Phosphorus triiodide structure

Although 1,3,2-diazaphospholenium cations are usually prepared from neutral NHPs or 1,3,2-diazaphospholes via Lewis-acid induced substituent abstraction or A-alkylation, respectively (cf. Sect. 3.1.2), the group of Cowley was the first to describe a direct conversion of a-diimines into cationic heterocycles by means of a reaction that can be described as capture of a P(I) cation by diazabutadiene via [4+1] cycloaddition [31] (Scheme 4). The P(I) moiety is either generated by reduction of phosphorus trihalides with tin dichloride in the presence of the diimine [31] or, even more simply, by spontaneous disproportionation of phosphorus triiodide in the presence of the diimine [32], The reaction is of particular value as it provides a straightforward access to annulated heterocyclic ring systems. Thus, the tricyclic structure of 11 is readily assembled by addition of a P(I) moiety to an acenaphthene-diimine [31], and the pyrido-annulated cationic NHP 12 is generated by action of appropriate... 

A brief review has recounted the discovery and applications of phosphametallocenes. The synthesis and structure of l,l -diphospha[2]ferrocenophane have also appeared these derivatives are obtained starting with 1-phenyl-3,4-dimethylphosphole-2-carboxaldehyde in a six-step synthetic procedure. A general mini-review on phosphorus heterocycles also highlights the synthesis and use of a number of phosphaferrocenes. A phospha-ferrocenium compound has also been prepared as its triiodide [Gp Fe(Ci2H2oP)][l3]- Borane adducts of phosphaferrocenes have also been obtained simply by treating the appropriate phosphaferrocenes with boron tribromide. 

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