Heavier halides of transition metals by halide exchange

The classical preparations of heavier (bromides or iodides) metal halides of the d or f transition series from the elements can be almost systematically substituted by one of the exchange reactions summarized in this article, by using HX or RX (X = Br, I) as reagent. These enthalpy-driven reactions are normally largely favoured thermodynamically and can be best carried out at room temperature or even lower.