Convenient synthesis, properties and the structure of tetramethylammonium tris(pyrimidine-2-thiolato)ferrate(II): an iron complex with three stable four-membered N,S-chelate rings

Abstract Reaction of iron(II) chloride with sodium pyrimidine-2-thiolate in ethanol or methanol followed by addition of R 4 NBr affords (R 4 N)[Fe(SC 4 H 3 N 2 ) 3 ] (R = Me, Et) in high yields. (Me 4 N)[Fe(SC 4 H 3 N 2 ) 3 ] crystallizes in the triclinic space group P 1 with a = 7.163(2), b = 10.002(3), c = 15.456(3) A, α = 103.23(1)°, β = 91.25(1)°, γ = 92.09(1)° and Z = 2. The structure was refined to R = 2.9% on the basis of 5663 unique data ( F o 2 >2.5σ( F o 2 )). The octahedral geometry about iron is highly distorted due to the presence of three four-membered chelate rings with an exceptionally small bite angle of ca . 67°. Average FeN and FeS distance are 2.163 and 2.529 A respectively. The complex is isolated as the mer isomer. Mossbauer studies in polycrystalline state together with UVVis and magnetic susceptibility measurement in acetonitrile solution demonstrate that the iron is in +2 oxidation state with a high-spin electronic configuration.