Nitric oxide reacts with hydrated ReO2 in aqueous suspension at 70–80°C to produce quantitatively Re(NO)(OH)3, ReO 4− and NH 4+. [Re(NO)Cl5]2− and ReO 4− are produced in stoichiometric quantities by the reaction of either NO with ReO2 suspension in 6 N HCl or by the action of a mixture of NO and HCl with an aqueous ethanolic or aqueous suspension of ReO2 at 70–80°C. Passage of NO over 1,10‐phenanthrolinium hexahalorhenate(IV) at 220°C produces nitrosyl halide, hydrogen halide and [Re(NO) (phen)Cl3] or [Re(NO)(phen)Br3]. Copyright © 1973 Verlag GmbH & Co. KGaA, Weinheim