Synthesis of Ca(PF$_6$)$_2$, formed $\textit{via}$ nitrosonium oxidation of calcium

The development of rechargeable Ca-ion batteries as an alternative to Li systems has been limited by the availability of suitable electrolyte salts. We present the synthesis of complexes of Ca(PF$_6$)$_2$ (a key potential Ca battery electrolyte salt) $\textit{via}$ the treatment of Ca metal with NOPF$_6$, and explore their conversion to species containing PO$_2$F$_2$$^{-}$ under the reaction conditions.