Tantalum pentafluoride forms 1:1 and 1:2 complexes with dimethyl ether and trimethylamine. Antimony pentafluoride forms 2:1 and 1:1 complexes with dimethyl ether and trimethylamine. The rates of exchange of terminal and equatorial fluorines in the 1:1 TaF5 – dimethyl ether adduct have been measured.