title: Linear chain compound
text: # Linear chain compound
  
  In chemistry and materials science, linear chain compounds are materials composed of one-dimensional arrays of metal-metal bonded molecules or ions. Such materials exhibit anisotropic electrical conductivity.
  
  ## Examples
  
  Most examples are composed of square planar complexes. Thus, upon crystallization, molecules of $Rh(acac)(CO)_2$ stack with Rh···Rh distances of about 326 pm. Classic examples include Krogmann's salt and Magnus's green salt. Another example is the partially oxidized derivatives of $[Pt(oxalate)_2]^{2−}.$ The otherwise ordinary complex $IrBr(CO)_3$ gives an electrically conductive derivative upon oxidation, e.g., with bromine to give $IrBr_{1+x}(CO)_{3−x},$ where x ~0.05. Related chlorides have the formulae $IrCl_{1+x}(CO)_3$ and $K_{0.6}Ir(CO)_2Cl_2·½H_2O.$
  
  In contrast to linear chain compounds, extended metal atom chains (EMACs) are molecules or ions that consist of a finite, often short, linear strings of metal atoms, surrounded by organic ligands.
  
  One group of platinum chains is based on alternating cations and anions of $[Pt(CNR)_4]^{2+}$ (R = iPr, $c-C_{12}H_{23},$ $p-(C_2H_5)C_6H_4)$ and $[Pt(CN)_4]^{2−}.$ These may be able to be used as vapochromic sensor materials, or materials which change color when exposed to different vapors.
  
  Linear chains of Pd-Pd bonds protected by a "π-electron sheath" are known.
  
  Not only do these olefin-stabilized metal chains constitute a significant contribution to the field of organometallic chemistry, both the complex's metal atom structures and the olefin ligands themselves can conduct a current.
  
  ## Methodology
  
  Some linear chain compounds are produced or fabricated by electrocrystallization. The technique is used to obtain single crystals of low-dimensional electrical conductors.
  
  