The reactivity of halides of high valent groups 5 and 6 metals with oxygen and nitrogen organic donors and the parallelism with related chemistry of main groups

Homoleptic halides of high-valent transition metals are acidic species possessing a strong affinity to N- and O-donors. The formation of coordination adducts with related organic ligands may be a prelude to subsequent activation reactions proceeding according to a variety of unconventional reactivity patterns. General aspects regarding the structure, the preparation, the properties and the salient reactivity of halides of elements belonging to groups 5, 6, 15 and (to a lesser extent) 16 of the periodic table, in an oxidation state of +V or + VI (when available), will be provided. Then, focusing on the most easily available metal halides (MX5, M = Nb or Ta, X = F or Cl; MoCl5 and WCl6), the direct reactions with different categories of oxygen (carbonyl compounds, ethers, alcohols) and nitrogen (amines, imines, nitriles) organics will be discussed using a comparative approach, including the parallel chemistry of the pentahalides of group 15.