1,3,2,4-Dithiadiphosphetane 2,4-disulfides
3030168
186760731
2008-01-25T05:49:55Z
GngstrMNKY
5517145
/* Examples */
[[Image:Fp2P2S4-3D-balls.png|thumb|right|200px|[[Ball-and-stick model]] of Fc<sub>2</sub>P<sub>2</sub>S<sub>4</sub>, ''diferrocenyl 1,3,2,4-dithiadiphosphetane 2,4-disulfide'']]
'''1,3,2,4-Dithiadiphosphetane 2,4-disulfides''' are a class of four-membered ring [[Chemical compound|compounds]] which contain a P<sub>2</sub>S<sub>2</sub> ring, many of these compounds are able to act as sources of the dithiophosphine [[ylide]]s. The most well known example of this class of compound is [[Lawesson's reagent]].
Other examples of this class of compound have been made; many inorganic chemists are now using Fc<sub>2</sub>P<sub>2</sub>S<sub>4</sub> (Fc = [[ferrocene]]) as a starting material in reactions investigating the general chemistry of the 1,3,2,4-dithiadiphosphetane 2,4-disulfides, one reaction for this is that the Fc<sub>2</sub>P<sub>2</sub>S<sub>4</sub> compound and all its derivatives are red which make column chromatography of the products more easy. Also the ferrocenyl groups provide an electrochemical handle which provide another means of investigating the properties of the products.
==Examples==
While several different routes to the 1,3,2,4-dithiadiphosphetane 2,4-disulfides exist the most commonly used is the [[electrophilic]] [[aromatic]] substitution reaction of an arene with P<sub>4</sub>S<sub>10</sub>. An alternative reaction is the reaction of a [[thiol]] with P<sub>4</sub>S<sub>10</sub> to form a substance like the [[Davy reagent]]. The Davy reagent is identical to Lawesson's reagent except in place of the para-methoxyphenyl groups it has aryl sulfide groups. While the Davy reagent is more soluble than the Lawesson's reagent it is likely that the very [[vile]] nature of the [[thiol]] starting material is likely to make the synthesis of this compound not worth the trouble.{{Fact|date=September 2007}} In both the [[patent]] and [[academic]] chemical literature are examples of 1,3,2,4-dithiadiphosphetane 2,4-disulfides with higher solubilities.{{Fact|date=September 2007}} These highly soluble versions of Lawesson's reagent are created by the reaction of P<sub>4</sub>S<sub>10</sub> with aryl [[ethers]] which are different from [[anisole]]. For instance butoxybenzene and 2-tert-butylanisole have both been reacted to form more soluble thionation reagents of the 1,3,2,4-dithiadiphosphetane 2,4-disulfide class.
[[Image:dithia.png|left|thumb|The general structure of a 1,3,2,4-dithiadiphosphetane 2,4-disulfide and the reversible generation of the dithiophosphine ylides]]
An important subclass of these compounds are the [[naphthalen-1,8-diyl 1,3,2,4-dithiadiphosphetane 2,4-disulfide]]s; these are intellectually interesting because the two dithiophosphine ylides are fixed together in space by the rigid napthalene unit. The reactivity of these compounds is very different from that of 1,3,2,4-dithiadiphosphetane 2,4-disulfides.
==Reactions==
The dithiophosphine ylides are normally attacked at the phosphorus atom by a [[nucleophile]], for instance the reaction of an [[alkoxide]], [[phenolate]], [[alcohol]] or [[phenol]] with a 1,3,2,4-dithiadiphosphetane 2,4-disulfide can form a new compound with a [[phosphorus]]-[[oxygen]] bond. Such a reaction has been used in the formation of metal binding agents and in the synthesis of [[insecticide]]s.
[[Image:LRnucleophileelectrophile.png|thumb|The reaction of a 1,3,2,4-dithiadiphosphetane 2,4-disulfide with either a nucleophile or an electrophile]]
The reaction of an [[electrophile]] with 1,3,2,4-dithiadiphosphetane 2,4-disulfides is less common, but the reaction of an [[alkyl]] [[halide]] with a 1,3,2,4-dithiadiphosphetane 2,4-disulfide forms a new compound with a [[sulfur]]-[[carbon]] [[Chemical bond|bond]] and a [[phosphorus]]-[[halide]] bond. Such a compound could act as an [[acetylcholinesterase]] [[Enzyme inhibitor|inhibitor]] in insects, but in order to make a better [[insecticide]] it would be best to convert the halide to another [[leaving group]] which would form a less water sensitive product. For instance the reaction of para-nitrophenolate would form a compound similar to [[parathion]].
Lawesson's reagent has been used as a starting material for a [[herbicide]] by reaction with a 1-alkoxy-2,3-dihydroxy propane. This formed a compound which could be used to kill plants. This reaction of a 1,2-diol with lawesson's reagent results in a [[symmetric]] breaking of the P<sub>2</sub>S<sub>2</sub> ring, both halves of the lawesson's reagent end up being converted to the same product.
A different type of ring breaking reaction can occur when LR is reacted with a metal compounds such as a platinum dichloride bis-phosphine complex, in this case one molecule of MeOC<sub>6</sub>H<sub>4</sub>P(S)Cl<sub>2</sub> is formed as a side product to the platinum complex ([Pt(S<sub>2</sub>P(S)C<sub>6</sub>H<sub>4</sub>OMe)(PR<sub>3</sub>)<sub>2</sub>]).{{Fact|date=September 2007}}
Lawesson's reagent can be used as a dehydrating reagent, for example it has been used to convert a β-aminoamide into an imidazoline.
Another useful reaction of LR is the conversion of a 1,4-diketone into a thiophene ring, this reaction can be done with P<sub>4</sub>S<sub>10</sub> but a much higher temperature would be required to make it work with P<sub>4</sub>S<sub>10</sub>.
It was claimed in a German patent{{Fact|date=September 2007}} that the reaction of 1,3,2,4-dithiadiphosphetane 2,4-disulfides with dialkyl cyanamides formed plant protection agents which contained six-membered (P-N=C-N=C-S-) rings. It has been proven in recent times by the reaction of diferrocenyl 1,3,2,4-dithiadiphosphetane 2,4-disulfide (and Lawesson's reagent) with dimethyl [[cyanamide]] that in fact a mixture of several different [[phosphorus]] containing compounds is formed. Depending on the concentration of the dimethyl cyanamide in the reaction mixture either a different six membered ring compound (P-N=C-S-C=N-) or a nonheterocylic compound (FcP(S)(NR<sub>2</sub>)(NCS)) is formed as the major product, the other compound is formed as a minor product.
[[Image:FcPthiocyanate2.jpg|left|thumb|One of the products of the reaction of Fc<sub>2</sub>P<sub>2</sub>S<sub>4</sub> with dimethyl cyanamide]]
In addition small traces of other compounds are also formed in the reaction. It is unlikely that the ring compound (P-N=C-S-C=N-) {or its isomer} would act as a plant protection agent, but (FcP(S)(NR<sub>2</sub>)(NCS)) compounds can act as [[nerve]] poisons in [[insects]]. These compounds bearing terminal [[sulfur]] atoms on the [[phosphorus]] atom are much less toxic than the compounds (such as [[sarin]], [[VX (nerve agent)|VX]] and [[tetraethyl pyrophosphate]]) which have an [[oxygen]] in place of this terminal sulfur. This is because the P=S compound is not active as an [[acetylcholinesterase]] [[Enzyme inhibitor|inhibitor]] in either [[mammals]] or insects, in mammals the animals [[metabolism]] tends to remove [[lipophilic]] side groups from the phosphorus atom while an insect tends to [[oxidise]] the compound so removing the terminal sulfur and replacing it with a terminal oxygen which causes the compound to be more able to act as an acetylcholinesterase inhibitor.
[[Image:FcNorb.jpg|thumb|The structure of the PSC<sub>2</sub> compound]]
The dithiophosphine ylides of LR and related compounds can react with strained alkenes, for example the bicyclic norbornadiene reacts with Fc<sub>2</sub>P<sub>2</sub>S<sub>4</sub> to form a compound with a PSC<sub>2</sub> ring. Unlike small rings containing only first row elements such as [[carbon]], [[nitrogen]] and [[oxygen]] the small rings containing more heavy elements such as [[sulfur]] and [[selenium]] are more stable with regards to ring opening. Hence, the rings such as PSC<sub>2</sub> are much more stable than things like [[epoxides]].
A selenium version of this ring type has been made, one notable example has been named [[Woollins reagent]] and is Ph<sub>2</sub>P<sub>2</sub>Se<sub>4</sub>, this is made by the reaction of (PhP)<sub>5</sub> with [[selenium]] metal. The solubility of this compound is very low but the group of Prof J. Derek Woollins have published some reactions of this compound. For instance the reaction of '''Woollins''' reagent (WR) with a dialkyl cyanamide has been found to form a bicyclic PC<sub>2</sub>N<sub>2</sub>Se<sub>3</sub> system.
==References==
{{Unreferenced|date=September 2007}}
<references/>
[[Category:Organosulfur compounds|Dithiadiphosphetane 2,4-disulfides, 1,3,2,4-]]
[[ja:1,3,2,4-ジチアジホスフェタン 2,4-ジスルフィド]]