Anionic Poly(pyrazolyl)borate Ligands Obtained from 3,5-Dimethylpyrazole and 3,5-Diphenylpyrazole and Their Cobalt(II) Complexes − X-ray Crystallographic and1H NMR Studies

Abstract

Synthesis of poly(pyrazolyl)borate anionic ligands composed of 3,5-dimethyl- and 3,5-diphenylpyrazoles and their bis(ligand) high-spin cobalt(II) complexes are described. The molecular structures of [dihydrobis(3,5-diphenylpyrazolyl)borato][hydrobis(3,5-dimethylpyrazolyl)(3,5-diphenylpyrazolyl)borato]cobalt(II) and bis[dihydro(3,5-dimethylpyrazolyl)(3,5-diphenylpyrazolyl)borato]cobalt(II) complexes were established by X-ray crystallography. The cobalt center is hexacoordinate in the former with five Co−N2(pyrazolyl) bonds and short Co−H [attached to the boron atom of bis(pyrazolyl)borate] bond (2.03 Å), whereas a distorted tetrahedral geometry was found for the latter due to four Co−N2(pyrazolyl) bonds. Additionally, the pentacoordinate homoscorpionate [tris(3,5-diphenylpyrazolyl)borato]cobalt(II) nitrate side product was obtained from the reaction and characterized structurally. It contains a κ3-coordinated Tp′ ligand and a κ2-bound nitrate anion.