Synthesis and Characterization of Potassium Dihydrobis-, Potassium Hydrotris- and Potassium Tetrakis (Indolyl) Borates and Their Complexes with Some Transition Metal Ions

Three new ligands, potassium dihydrobis-, potassium hydrotris- and potassium tetrakis(indolyl)borates and their complexes with Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) have been synthesized. The divalent and trivalent metal ions form complexes in 1:1 and 1:2 (metal:ligand) ratios, respectively. They were characterized by elemental analysis, magnetic susceptibility measurements, electronic and infrared spectra. On the basis of these studies Cr(III) and Fe(III) complexes with dihydrobis- and hydrotris(indolyl)borates appear to be octahedral. The divalent metal ions are supposed to have tetrahedral geometry excepting the Cu(II) for which a square planar structure is proposed. The tetrakis(indolyl)borate yielded octahedral complexes with all the above metal ions. The ligand field parameters 10Dq, B and β have also been evaluated in some cases.