title: Interaction of niobium and tantalum pentahalides with O-donors: coordination chemistry and activation reactions.
abstract: The chemistry of niobium and tantalum pentahalides, MX(5), with oxygen compounds is reviewed herein. The polynuclear structure of MX(5) is readily broken by addition of oxygen-containing organic molecules, L, to give either mononuclear or ionic dinuclear coordination adducts. Then activation of the organic ligand may take place favoured by several factors, i.e. low M-X bond energy, high temperature, presence of more than one oxygen function within L, L/M molar ratio ≥ 2. The activation reactions are often uncommon in the context of metal halides; they include the cleavage of C(sp3)-O, C(sp2)-O, C-H and C-C bonds, and eventual successive rearrangements proceeding with C-O or C-C couplings. The recently elucidated reactivity of MX(5) with limited amounts of oxygen compounds will be presented, and possible connections with the relevant MX(5)-directed syntheses reported in the literature will be outlined.
authors.affiliation: Università di Pisa, Dipartimento di Chimica e Chimica Industriale, Via Risorgimento 35, I-56126 Pisa, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Marchetti
authors.forename: Guido
authors.initials: G
authors.lastname: Pampaloni