Dihydrogen tetrametaphosphate, [P4O12H2]2-: synthesis, solubilization in organic media, preparation of its anhydride [P4O11]2- and acidic methyl ester, and conversion to tetrametaphosphate metal complexes via protonolysis.

Dihydrogen tetrametaphosphate [P4O12H2](2-) (1) can now be synthesized and isolated as its PPN salt ([PPN](+) = [N(PPh3)2](+)) via treatment of [PPN]4[P4O12] with trifluoroacetic anhydride in wet acetone; this simple procedure affords the oxoacid salt in 94% yield. A pKa of 15.83 ± 0.