Syntheses and structures of lanthanide(III) complexes with some bis(pyrazolyl)borate and tris(pyrazolyl)borate podand ligands

Abstract

Two new poly(pyrazolyl)borate ligands have been prepared: potassium tris[3-{(4- t butyl)-pyrid-2-yl}-pyrazol-1-yl]hydroborate (KTp BuPy) which has three bidentate arms and is therefore hexadentate; and potassium bis[3-(2-pyridyl)-5-(methoxymethyl)pyrazol-1-yl]-dihydroborate (KBp (COC)Py) which has two bidentate arms and is therefore tetradentate. The crystal structures of their lanthanide complexes [La(Tp BuPy)(NO 3) 2] and [La(Bp (COC)Py) 2X] (X=nitrate or triflate) have been determined. In [La(Tp BuPy)(NO 3) 2] the metal ion is ten-coordinate, from the hexadentate N-donor podand ligand and two bidentate nitrates. [La(Bp (COC)Py) 2(NO 3)] is also ten-coordinate, from two tetradentate ligands and a bidentate nitrate, but in [La(Bp (COC)Py) 2(CF 3SO 3)] the metal ion is nine-coordinate because the triflate anion is monodentate. Two unexpected new complexes which arose from partial decomposition of the poly(pyrazolyl)borate ligands have also been characterised structurally. In [La( BuPypzH) 3(O 3SCF 3) 3] the metal ion is nine-coordinate from three bidentate pyrazolyl-pyridine arms (liberated by decomposition of KTp BuPy) and three triflate anions; there is extensive NH· · · O hydrogen-bonding between the pyrazolyl and triflate ligands. [Nd(Tp Py)(Bp Py)][Nd(PypzH)(NO 3) 4] was isolated from the reaction of hexadentate tris[3-(2-pyridyl)-pyrazol-1-yl]hydroborate (Tp Py) with Nd(NO 3) 3. One of the Tp Py ligands has lost one bidentate pyrazolyl-pyridine ‘arm’ (PypzH) to leave tetradentate tris[3-(2-pyridyl)-pyrazol-1-yl]dihydroborate (Bp Py). In this structure, the cation [Nd(Tp Py)(Bp Py)] + is ten-coordinate from inter-leaved hexadentate and tetradentate ligands, and the anion [Nd(PypzH)(NO 3) 4] − is also ten-coordinate from the bidentate N-donor ligand PypzH and four bidentate nitrates.