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

Two new poly(pyrazolyl)borate ligands have been prepared: potassium tris[3-{(4-'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))(NO3)(2)] and [La(Bp((COC)Py))(2)X] (X = nitrate or triflate) have been determined. In [La(Tp(BuPy))(NO3)(2)] the metal ion is ten-coordinate, from the hexadentate N-donor podand ligand and two bidentate nitrates. [La(Bp((COC)Py))(2)(NO3)] is also ten-coordinate, from two tetradentate ligands and a bidentate nitrate, but in [La(Bp((COC)Py))(2)(CF3SO3)] 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((Bu)PypzH)(3)(O3SCF3)(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)(NO3)(4)] was isolated from the reaction of hexadentate tris[3-(2-pyridyl)-pyrazol-1-hydroborate (Tp(Py)) with Nd(NO3)(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)(NO3)(4)](-) is also ten-coordinate from the bidentate N-donor ligand PypzH and four bidentate nitrates. (C) 2001 Elsevier Science Ltd. All rights reserved.