Cyclopentaphosphine

Cyclopentaphosphine is the inorganic compound with the formula (PH)₅. It is prepared by the hydrolysis of cyclo-(PSiMe₃)₄. Although only of theoretical interest, (PH)₅ is parent of many related cyclic polyphosphines that are the subject of research.

Cyclopentaphosphine

Names
IUPAC name pentaphospholane
Other names Cyclopentaphosphane, pentaphosphole
Identifiers
CAS Number	6798-45-4 Y
3D model (JSmol)	Interactive image
ChemSpider	546991
EC Number	235-633-3
PubChem CID	629880
CompTox Dashboard (EPA)	DTXSID50924646
InChI InChI=1S/H5P5/c1-2-4-5-3-1/h1-5H Key: MSVKYECZFNAJJY-UHFFFAOYSA-N
SMILES P1PPPP1
Properties
Chemical formula	P5H5
Molar mass	159.909 g/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Organic cyclophosphines

Structure of (2-pyridylP)₅.^[1] Color code: maroon = P, black = C, white = H, blue = N.

Organic cyclophosphanes are a family of organophosphorus compounds with the formula (RP)_n where R is an organic substituent. Many examples are known. They are white, air-sensitive solids which have good solubility in organic solvents. Well-characterized examples are known for ring sizes 3–6. The three-membered rings feature bulky substituents, e.g., [tert-BuP]₃.

The cyclophosphines can be prepared by several methods, one involves reductive coupling of dichlorophosphines:^[2]

5PhPCl₂ + 5 Mg → (PhP)₅ + 5 MgCl₂

Isomerism

The structures are complicated by the slow pyramidal inversion at phosphorus(III). In principle, many isomers are possible for cyclo-P₅R₅, but usually only one is observed.^[3] All phenyl substituents are equatorial in cyclo-P₆(C₆H₅)₆.^[4]