Phosphates 75 anions

Phosphoric acids and the phosphates maybe defined as derivatives of phosphoms oxides where the phosphoms atom is in the +5 oxidation state. These are compounds formed in the M2O—P20 system, where M represents one cation equivalent, eg, H", Na", 0.5 Ca ", etc. The molecular formula of the phosphoms(V) oxide [1314-56-3] is actually P O q, but this oxide is commonly referred to in terms of its empirical formula, P2O5. StmcturaHy, four phosphoms—oxygen (P—O) linkages are arranged in an approximate tetrahedral configuration about the phosphoms atom in the phosphate anion. Compounds containing discrete, monomeric PO ions are known as orthophosphates or simply as phosphates. 

Competition of Phosphate Anions and Metal Cations for Macrocyclic... 

Phosphorus (eleventh most abundant element) occurs mostly as the phosphate anion, P04-3, in such minerals as phosphate rock, which is a... 

When the three ligands are the same, procedures similar to the ones developed by Hellwinkel [16,17], Koenig [25-28] and coworkers can be utilized -that is the one-time addition of three equivalents of bidentate ligands to PCI5 to afford the hexacoordinated phosphate anions. Ligands as varied as malonic acid,3,3,3-trifluoro-2-hydroxy-2-trifluoromethyl-propionic acid or oxalic acid have been used to form 5,6, and 7,respectively [29]. Aromatic 1,2-diols are also particularly good ligands as tetrachloropyrocatechol [30, 31], 4-methylpyro-... 

Following a similar protocol, novel hexacoordinated phosphate anions 19 to 22 bearing two different dioxo ligands could be simply prepared as their di-methylammonium salts from the reaction of tetrachlorocatechol derived phos-phoramidite 23 with a variety of symmetrical diones other than o-chloranil (a-diketones or orf/zo-quinones) and subsequent addition of tetrachlorocatechol to the corresponding phosphorane 24 (Scheme 3) [42]. 

Finally, two more anionic phosphate anions with six oxygen substituents at phosphorus (Fig. 5) were isolated by serendipity. Compound 25 [43] was isolated from the reaction of naphthalene-2,3-diol and phosphonitrilic chloride in... 

The stereoselective synthesis of hexacoordinated phosphate anions was also reported by the same group. A general one-pot process was developed for the preparation of C2-symmetric anions 15,16 and 17 containing enantiopure BINOL, hydrobenzoin, and tartrate-derived ligands respectively [38-40] Cpsymmetric anion 18 being prepared similarly in two steps from methyl-a-... 

Fig. 20 Diastereomeric purity and relative configuration of enantiopure chiral phosphate anions 15 to 18 isolated after initial precipitation...

The strong Bronstedt acid nature of some hexacoordinated phosphorus derivatives, [7",H ] (Et20)4 in particular, was recently used within the context of an industrial application [36]. The conjugated acid of tris(oxalato)phosphate anion 7 was found to effectively catalyze the ring-forming reaction of trimethyl-hydroquinone 63 with isophytol 64 to give (all rac)-a-tocopherol 65 (ethylene-carbonate/heptane 1 1,100 °C, 90%, Scheme 19). This process is particularly... 

Unfortunately, in most of the previous examples, the extent of the asymmetry-induction was determined by chiroptical measurements (ORD, CD) that gave qualitative and not quantitative information. The NMR chiral shift efficiency of TRISPHAT 8 and other hexacoordinated phosphate anions was therefore considered as an excellent analytical tool to provide accurate measurement of the induced selectivity by NMR spectroscopy. 

An excess of potassium hydroxide means that there are enough OH" ions to remove all three acidic hydrogens from phosphoric acid. This reaction produces three molecules of water and one phosphate anion H3 PO4 aq) + 3 OH a q) PO (t2 < ) + 3 H2 O (/)... 

C17-0018. Identify the conjugate acid and the conjugate base of the dihydrogen phosphate anion, H2 PO4, and the hydrogen phosphate anion, HP04. ... 

Use chemical behavior and electronegativities to assess the reasonableness of the assignments. Phosphoric acid can be viewed as the phosphate anion (-3 charge) associated with three H ions. Sodium, an alkali metal, readily forms cations with +1 charge, hi KH, the assignments are consistent with the electronegativities (jjf) of the two elements — 0.8, = 2.1. 

C21-0015. Figure 21-11 highlights the triangular arrangement of phosphorus atoms in P4 Oio. As every P atom bonds to four O atoms, however, the geometry about each P atom is tetrahedral, just as in the phosphate anion. Redraw Figure 21-11 in a way that highlights one of the tetrahedral PO4 units. 

C21-0053. Three phosphate anions can condense to form a ring whose chemical formula Is P3 Og. Determine the Lewis structure and draw a ball-and-stick model of this anion. 

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