In this paper we describe monomeric complexes of Pd(II) and Pt(II) with 4,4′,5,5′-tetracyano-2,2′-biimidazole (H2Tcbiim). These compounds always contain the dianion (Tcbiim=) in accord with the greater acidity expected for the cyanosubstituted ring system. The structure of [N(Bu)4]2[Pt(CN)2Tcbiim)] was determined by x-ray crystallography. The composition PtC44H72N12 crystallizes in the P1 triclinic space group with a = 16.664(3) Å, b = 12.422(4) Å, c = 13.842(4) Å, α = 112.47(2), β = 111.01(2), γ = 89.40(2) and Z = 2 molecules/cell. A final agreement or R = 0.038 was obtained for 5359 observed reflections. The structure confirms planar bidentate chelation by Tcbiimu= and an irregular square planar coordination for the platinum atom. The preparation of a series of salts M[Pt(CN)2(Tcbiim)], M = NBu4+, NH4+, Ba2+ and for K+ both the platinum and palladium analogs, are described. The neutral molecule Pt(COD)Tcbiim was also prepared. Activity of these species under oxidation conditions are discussed in relation to the pi accepting properties of the title ligand. © 1984.