Hydrogen bonding influences on the properties of heavily hydrated chloride salts of iron(ii) and ruthenium(ii) complexes of 2,6-bis(pyrazol-3-yl)pyridine, 2,6-bis(1,2,4-triazol-3-yl)pyridine and 2,2′∶6′,2″-terpyridine

The structures of a series of hydrated complex chlorides [Fe(btp)2]Cl2·6H2O, [M(bpp)2]Cl2·6.5H2O (M = Fe, Ru) and [Ru(terpy)2]Cl2·6H2O are described (btp = 2,6-bis(1,2,4-triazol-3-yl)pyridine; bpp = 2,6-bis(pyrazol-3-yl)pyridine; terpy = 2,2′∶6′,2″-terpyridine). The ligands are all of the terimine type. [Fe(btp)2]Cl2·6H2O is high spin while [Fe(bpp)2]Cl2·6.5H2O is low spin, the difference in the average Fe–N distance in the two complexes being 0.24 Å. In all four complex salts there is extensive hydrogen bonding between the water and chloride ions. In addition, for the pyrazolyl and triazolyl ligands this involves the uncoordinated >NH groups. The arrangement of the cations in the four lattices is discussed in terms of the previously described “terpy embrace” adopted widely by bis(terimine)metal systems.