Alkaloids as ligands. 2. Synthesis and characterization of iron(II) halide complexes containing l-sparteine

Abstract

Iron(II) compounds of l-sparteine, sp, are four-coordinate, pseudotetrahedral complexes of the type Fe(sp)X 2, where X is Cl, Br, or I. The infrared spectra suggest that sp adopts an all-chair conformation in these complexes. Furthermore, the infrared spectra show four bands below 600 cm −1, two of which are halide sensitive. These absorptions have been assigned to iron-ligand stretching modes. X-ray powder patterns of Fe(sp)Cl 2 and Fe(sp)Br 2 are identical to the analogous pseudotetrahedral cobalt(II) compounds. These iron compounds have room temperature magnetic moments close to 5.3 μ B and display a characteristics low-intensity absorption near 4000 cm −1 which has been assigned to the 5E → 5T 2 ligand-field transition. Mössbauer effect spectral results indicate the quadrupole interaction is approximately 2.9 mm/s. The chemical isomer shift increases from 1.03 to0 1.25 to 1.29 mm/s (relative to α-iron foil) for the chloride, bromide, and iodide complexes respectively. The latter two values are among the highest observed for tetrahedral iron(II) complexes.