An electrochemical cell consisting of cobalt ([Co-II/III(P3O9)(2)](4-/3-)) and vanadium ([V-III/II-(P3O9)(2)](3-/4-)) bistrimetaphosphate complexes as catholyte and anolyte species, respectively, was constructed with a cell voltage of 2.4 V and Coulombic efficiencies >90% for up to 100 total cycles. The [Co(P3O9)(2)](4-) (1) and [V(P3O9)(2)](3-) (2) complexes have favorable properties for flow-battery applications, including reversible redox chemistry, high stability toward electrochemical cycling, and high solubility in MeCN (1.09 +/- 0.02 M, [PPN](4) [1]center dot 2MeCN; 0.77 +/- 0.06 M, [PPN](3) [2]center dot DME). The [PPN](4)-[1]center dot 2MeCN and [PPN](3) [2]center dot DME salts were isolated as crystalline solids in 82 and 68% yields, respectively, and characterized by 31 P NMR, UV/vis, ESI-MS(-), and IR spectroscopy. The [PPN](4)[1]center dot 2MeCN salt was also structurally characterized, crystallizing in the monoclinic P2(1)/c space group. Treatment of 1 with [(p-BrC6H4)(3)N](+) allowed for isolation of the one-electron-oxidized spincrossover (SCO) complex, [Co(P3O9)(2)](3-) (3), which is the active catholyte species generated during cell charging. The success of the 1-2 cell provides a promising entry point to a potential future class of transition-metal metaphosphate-based all-inorganic non-aqueous redoxflow battery electrolytes.