The Synthesis and Ligand Properties of the Dihydrobis-, Hydrotris- and Tetrakis (6-Nitroindazolyl) Borate Anions

The potassium salts of the three new potential chelating ligands dihydrobis-, hydrotris- and tetrakis(6-nitro-indazoly1)borate anions have been synthesized by refluxing potassium borohydride and 6-nitroindazole in DMF in the appropriate molar ratio. These salts have been used to form complexes with the 3d transition metal ions vanadium through copper. The complexes of dihydrobis(6-nitroindazoly1)borate anion with V(III) and Fe(III) are octahedral, whereas Mn(II), Co(II), Ni(II) and Cu(II) complexes have tetrahedral geometry. The Cr(II) complex has been observed to be tetragonally distorted. The hydrotris(6-nitroindazoly1)borate anion gave rise to only octahedral complexes of the above metal ions except for Cr(II) and Cu(II) which gave rise to complexes with tetragonally distorted octahedral geometry. The tetrakis(6-nitroindazoly1)-borate anion is found to be a substituted variant of the hydrotris ligend.