Tetra-, penta-, and hexacoordination in iron (II) adducts of aliphatic bidentate amines. Crystal and molecular structure of the mononuclear complexes Fe(dienMe)Cl2 and Fe(tmeda)I2

The thf adduct of FeCl₂, FeCl₂(thf)_1.5, reacts with bidentate aliphatic nitrogen bases in toluene as medium to give the corresponding adducts of FeCl₂. X-ray crystallography of Fe(dienMe)Cl₂ (dienMe = bis(2-dimethylaminoethyl)methylamine) has shown the compound to be mononuclear with pentacoordinated iron, thus confirming an earlier suggestion by Ciampolini and Speroni based on spectroscopic and magnetic data. Crystal data: C₉H₂₃Cl₂FeN₃; M = 300.06 g·mol^?1; monoclinic; space group P2₁/c (No. 14); a = 8.396(3); b = 29.556(8); c = 12.108(3) Å; β = 101.22(4)°; V = 2947(3) ų; Z = 8; d_calc = 1.352 g·cm^?3; λ_Ag?Kα = 0.56087 Å; μ = 7.02 cm^?1; F(000) = 1264; T = 293 K. Bromo- and iodo complexes of iron (II) have been prepared by using cis-FeX₂(CO)₄ (X = Br, I) as precursors. The reaction of cis-Fe(CO)₄X₂ (X = Br, I) with N,N′-dimethyl-ethylenediamine (dmeda) or N,N,N′,N′-tetramethylethylenediamine (tmeda) in heptane as medium affords adducts of general formula Fe(NN)_nX₂ ? X = Br, I; NN = dmeda, n = 2, NN = tmeda, n = 1. The iodo derivative Fe(tmeda)I₂ has been characterized by X-ray crystallography and found to be mononuclear with tetracoordinated iron (II) in a distorted tetrahedral arrangement of two iodo- and two nitrogen atoms of the bidentate amine. Crystal data: C₆H₁₆FeI₂N₂; M = 425.86 g·mol^?1; orthorhombic; space group Pbca (No. 61); a = 14.724(2); b = 15.151(4); c = 24.173.(3) Å; U = 5392(2) ų; Z = 16; d_calc = 2.098 g·cm^?3; λ_Ag?Kα = 0.56087 Å; μ = 29.52 cm^?1; F(000) = 3168; T = 293 K.