Ligand-interchange reactions between M(iv) (M = Ti, V) oxide bis-acetylacetonates and halides of high-valent group 4 and 5 metals. A synthetic and electrochemical study

Abstract

The reactions of M′O(acac)₂ [M′ = Ti, V; acac = acetylacetonato anion] with equimolar amounts of MF₅ (M = Nb, Ta) in CH₂Cl₂ afforded Ti(acac)₂F₂, 1a, and [V(acac)₃][MF₆] (M = Nb, 4a; M = Ta, 4b), respectively. MOF₃ (M = Nb, 2a; M = Ta, 2b) were co-produced from MF₅/TiO(acac)₂. The intermediate species [TaF₄{OTi(acac)₂}₂][TaF₆], 3, was intercepted in the course of the formation of 1a from TiO(acac)₂/TaF₅. NbCl₅ reacted with TiO(acac)₂ yielding selectively the previously reported [NbO(acac)Cl₂]_x, 5, and Ti₂(acac)₂(μ-Cl)₂Cl₄, 6. Complex 6 was alternatively obtained from the addition of a two-fold excess of TiCl₄ to VO(acac)₂. The 1 : 1 reactions of TiX₄ (X = F, Cl) with TiO(acac)₂ in dichloromethane gave Ti(acac)₂X₂ (X = F, 1a; X = Cl, 1b) and TiOX₂ (X = F, 7a; X = Cl, 7b). The 1 : 1 combination of TiX₄ (X = F, Cl) with VO(acac)₂ led to 1a,b and VOX₂ (X = F, 8a; X = Cl, 8b). The μ-oxido compounds (C₆F₅)₃B–O–M′(acac)₂ (M′ = Ti, V) underwent fragmentation by [PF₆]⁻ in chlorinated solvent, yielding POF₃, 9, and [B(C₆F₅)₃F]⁻, 10, according to NMR studies; 1a and V(acac)₃⁺, respectively, were detected as the metal-containing species. Electrochemical studies were carried out aiming at the full characterization of the products and the observation of possible degradation pathways.