Abstract: The invention provides process for preparing tin or germanium monochalcogenides of cubic crystalline structure, the process comprises combining a source of tin or germanium and a source of chalcogenide in a reaction vessel in the presence of uncharged liquid primary amine R—NH2 and a charged form R—NH3+ associated with a counter anion, wherein R is saturated or unsaturated hydrocarbyl, which may be the same or different in the uncharged and charged forms, and recovering from the reaction mixture an essentially pure cubic phase of the monochalcogenides.