Organophosphorus



Organophosphorus compounds are nitrogen and phosphorus compounds and nitrogen compounds have much in common.[1][2]

Phosphorus can adopt valency λ. In this system a phosphine is a δ3λ3 compound.

Phosphanes & phosphines

The parent compound of the phosphanes is PH3, called phosphine in the US and UK and phosphane elsewhere.[3] Replacement of one or more protons by an organic residue, gives PH3−xRx, an organophosphine or organophosphane, again depending on the country. The phosphorus atom in phosphanes/phosphines has a formal oxidation state −3 (δ3λ3) and are the phosphorus analogues of simple amines.

An often used organic phosphine is cone angle.

The barrier to inversion is also much higher than in amines for a process like substituents can display optical isomerism.

The basicity of phospines is less than that of corresponding amines, for instance phosphonium ion itself has a trimethylamine; and triphenylphosphonium (pKa 11.2) is less basic than triphenylammonium (pKa 19).

Amines and phosphines both have a aromatic.

The reactivity of phosphines match that of amines with regard to nucleophilicity in the formation of Appel reaction converting alcohols to alkyl halides.

A difference in reactivity with amines is the ease of oxidation of phosphines to phosphine oxides.

Synthesis

Synthetic produces for phosphines are:

  • peroxides to give anti-Markovnikov adducts.
  • alkynes in presence of base. Secondary phosphines react with electron-deficient alkynes such as phenylcyanoacetylene without base.
  • chlorosilane.

Reactions

The main reaction types of phosphines are:

Phosphines are reaction mechanism the first proton is on loan from the methyl group in trimethylphosphine (triphenylphosphine does not react).
When modified with suitable substituents as in certain diazaphospholenes (scheme 3) the polarity of the P-H bond can actually be inverted (see: benzophenone in yet another way.[6]
  • Multidentate phosphines such as ligands in organometallic chemistry.

Phosphanes

Primary phosphanes are under-used in chemistry due to their general lack of stability towards oxygen. One study[7] reports on several novel air-stable aromatic primary phosphanes prepared by phosphonate:

The stability is attributed to lone pair.

Phosphine oxides

Phosphine oxides (designation δ3λ3) have the general structure R3P=O with formal oxidation state −1. Phospines form hydrogen bonds and many phosphines are therefore soluble in water. The P=O bond is very polar with a dipole moment of 4.51 D for triphenylphosphine.

The nature of the phosphorus to oxygen double bond is a matter of debate. Pentavalent phosphorus like nitrogen is not compatible with the Molecular Orbital Theory proposes that the short bond length is attributed to the donation of the lone pair electrons from oxygen to the antibonding phosphorus-carbon bonds. This proposal is supported by ab initio calculations and has gained consensus in the chemistry community.

Phospines are easily oxidized to phosphine oxides as examplified by the directed synthesis of a phospha crown, the phosphorus analogue of an aza crown[8] where it is not possible to isolate the phosphine itself.[9]

Phosphonates

bisphosphonates are a class of drugs.

Phosphite and phosphate esters

plasticizers. Lacking a P−C bond, these compounds are technically not organophosphorus compounds.

Phosphoranes

Wittig reaction.

Phosphorus multiple bonds

Many compounds exist with carbon phosphorus multiple bonds (P=C) as phosphaalkenes (R2C::PR) and phosphaalkynes (RC:::PR). In the compound Diels-Alder reactions.

The first phosphaalkene was synthesised in 1974 by Becker as a Brook rearrangement:

with R = methyl or phenyl and tms representing trimethylsilyl.

In the same year Harold Kroto established spectroscopically that thermolysis of Me2PH yielded CH2=PMe.

A general method for the synthesis of phosphaalkenes is by triethylamine:

The Becker method is used in the synthesis of the phosphorus pendant of Poly(p-phenylene vinylene):[10]

Phosphazenes have a P=N double bond.

See also

CH He
CLi CBe CB CC CN CO CF Ne
CNa CMg CAl CSi CP CS CCl Ar
CK CCa CSc CTi CV CCr CMn CFe CCo CNi CCu CZn CGa CGe CAs CSe CBr Kr
CRb CSr CY CZr CNb CMo CTc CRu CRh CPd CAg CCd CIn CSn CSb CTe CI Xe
CCs CBa CHf CTa CW CRe COs CIr CPt CAu CHg CTl CPb CBi CPo CAt Rn
Fr Ra Rf Db Sg Bh Hs Mt Ds Rg Uub Uut Uuq Uup Uuh Uus Uuo
↓
La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Ac Th Pa CU Np Pu Am Cm Bk Cf Es Fm Md No Lr


carbon
Core organic chemistry many uses in chemistry.
Academic research, but no widespread use Bond unknown / not assessed.

References

  1. ^ Dillon, K. B.; Mathey, F.; Nixon, J. F. Phosphorus. The Carbon Copy; John Wiley & Sons, 1997. ISBN 0-471-97360-2
  2. ^ Quin, L. D. A Guide to Organophosphorus Chemistry; John Wiley & Sons, 2000. ISBN 0-471-31824-8
  3. ^ Gold Book: Link
  4. ^ Arbuzova, S. N.; Gusarova, N. K.; Trofimov, B. A. "Nucleophilic and free-radical additions of phosphines and phosphine chalcogenides to alkenes and alkynes." Arkivoc 2006, part v, 12–36 (EL-1761AR). Article
  5. ^ Zhang, W.; Shi, M. "Reduction of activated carbonyl groups by alkyl phosphines: formation of α-hydroxy esters and ketones." Chem. Commun. 2006, 1218–1220. doi:10.1039/b516467b
  6. ^ Burck, S.; Gudat, D.; Nieger, M.; Du Mont, W.-W. "P-Hydrogen-Substituted 1,3,2-Diazaphospholenes: Molecular Hydrides." J. Am. Chem. Soc. 2006, 128, 3946–3955. doi:10.1021/ja057827j
  7. ^ Taming a Functional Group: Creating Air-Stable, Chiral Primary Phosphanes Rachel M. Hiney, Lee J. Higham, Helge Müller-Bunz, Declan G. Gilheany Angewandte Chemie International Edition Volume 45, Issue 43 , Pages 7248 - 7251 2006 doi:10.1002/anie.200602143
  8. ^ Edwards, P. G.; Haigh, R.; Li, D.; Newman, P. D. "Template Synthesis of 1,4,7-Triphosphacyclononanes." J. Am. Chem. Soc. 2006, 128, 3818–3830. doi:10.1021/ja0578956
  9. ^ In step 1 diphosphinoethane coordinates to a bromine but oxidation of the phosphine groups is unavoidable
  10. ^ Phosphorus Copies of PPV: -Conjugated Polymers and Molecules Composed of Alternating Phenylene and Phosphaalkene Moieties Vincent A. Wright, Brian O. Patrick, Celine Schneider, and Derek P. Gates J. Am. Chem. Soc.; 2006; 128(27) pp 8836 - 8844; (Article) doi:10.1021/ja060816l
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Organophosphorus". A list of authors is available in Wikipedia.