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| Names | |||
|---|---|---|---|
| Preferred IUPAC name 1H-Phosphole[1] | |||
| Identifiers | |||
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3D model (JSmol) | |||
| 969375 | |||
| ChEBI | |||
| ChemSpider | |||
| |||
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| Properties | |||
| C4H5P | |||
| Molar mass | 84.058 g·mol−1 | ||
| Related compounds | |||
Related compounds | Pyrrole,bismole,arsole,stibole;phosphorine | ||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Phosphole is theorganic compound with thechemical formulaC
4H
4PH; it is thephosphorus analog ofpyrrole. The term phosphole also refers to substituted derivatives of the parentheterocycle. These compounds are of theoretical interest but also serve asligands for transition metals and as precursors to more complexorganophosphorus compounds.
Triphosphole,C
2H
3P
3, is a heterocycle with 3 phosphorus atoms.
Pentaphosphole,P
5H, is a cyclic compound with 5 phosphorus atoms.
Unlike the related 5-membered heterocyclespyrrole,thiophene, andfuran, thearomaticity of phospholes is diminished, reflecting the reluctance of phosphorus todelocalize itslone pair.[2] The main indication of this difference is thepyramidalization of phosphorus. The absence of aromaticity is also indicated by the reactivity of phospholes.[3] Phospholes undergo different cycloaddition reactions; coordination properties of phospholes are also well studied.[4]
The parent phosphole was first described in 1983. It was prepared by low-temperature protonation of lithium phospholide.[5] Pentaphenylphosphole was reported in 1953.[6] One route to phospholes is via theMcCormack reaction, involving the addition of a 1,3-diene to a phosphonous chloride (RPCl2) followed bydehydrohalogenation.[7] Phenylphospholes can be prepared via zirconacyclopentadienes by reaction withPhPCl2.[8]
The behavior of the secondary phospholes, those with P−H bond, is dominated by the reactivity of this group.[5] The parent phosphole readily rearranges by migration of H from P to carbon-2, followed by dimerization.
Most phospholes are tertiary, typically P-methyl or P-phenyl. The nonaromaticity of these phospholes is manifested in their reactivity but the P−C bonds remain intact. For example, they undergoDiels–Alder reactions withelectrophilicalkynes. They are basic at P, serving as ligands.[5]
2,5-Diphenyl phospholes can be functionalised by deprotonation followed by P-acylation then a 1H, 2H, 3H phospholide equilibrium resulting in a 1:3 shift of the acyl group.[9]
Phospholes can also be turned into β-functional phosphabenzenes (phosphinines, orphosphorine) via functionalisation byimidoyl chloride andinsertion.[10]
