Phosphorus and silicon

The chemistry of compounds containing phosphorus and Group IV elements other than carbon, has been much less explored than that of phosphorus with the latter element. In a distinction parallel to that made between organophosphorus and organic phosphorus compounds in Chapter 6.1, it is convenient to divide the compounds with Group IV elements into (a) those which contain a P-X bond (where X = Si, Ge, Sn or Pb), and (b) those which do not. In recent years, a special interest in compounds with P-Si linkages has developed [8]. 

The P-X bond is generally less stable than the P-C bond, and compounds containing P-X bonds are almost aU unstable to air and water. Their thermal stabilities generally decrease with increasing atomic weight of X. The corresponding compounds with As-X bonds are in most cases known. 

In the same way that esters form the most important group of organic phosphorus compounds, compounds containing P-O-X linkages are at present the most prominent among those in group (b) above. In spite of the formal periodic relationship of silicon to carbon, and the relative abundance of silicon in the earth s crust, there is as yet little evidence that compounds with P-O-Si (or P-Si) linkages are involved on any major scale in life processes.  

Compounds containing both silicon and phosphorus are cited in the patent literature as useful anti-foaming agents, polymeric materials, plasticisers, oil additives and flameproofing agents. 

In common with carbon, silicon has the capacity to form multiple bonds to P. By analogy with carbon, silicon might be capable of forming analogues of all the possible bond arrangements depicted in Table 6.1. At the present time, however, a simple division of known phosphorus-silicon compounds into three major groups will suffice (9.165). Almost all of these are silaphosphines. 

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J. D. Morrison and J. W. ScoXt, Asymmetric Synthesis, Vol. 4, The Chiral Carbon Pool and Chiral Sulfur, Nitrogen, Phosphorus, and Silicon Centers, Academic Press, Inc., Odando, Fla., 1984. 

For medium- to high-impact applications a wide range of low-alloy steels are produced containing some chromium, molybdenum, phosphorus, and silicon. Economy of manufacture is a benefit for selec tion of these steels. 

Table 3.1 gives the local elemental composition of three different tubercles from three different systems formed under different chemical treatments. At the floor of each tubercle, the concentration of chlorine and sulfur is higher than in the crust. The concentration of most crust elements, except that of iron, also decreases near the tubercle floor. The crust contains traces of treatment chemicals including zinc, phosphorus, and silicon. Tubercle 1 contains up to 40% silicon in the crust, which strongly suggests accumulation of silt by settling of particulate. 

Phosphorus and Silicon in Waters, Effluents and Sludges [e.g. Phosphorus in Waters, Effluents and Sludges by Spectrophotometry-phosphomolybdenum blue method. Phosphorus in Waters and Acidic Digests by Spectrophotometry-phosphovanadomolybdate method. Ion Chromatographic Methods for the Determination of Phosphorus Compound, Pretreatment Methods for Phosphorus Determinations, Determination of silicon by Spectrophotometric Determination of Molybdate Reactive Silicon-1 -amino-2-naphthol-4, sulphonic acid (ANSA) or Metol reduction methods or ascorbic acid reduction method. Pretreatment Methods to Convert Other Eorms of Silicon to Soluble Molybdate Reactive Silicon, Determination of Phosphorus and Silicon Emission Spectrophotometry], 1992... 

Driess, Matthias, Silicon-Phosphorus and Silicon-Arsenic Multiple Bonds. 39 193... 

In sharp contrast to molecular solids, network solids have very high melting points. Compare the behavior of phosphorus and silicon, third-row neighbors in the periodic table. As listed in Table 11-2. phosphorus melts at 317 K, but silicon melts at 1683 K. Phosphorus is a molecular solid that contains individual P4 molecules, but silicon is a network solid in which covalent bonds among Si atoms connect all the atoms. The vast array of covalent bonds In a network solid makes the entire stmcture behave as one giant molecule. ... 

The iron formed in a blast furnace, called pig iron, contains impurities that make the metal brittle. These include phosphorus and silicon from silicate and phosphate minerals that contaminated the original ore, as well as carbon and sulfur from the coke. This iron is refined in a converter furnace. Here, a stream of O2 gas blows through molten impure iron. Oxygen reacts with the nonmetal impurities, converting them to oxides. As in the blast furnace, CaO is added to convert Si02 into liquid calcium silicate, in which the other oxides dissolve. The molten iron is analyzed at intervals until its impurities have been reduced to satisfactory levels. Then the liquid metal, now in the form called steel, is poured from the converter and allowed to solidify. 

Synopsis of dangerous reactions of sulphur, phosphorus and silicon derivatives... 

Figure 5.10. EPMA maps for nickel, arsenic, phosphorus and silicon in a 1st century AD Roman mattock blade. Scale bar = 1 mm. (Courtesy Dr C.J. Salter, Oxford University.)...

Silicon-Phosphorus and Silicon-Arsenic Multiple Bonds... 

The impurities in pig iron, the iron formed in a blast furnace, that make it brittle include four elements phosphorus and silicon, two elements that came from the silicate and phosphate minerals that contaminated the original ore, and carbon and sulfur that came from the coke. 

Synthesis of Fused Ring Systems with Phosphorus and Silicon Ring Atoms 842... 

Atomic absorption spectrometric methods and, more recently, the inductively coupled plasma atomic emission method, are, of course, mandatory if determination of elements is required (arsenic, selenium, boron, phosphorus and silicon). 

A British standard method [93] has been published for the determination of phosphorus and silicon in sludges. 

Standing Committee of Analysts (1992) Phosphorus and Silicon in Effluents and Sludges 1992. 2nd edn. Methods for the Examination of Water and Associated Materials, HMSO, London. 

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