The Synthesis, Structure, Electrical Conduction Properties, and Theory of Divalent, Tetravalent, and One-Dimensional Partially Oxidized Tetracyanoplatinate Complexes

The most novel features of partially oxidized tetracyanoplatinate (POTCP) complexes containing platinum atoms in a nonintegral oxidation state are their highly anisotropic physical properties. The structural basis for these properties is the stacking of square-planar tetracyanoplatinate, “TCP” = [Pt(CN)4], groups, 1, as illustrated in Figure 1. While many square-planar TCP salts of Pt2.0+ are known which form columnar stacks containing infinite chains of Pt atoms, e.g., Rb2[Pt(CN)4] · 1.5H2O, (intrachain Pt-Pt separation, d Pt-Pt is 3.42 Å), 13 striking changes in these complexes can occur if the intrachain separation is ~ 3.0 Å or less (d Pt-Pt in Pt metal = 2.78 Å).66 These changes include the appearance of salts with brilliant metallic lusters ranging from copper to bronze to gold and the onset of quasi-one-dimensional (1-D) metallic conductivity. These properties arise from electron delocalization along the overlapped Pt 5d z2 orbitals (Figure 1) Measurements of the electrical conductivity parallel to the Pt chain reveal values which may be 105 greater than the conductivity perpendicular to the chain direction.