Dihydrogen Tetrametaphosphate, [P[subscript 4]O][subscript 12]H[subscript 2]][superscript 2] –: Synthesis, Solubilization in Organic Media, Preparation of its Anhydride [P[subscript 4]O[subscript 11]][superscript 2] – and Acidic Methyl Ester, and Conversion to Tetrametaphosphate Metal Complexes via Protonolysis

Abstract

Dihydrogen tetrametaphosphate [P[subscript 4]O[subscript 12]H[subscript 2]] [superscript 2]- (1) can now be synthesized and isolated as its PPN salt ([PPN] + = [N(PPh[subscript 3])[subscript 2]][superscript +]) via treatment of [PPN][subscript 4 ][P[subscript 4]O[subscript 12]] with trifluoroacetic anhydride in wet acetone; this simple procedure affords the oxoacid salt in 94% yield. A pK a of 15.83 ± 0.11 in acetonitrile was determined. [P[subscript 4]O[subscript 12]H[subscript 2]][subscript 2-] reacts with the dehydrating agent N,N′-dicyclohexylcarbodiimide to afford tetrametaphosphate anhydride [P[subscript 4]O[subscript 11]][subscript 2-] (2) in 82% yield, also as the PPN salt. From 2 a monohydrogen tetrametaphosphate ester [P[subscript 4]O[subscript 10] (OH)(OMe)][superscript 2-] (3, 96%) was derived by addition of methanol, illustrating that 2 can function as a reagent for chemical phosphorylation. Addition of water to 2 regenerates 1 quantitatively. Deprotonation of 1 by metal amides in the +2 oxidation state led to the unconventional monomeric tin(II) κ[superscript 4] tetrametaphosphate [Sn(P [subscript 4]O[subscript 12])] [superscript 2-] (4, 78%, a molecular analog of SnO) and binary dimeric chromium(II) bis(μ[subscript 2] ,κ[superscript 2], κ[superscript 2]) derivative [Cr[subscript 2](P[subscript 4]O[subscript 12])[subscript 2]][superscript 4-] (5, 82%). Structural data stemming from single-crystal X-ray diffraction studies for the PPN salts of anions 1-5 are also reported.