Tertiary phosphine chalcogenides

Tertiary phosphine sulfides are generally stable compounds and are not easily oxidised by air, although they can be oxidised by hydrogen peroxide or dilute nitric acid. The analogous tertiary phosphine selenides and tellurides are however, more reactive to oxidation. Similar to the sulfides they can be prepared from the direct reaction of elemental chalcogen with a tertiary phosphine (Equation 1). Tertiary phosphine selenides are also accessible from tertiary phosphines using KSeCN as the selenium source instead of the element itself. 

Studies on the solid-state structures, vibrational frequencies and dipole moments of tertiary phosphine chalcogenides have shown the phosphorus to be in an approximately tetrahedral environment with phosphorus-chalcogen bond lengths in-between those expected for single and double bonds.21 There has been much debate on the nature of the phosphorus-chalcogen bond in these 

Ph3PS + CH3U phH Ph2P(S)CH2Li + Ph2P(S)CH2PPh2 (7) 

The mono- and di-chalcogenides of dppm contain an acidic methylene carbon which can undergo deprotonation. NMR spectroscopic studies on the relative acidities of these methylene groups show an increase in acidity for the series R2PCH2PR2 R2P(0)CH2P(0)R2 R2P(S)CH2P(S)R2  

Related to these diphosphine dichalcogenides are the triphosphine trisulfides [R2P(S)]3CH (12) which can be prepared from lithiated methylene diphosphine disulfides upon treatment with thiophosphinic chlorides (Equation 9). Deprotonation of 12 with tBuLi gives a resonance-stabilised anion 13 containing a planar central carbanion whose charge is delocalised onto the three neighbouring phosphorus and sulfur atoms.32 

Other related compounds are the diphosphine disulfides R2P(S)P(S)R2 14, which contain a direct phosphorus-phosphorus bond, and polysulfur Ai5(dior-ganophosphine sulfides) R2P(S)-S -P(S)R2 in which the two phosphorus centres are connected by a chain of one of more sulfur atoms. R2P(S)P(S)R2 compounds are accessible from heating secondary phosphine sulfides with thiophosphinic chlorides (Equation 10) or by reaction of Awphosphines with 

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Tertiary phosphine chalcogenide Diphosphine dichalcogenide Diphosphine monochalcogenide... 

P=S and P=Se bonds. There is also the question of the ease of removal of the element Z to leave behind a tervalent phosphorus compound. This topic has already been considered in the case of the tertiary phosphine chalcogenides. ... 

Trofimov et al. prepared secondary phosphine chalcogenides with ary-lethyl- or hetarylethyl substituents and utilized them in the synthesis of tertiary phosphine chalcogenides containing a furyl group in on of the alkyl substituents (Scheme 22). ... 

Lanthanide-, tellurium(Il)- and tellurium(IV), as well as, cadmium(II) and zink(II) complexes of tertiary phosphine chalcogenides were also described. ... 

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