Boron phosphorus anions

Not many boraphosphenes are known. Salts containing anions of type [R2B = PR ]- where R,R are large groups such as mes, mes, Ph, cyclohexyl and so forth have been isolated (Figure 9.1). The B, P and nearest ring C atoms form a coplanar arrangement and the boron-phosphorus distance corresponds to that expected for a double bond. 

Phosphorus pentahalide complexes contain phosphonium cations and boron tetrahalide anions, for example, PCI4 BCI4 (Chapter 2.6). Phosphonium borohydrides, R4P BjH., can be prepared from phosphonium halides and sodium borohydride. On hydrolysis they give phosphine boranes. Salts with phosphonium cations and boron-containing anions are formed in other reactions (6.379) and (6.531). 

Handa et al. reported the synthesis of a phosphorus equivalent of Barthel s salts in which the hexavalent phosphorus(V) was coordinated by three bidentate ligands. 1.2-benzenediolato-O.C7. Its thermal stability is similar to that of its boron counterparts, and moderate ion conductivity was achieved in nonaqueous media. The authors attributed the less-than-satisfactory ion conduction to the large size of the anions, which increased the viscosity of the resultant electrolyte solutions. The anodic stability limit, as measured by voltammetry on a Ni electrode, was below 3.7 V. A preliminary test of this salt in EC/ THF was conducted in a lithium cell using the low potential cathode. V2O5. and the authors believed that this salt could be a superior electrolyte solute, judging from the utilized cell capacity that was close to the theoretical value. 

Cationic mechanisms are much more characteristic of the polymerization of oxygen heterocycles, both ethers and acetals. A wide variety of catalysts has been used, including protonic acids, such Lewis acids as boron trifluoride, phosphorus pentafluoride, stannic chloride, antimony pentachloride, titanium tetrachloride, zinc chloride, and ferric chloride, and salts of carbocations or tri-alkyloxonium ions having anions derived from Lewis acids. Some complex, coordination catalysts that appear to operate by a mechanism... 

Compared with 49, 2,5-dioxabicyclo[2.2.2]octan-3-one (54) prepared from sodium 3,4-dihydro-2//-pyran-2-carboxylate has a much low polymerization reactivity [54] Lewis acids such as antimony pentachloride, phosphorus pentafluoride, and boron trifluoride etherate were not effective at all to initiate the polymerization of 54. Trifluoromethanesulfonic acid induced the polymerization of 54, but the yield and molecular weight of the polymer were low. Bicyclic lactone 54 was allowed to polymerize with anionic and coordination initiators such as butyl-lithium, lithiumbenzophenone ketyl, and tetraisopropyl titanate. However, the... 

The chemical form and nature of the element. Most trace metal cations have a low mobility in soils because they adsorb strongly on minerals and organic matter, or form insoluble precipitates (e.g., oxides, carbonates, sulfides). Some elements that take the form of anions in soils, such as boron, are relatively mobile. Other elements that form anions, like phosphorus, are considered to be immobile because they form insoluble precipitates and bond strongly with mineral surfaces. In Figure 9.4, many of the elements of interest in soils are classified on the basis of their ionic radii and valence. The elements tend to fall naturally into one of foiu groups ... 

This has led to interesting phosphorus-boron complexes. Pentaphenyl phosphorus will donate a phenyl anion to triphenylborane ... 

Compounds with higher aggregated anions, in which the anion-forming element occurs at least twice, are termed isopoly compounds. Usually it is the alkali or ammonium salts of the isopolyacids that are S3mthesized. Compounds with isopolyanions are formed, among others, by boron, silicon, phosphorus, arsenic, sulfur, vanadium, molybdenum and tungsten. They may be prepared in a number of ways, e.g., by fusion of an acid anhydride with an alkali hydroxide, dehydration of acid salts, or treatment of a normal salt with its acid anhydride. 

---