Phosphorus oxoanions

The oxoacids and oxoanions of phosphorus are among the most heavily manufactured chemicals. Phosphate fertilizer production consumes two-thirds of all the sulfuric acid produced in the United States. 

Phosphorus forms a wide variety of oxoanions, which outnumber those formed by any other element except silicon [ 1 ]. Many of these anionic hgands are of industrial importance and their derivatives are essential components of numerous biological processes. Some of the more common examples include orthophosphate PO " (1), phosphite HPO " (2) and metaphosphate PO3 (3). 

Equilibrium constants for formation of iron(III) complexes of several oxoanions, of phosphorus, arsenic, sulfur, and selenium, have been reported. The kinetics and mechanism of complex formation in the iron(III)-phosphate system in the presence of a large excess of iron(III) involve the formation of a tetranuclear complex, proposed to be [Fc4(P04)(0H)2(H20)i6]. The high stability of iron(III)-phosphate complexes has prompted suggestions that iron-containing mixed hydroxide or hydroxy-carbonate formulations be tested for treatment of hyperphosphatemia. " ... 

Analogous oxoanions of elements in the same group of the periodic table are named similarly. Based on the names of the oxoanions of phosphorus and sulfur, name the following anions ... 

In spite of much information available for the interactions of various metal ions with small oxoanions of phosphorus, relatively little information has been obtained for the complex formation of long-chain polyphosphate ion. This may be due to the fact that the conventional methods useful for the study of the complex formation of a relatively small ligand are not always applicable to the polyanion complex formation system. Since a gel chromatographic method based on the same principle as the equilibrium dialysis method has been proved to be applicable in the field of inorganic complex chemistry (1), this method has been applied to the study of the binding of long-chain polyphosphate ions to magnesium ion. 

Phosphorus has an even wider range of oxoacid chemistry, and a commensurately wide range of phosphates, phosphites, polyphosphates, hypophosphites, and so on of the alkali metals are preparable. Sodium and potassium are the most common cations used, largely because of their availability and low cost. The cation often has little effect on the properties and applications, which are covered in Phosphates Solid-state Chemistry. Most form a variety of crystalline hydrates, which have been well covered in previous treatments and need not be repeated here. Trae to form, lithium is the exception, forming no stable hydrates with phosphorus oxoanions. 

E9.14 The atomic number of P is 15. The Z + 8 element has an atomic number of 23 and is V (vanadium). Both form compounds with varying oxidation states up to a maximum value of +5. Both form stable oxides including ones in +5 oxidation state (V2O5 and P1O5). Like phosphorus, vanadium forms oxoanions including ortho-, pyro-, and meta-anions. Consult Section 15.5 for analogous phosphorus oxoanions. 

Oxoanions of phosphorus are buffer components in blood. For a KH2P04-Na2HP04 solution with pH = 7.40 (pH of normal arterial blood), what is the buffer-component concentration ratio ... 

Reactions of three-co-ordinate phosphorus(v) include hydrogen exchange in hypophosphites and condensation of phosphite with chromate. This latter is not a redox reaction, in contrast to such apparently similar systems as chromate plus thiosulphate, which is an 5/j-oxoanion analogue of the classical inner-sphere redox mechanism of transition-metal complex chemistry. Several associative mechanisms are feasible for reactions of phosphites with thionyl chloride. The phosphorus lone-pair can approach either the sulphur, the oxygen, or perhaps even one of the chlorines, which are rendered slightly positive by electron withdrawal to other sites in the thionyl chloride molecule. ... 

Phosphorus.—Reactions of oxoanions and related species, phosphorus-oxygen-nitrogen compounds, phosphazanes, and other components and intramolecular processes are considered in this section. 

A review has appeared on the kinetics of hydrolysis of phosphate esters. Hydroxyphosphoranes have long been postulated as intermediates in the hydrolysis of esters of oxoacids of phosphorus. Compound (4), which is a possible model for such species, has been synthesized. Nucleophilic substitution at cis-and /raiij-isomers of (5) (X=/ N02CeH4) by nucleophilic oxoanions in aprotic solvents gives complex results. The degree of retention/inversion is strongly dependent upon the cation, and on the solvent. The inversion process involves an Ssl tbp-type transition state, while the retention process is suggested to involve the addition of an ion pair across the P=0 bond to form a square-pyramidal species. ... 

Phosphorus forms more oxoacids than any other element, and the number of oxoanions and 0x0 salts ranks second only to silicon. Phosphoric acid, H3PO4, ranks seventh among the top 50 chemicals in production, and sodium tripolyphosphate, NasPsOio, ranks just outside the top 50. NasPsOio may be regarded as a salt of triphosphoric acid, H5P3O10, whose structure is as follows ... 

Phosphorus.—Oxoanions. Evidence for the formation of the metaphosphate anion [POs] as an intermediate in acyl phosphate reactions has been reported, and ah initio calculations on this species suggest that its high electrophilicity may be due to contributions from both n and o molecular orbitals. Its methyl ester, MeOPOa, can substitute electrophilically in the aromatic ring for activated aro-... 

Phosphorus Oxoacids and Oxoanions The two common phosphorus oxoacids are phosphorous acid (note the change in spelling) and phosphoric acid. 

The chemistry of phosphorus and the heavier congeners is dominated by element to element (E-E) single bonds and, particularly in the case of phosphorus, the availability of l>d orbitals to form dir—pir double bonds with a variety of other atoms such as oxygen, nitrogen, and even sulfur. Orbital participation results in expanded octets as found in compounds such as PF5, SbCl5, X3P=0 (where X=F, Cl, Br, I), the phosphorus oxoadds and oxoanions, and a class of compounds called the phosphazenes. We will take up many of these cases as we encounter them in the appropriate sections under our usual survey of the hydrides, oxides and oxoacids, and halides. For now, however, let s take a quick look at the phosphazenes, formerly called the phosphonitriles, that contain both N and P atoms in the same molecule. 

Phosphorus.—Oxoanions and Related Species. Ab initio and semi-empirical molecular orbital calculations on the metaphosphate anion [PO3]- attribute the electrophilic reactivity of this species to a low-lying acceptor orbital of a symmetry, nearly degenerate with a n molecular orbital. This species, metaphosphate, is suggested as intermediate in one of the two pathways involved in phosphorylation by phosphorocreatine. Kinetic isotope effect studies indicate that metaphosphate is also generated in the hydrolysis of 2,4-dinitrophenylphosphate ... 

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