A series of three-dimensional (3D) octacyanometallate-based bimetallic magnets, {[Mn(H2O)][Mn-0.75(HCOO)(0.5)(H2O)(0.5)]-[W(CN)(8)]center dot H2O}(4n) (1), {[Mn-2(HCOO)(HCOOH)][M(CN)(8)]center dot H2O}, (M = W (2) and Mo (3)), and {[Mn-2(HCOO)(HCOOH)]-[W(CN)(8)]center dot CH3OH}(n) (M = W (4) and Mo (5)), were synthesized by the reaction of octacyanometallates A(3)[M(CN)(8)]center dot nH(2)O (A = Na, Cs, and (C4H9)(3)NH; M = Wand Mo; and n=2 or 4) with manganese salt (Mn(CH3COO)(2)center dot 4H(2)O, Mn(CIO4)(2)center dot 6H(2)O, and MnCl2 center dot 4H(2)O) in aqueous or methanolic solution containing formic acid. All complexes crystallize in the tetragonal or orthorhombic system. Complex 1 shows an unexpected 3D network structure by connections of manganese ions and octacyanotangstate-manganese double layers via cyanide bridges, while other complexes have typical structure constructions similar to the reported complexes {[MnL](m)(CN)(8)]}, (L = CH3COO-, Cl-, and H2O), which the CN group of [W-v(CN)(8)] coordinates to eight Mn-II ions forming a -[W(CN)(8)]-Mn-4-[W(CN)(8)]-Mn-4- columnar chain, and then all chains share Mn-II ions as the nodes interlocking with each other to form the 3D networks. Magnetic studies indicate that the cyanide group mediates the antiferromagnetic coupling between octacyanometallates and manganese ions in all complexes, and the ferrimagnetic phase transition temperatures are 53, 52, 42, 49, and 41 K for 1-5, respectively.