Structural and mechanistic studies of co-ordination compounds. Part XII. Syntheses and characterization of some dianiono(1,4,8,11-tetra-azacyclotetradecane)-manganese(III), -iron(III), and -nickel(III) salts

Abstract

The syntheses and characterization of complexes of the type cis-[FeX₂(L⁴)]⁺[L⁴= 1,4,8,11-tetra-azacyclotetradecane (cyclam); X = Cl, Br, and NCS] and trans-[MX₂(L⁴)]⁺(M = Mn, X = Cl, Br, NCS, or N₃; M = Fe, X = Cl, Br, or NCS: and M = Ni, X = Cl or Br) are described. The assignment of geometrical configuration to these complexes is made on the basis of their i.r. spectra in the 790–910 cm^–1 region. In some cases, the assignment of a trans configuration to the dihalogeno-complexes is confirmed by the presence of only one ν(M–X) stretching frequency in their far-i.r. spectra. Magnetic susceptibilities show that all the d⁴ complexes prepared are high spin, whereas d⁶ and d⁷ complexes are low spin. For the d⁵ iron(III) system, all the cis complexes prepared are high spin, whereas trans complexes are low spin. However, trans-[FeBr₂(L⁴)][ClO₄] with µ₂₉₅ 3.90 B.M. appears to be in a high-spin–low-spin equilibrium at room temperature. The ambidentate thiocyanate ligand is N-bonded in each case. The electronic and far-i.r. spectra of these complexes are consistent with the electronic structures based on the magnetic properties.