Diphosphorus

Diphosphorus
IUPAC name Diphosphorus
Systematic name Diphosphyne[1]
Identifiers
CAS number	12185-09-0 Y
PubChem	5460700
ChemSpider	4574176 Y
ChEBI	CHEBI:33472 Y
Gmelin Reference	1400241
Jmol-3D images	Image 1
SMILES P#P
InChI InChI=1S/P2/c1-2 Y Key: FOBPTJZYDGNHLR-UHFFFAOYSA-N Y InChI=1/P2/c1-2 Key: FOBPTJZYDGNHLR-UHFFFAOYAU
Properties
Molecular formula	P2
Molar mass	61.95 g mol−1
Exact mass	61.947523024 g mol-1
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Diphosphorus, P₂, is the diatomic form of phosphorus.^[2] Unlike its nitrogen group neighbor nitrogen, which forms a stable N₂ molecule with a nitrogen to nitrogen triple bond, phosphorus prefers a tetrahedral form P₄ because P-P pi-bonds are high in energy. Diphosphorus is, therefore, very reactive with a bond-dissociation energy (117 kcal/mol or 490 kJ/mol) half that of dinitrogen.

Diphosphorus has been generated by heating white phosphorus at 1100 kelvins. Nevertheless, some advancements have been obtained in generating the diatomic molecule in homogeneous solution, under normal conditions with the use by some transition metal complexes (based on, for example, tungsten and niobium).^[3][4]

The molecule attracted attention in 2006, when a new method for its synthesis at milder temperatures emerged.^[5]

This method is a variation on nitrogen expulsion in azides with formation of a nitrene. The synthesis of the diphosphorus precursor consists of reacting a terminal niobium phosphide with a chloroiminophosphane:

Heating this compound at 50 °C in 1,3-cyclohexadiene serving as a solvent and as a trapping reagent expulses diphosphorus, which is reactive, as it is forms a double Diels-Alder adduct and the niobium imido compound:

The same imido compound also forms when the thermolysis is performed in toluene but then the fate of diphosphorus is unknown.

P₂ has been suggested to form as an intermediate in the photolysis of P₄ ^[6] and in the presence of 2,3-dimethylbutadiene the diphosphane is again formed ^[7] To date, no direct evidence of P₂ formation via P₄ photolysis exists.

References

1. ^ "Diphosphorus (CHEBI:33472)". Chemical Entities of Biological Interest (ChEBI). UK: European Bioinformatics Institute. https://www.ebi.ac.uk/chebi/searchId.do?chebiId=33472. 
2. ^ Russell, C. A. (2010), PP, a Laboratory Reagent?. Angewandte Chemie International Edition, 49: 9572–9573. doi:10.1002/anie.201006243
3. ^ Triple-Bond Reactivity of Diphosphorus Molecules Nicholas A. Piro, Joshua S. Figueroa, Jessica T. McKellar, Christopher C. Cummins Science 1 September 2006:Vol. 313. no. 5791, pp. 1276–1279 10.1126/science.1129630
4. ^ http://www.sciencemag.org/cgi/reprint/313/5791/1276.pdf
5. ^ Triple-Bond Reactivity of Diphosphorus Molecules Nicholas A. Piro, Joshua S. Figueroa, Jessica T. McKellar, Christopher C. Cummins Science 1 September 2006:Vol. 313. no. 5791, pp. 1276 - 1279 doi:10.1126/science.1129630 PMID 16946068
6. ^ Optische und photochemische versuche mit phosphor G. Rathenau Physica Volume 4, Issue 6, June 1937, Pages 503-514 doi:10.1016/S0031-8914(37)80084-1
7. ^ Tofan, D. and Cummins, C. C. (2010), Photochemical Incorporation of Diphosphorus Units into Organic Molecules. Angewandte Chemie International Edition, 49: 7516–7518. doi: 10.1002/anie.201004385

External links

• Ron Dagani, "A Mild Route To P2, Chemical & Engineering News September 4, 2006 Link