolecular hydrogen-bond interactions

The crystal and molecular structures of sodium pentacyanoammineferrate(II) heptahydrate have been determined by X-ray diffraction. The Fe-N distance i s longer than in the analogous iron(III) complex by 0.06 Angstrom; the Fe-C and C-N distances are similar to those for the hexacyanoferrate(II) specie s, although with a significant relative shortening of the trans Fe-C bonds. The anions display a chain-like arrangement, with interlinking sodium ions and water molecules H-bonded to cyanide N atoms. By comparing with related structures of pentacyano-L-ferrate(II) ions (L = NO+, CN-), it results tha t the binding mode of the L ligand influences strongly both the first- and second-sphere metal-ligand interactions. (C) 2001 Elsevier Science B.V. All rights reserved.