The reactions of iron(III) bromide and iron(II) thiocyanate with ammonia and their reductions with alkali metals in liquid-ammonia solutions of alkali metal cyanides

Abstract Iron(II) thiocyanate dissolves in liquid ammonia to form ammines Fe(NCS) 2 ·8NH 3 , Fe(NCS) 2 ·7NH 3 and Fe(NCS) 3 ·5NH 3 ; these evolve ammonia at room temperature to form the diammine Fe(NCS) 2 (NH 3 ) 2 which has a tetragonal structure with thiocyanate bridges. Iron(III) bromide is also soluble in ammonia but with partial ammonolysis. Reduction of these compounds, and of iron(II) bromide, with potassium or caesium in ammonia solutions of the appropriate alkali metal cyanide yields cyanoferrates(O). Only Cs 4 Fe(CN) 4 has been isolated in a pure state; it is oxidized by ammonium cyanide in ammonia to Cs 4 [Fe(CN) 6 ].