Trivalent phosphorous derivatives

By single electron transfer from an electron donor, e.g. a transition metal ion, a trivalent phosphorous derivative or a base, followed by dissociation of the intermediate diazenyl radical in an aryl radical and dinitrogen. The aryl radical reacts with the solvent or with added reagents in various ways, as shown by the relatively large number of classical named reactions (Sandmeyer, Pschorr, Gomberg-Bachmann, Meerwein reactions). 

Later, the Eli Lilly group [39] reported an improved method, characterized by intercepting the sulfenate (100) with trivalent phosphorous derivatives to give (47a) directly. This process obviated the need for disulfide formation and gave in... 

Some trivalent pyramidal molecules exist in tautomeric equilibrium with tetrahedral forms. Phosphorous acid, for example, may be written as (3.37). This compound exists in tetrahedral form in the solid state or in aqueous solution, although in many of its reactions it behaves as a molecule containing trivalent P. Derivatives obtained by replacing the hydrogen by varions atoms or groups R, can usually be isolated only in one form, depending on the nature of R. Tri-esters with 3 H atoms replaced, exist only in pyramidal form (Chapter 6.8). 

Phosphate fas- fat [F, fr. acide phosphori-qwe phosphoric acid] (1795) n. (1) A salt or ester of a phosphoric acid. (2) The trivalent anion P04 derived from phosphoric acid H3PO4. (3) An organic compound of phosphoric acid in which the acid group is bound to nitrogen or a carboxyl group in a way that permits useful energy to be released. 

Exception 3. Beyond the second row, the simple Lewis model is not strictly apphed, and elements may be surrounded by more than eight valence electrons, a feature referred to as valence-shell expansion. For example, phosphorus and sulfur (as relatives of nitrogen and oxygen) are trivalent and divalent, respectively, and we can readily formulate Lewis octet structures for their derivatives. But they also form stable compounds of higher valency, among them the familiar phosphoric and sulfuric acids. Some examples of octet and expanded-octet molecules containing these elements are shown below. 

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