A family of six acyclic bis-bidentate Schiff base ligands, L^x (prepared by condensation of 3,6-diformylpyridazine with a range of anilines: 2,4-dimethylaniline L^o,p-Me; 3,5-dichloroaniline L^m,m-Cl; 3,5-difluoroaniline L^m,m-F; p-toluidine L^p-Me; 4-aminophenol L^p-OH; 2,4,6-trimethylaniline L^o,o,p-Me), was complexed, 1:1, with cobalt(ii) or nickel(ii) perchlorate or tetrafluoroborate in refluxing dry acetonitrile. A family of dinuclear, doubly pyridazine-bridged complexes, M₂^II(L^x)₂(solvent)_n(ClO₄)₄ and [Ni₂(L^o,o,p-Me)₂(2H₂O)₄](BF₄)₄, resulted. An X-ray crystal structure determination on [Co₂^II(L^o,o,p)₂(H₂O)₂(MeCN)₂](ClO₄)₄·MeCN confirmed that it has the expected side-by-side architecture with axial solvent molecules completing the octahedral coordination sphere of the two cobalt(ii) ions. Magnetic analysis showed that the pyridazine bridges mediate weak-to-medium antiferromagnetic interactions between the metal ions. Specifically, for the cobalt(ii) complexes J was in the range –12 to –6 cm^–1, while for the nickel(ii) complexes J was in the range –22 to –17 cm^–1. There is no clear cut correlation of J values with electron-donating or -attracting properties of ligand substituent peripheral groups, although it is noted that the smallest J occurs in both the NiNi and CoCo families for the ligand L^o,o,p-Me.