Organophosphides

Sodium and potassium organophosphide reagents continue to be employed in the synthesis of new phosphines. The tetradentate... 

The synthesis of alkali metal organophosphides and arsenides is usually most conveniently achieved by the direct metalation of a primary or secondary phosphine/arsine with a strong deprotonating agent such as an alkyllithium or an alkali metal hydride ... 

This is the most widely used route to alkali metal (di)organophos-phide complexes. The alkali metal (di)organophosphide products are highly air and moisture sensitive and must be handled under an inert atmosphere. Alternative routes to these compounds include the following ... 

Access to heavier alkali metal complexes may also be achieved by metathesis between a lithium organophosphide and a heavier alkali metal alkoxide (27) ... 

Selected Structural and NMR Data for Crystallographically Characterized Lithium (Di)organophosphide Complexes... 

Compared to the wealth of data concerning the solid- and solution-state structures of lithium (di)organophosphides, reports of heavier alkali metal analogues are sparse. Indeed, the first crystallographic study of a homometallic heavier alkali metal (di)organophosphide complex was reported only in 1990 (67) and the majority of such complexes have been reported in the past 3 years. Interest in these complexes stems mainly from their enhanced reactivity in comparison to equivalent lithium complexes, which is particularly useful for the synthesis of alkaline earth, lanthanide, and actinide organophosphide complexes. 

In comparison to alkali metal complexes of (di)organophosphide ligands, complexes of these metals with (di)organoarsenide ligands are relatively rare and few have been structurally characterized. This dearth of structural information is perhaps due in part to the relatively low importance of such complexes in inorganic and organic synthesis and to the lower stability (both thermal and photolytic) of arsenide complexes compared to their phosphide analogues. 

Synthesis of lithium (di)organoarsenide complexes is achieved by similar methods to those outlined for organophosphide complexes (see Section I,A,1) and include (i) deprotonation of a primary or secondary arsenide with a strong base such as BuLi or LiAsH2, (ii) As-Si cleavage using BuLi, or (iii) reaction of a chloroarsine with lithium. 

As has been observed for (di)organophosphide complexes of the alkali metals, the structures and aggregation states of alkali metal phosphinomethanide s are dramatically affected by the size and nature of the ligand substituents and the presence of additional coligands such as THF, tmeda, or pmdeta. The subtle interplay of these factors, and in particular the steric and electronic properties of substituents at both phosphorus and the a-carbon, defines the structures adopted by such complexes. 

Two reports of the hitherto little documented attack of organophosphide anions on halogen have appeared. Addition of 1,2-dibromoalkenes to lithium diphenyl-phosphide in THF gives an acetylene and tetraphenyldiphosphine81 (Scheme 1). 

Biphosphines may be formed by several methods involving the treatment of phosphinous halides with either electropositive metals or organomercury compounds. An additional intriguing approach involves the reaction of metal organophosphides (see Section 3.2) with 1,2-dibromoethane to form the phosphorus-phosphorus bond and extrude ethylene (equation 17). 

A number of organophosphides and organoarsenides of divalent lanthanides have been synthesised, with a certain similarity to the amides. [Ybl2(thf)2] and [Yb N(SiMe3)2 2(thf)2] react with KPPh2 forming [Yb(PPh2)2(thf)4] the thf can be displaced by iV-methylimidazole form-... 

From the DjO-Ca P reaction, P2D4 is obtained also. When treated with D O alkali-metal organophosphides produce deuteriophosphines in high yields (>75%) and isoto-pically pure, e.g. ... 

Sodio-organophosphine reagents have also found considerable use in the past years. Aminyl radicals, R2N, are involved in the photo-assisted radical-nucleophilic substitution reactions between sodium diphenylphosphide and N-cyclopropyl-A-ethyl-/ -toluenesulfonamide in liquid ammonia, which after oxygenation, leads to the aminoalkyldiphosphine dioxide (80) as the principal product. The reactions of sodio-organophosphide reagents with chloroalkyl... 

Potassium organophosphide reagents also continue to find applications in synthesis. Direct displacement of fluoride from fluoroaromatic substrates by potassium diphenylphosphide is the key step in the synthesis of the phosphi-noarylsulfoxides (88), water-soluble phosphino-amino acid systems, e.g. (89), ° and the chiral benzoxazine system (90). Related displacement of fluoride by potassium monophenylphosphide has been used to prepare a series of hydrophilic triarylphosphines, e.g. (91). Among new phosphines prepared by conventional displacement reactions by potassium diphenylphosphide on... 

The synthesis and characterisation of organophosphide derivatives of other metallic elements continues to attract attention, and the past year has seen further examples of systems involving aluminium , galliumindium " titanium", and zirconium" ". In addition, organophosphide derivatives of niobium , tantalum" , and samariumhave also been described. 

White phosphorus also reacts with carbon nucleophiles in ether or tetrahydrofuran to give dark red solutions believed to be complex organophosphides (Rauhut and Semsel). Hydrolysis of a mixture obtained from reactions of white phosphorus with organolithium and organomagnesium compounds gives the primary phosphine as the major product, with small amounts of secondary and tertiary phosphines being formed under some conditions. 

From Metallated Phosphines. The reactions of organophosphide anions with alkyl tosylates have been used to prepare the chiral diphosphines (12) and (13), and also a range of phosphines bearing chiral substituents derived from various natural products. ... 

As in recent years, the synthesis of new chiral phosphines and related chiral tervalent phosphorus esters and amides continues to be a major preoccupation, being driven by the need for improved performance in metal-catalysed processes. It is very pleasing to note that two of the recipients of the 2001 Nobel Prize for Chemistry, William S. Knowles, and Ryoji Noyori, are honoured for their work in the synthesis and application in catalysis of chiral phosphine ligands. Interest in the structures of metallo-organophosphide systems, noted in the previous volume, has continued to develop. The chemistry of heteroaromatic ring systems, notably that of phospholes, and of low coordination number p -bonded compounds, also remain active areas. 

---