Inter- and Intramolecular Hydrogen-Bonding Interaction of Hydroxo Groups and Steric Effect of Alkyl Substituents on Pyrazolyl Rings in TpR Ligands: Synthesis and Structural Characterization of Chloro-, Acetylacetonato-, and Hydroxo Complexes of VO2+ with TpPri2 and TpMe2 Ligands

Abstract

Novel vanadyl (VO2+) chloro and hydroxo complexes with the hindered TpPri2 (hydrotris(3,5-diisopropyl-1-pyrazolyl)borate) and TpMe2 (hydrotris(3,5-dimethylpyrazolyl-1-pyrazolyl)borate) ligands were prepared and structurally characterized successfully. Ligand displacement of VOCl2(MeCN)2(H2O) by TpR afforded a series of octahedral chloro complexes, TpRV(O)(Cl)(X) (1: R = Pri2, X = PzPri2H; 2: R = Pri2, X = py; 6: R = Me2, X = NCMe). Hydrolysis of the obtained chloro complexes yielded the corresponding hydroxo complexes 4, 5, and 7, but their structures were very unique and different from that of the previously reported dinuclear VO2+ bis(μ-hydroxo) complex with the less hindered TpH2 (hydrotris(1-pyrazolyl)borate) ligand. For the TpPri2 complexes, the octahedral hydroxo−aqua complex, TpPri2V(O)(OH)(OH2) (4), and the trinuclear bis(μ-hydroxo)bis(μ-pyrazolato) complex, TpPri2V(O)(μ-OH)(μ-PzPri2)V(O)(μ-OH)(μ-PzPri2)V(O)TpPri2 (5), were isolated. The hydroxo−aqua complex 4 was dimerized through the intermol...