Diruthenium tetracarbonate trianion, [Ru(II/III)(2)(O(2)CO)(4)](3-), based molecule-based magnets: three-dimensional network structure and two-dimensional magnetic ordering.

H(x)K(1-x)M(II)Ru(2)(CO(3))(4)(y)(MeOH)(z) (M = Mn, Fe, Co, Ni, Mg) were synthesized from the reaction of M(II) and K(3)[Ru(2)(CO(3))(4)] in water and are isomorphous with an orthorhombic three-dimensional network structures based on mu(3)-CO(3)(2-) linkages to Ru(2) moieties forming layers and also to trans-M(II)(OH(2))(4) sites forming linked chains that connect the layers. They, as well as non-isomorphous M = Cu, magnetically order as canted ferrimagnets with T(c) = 4.4 +/- 1.0 K. The presence of S = 0 M(II) = Mg(II) has essentially no effect on T(c) suggesting that the main magnetic pathway does not occur the through M(II)-based chains, but only via Ru(2)...Ru(2) linkages that reside in layers. This is a rare example of a magnet based upon a second row transition metal.