Tetramers phosphorus compounds

Many other aliphatic or aromatic amines produce the same reaction. However if N-alkyl (or aryl)2-aniline is made to react with tris-dimethylaminophosphine, tricoordinated phosphorus compounds are obtained. Their analyses and mass spectra show that they are tetramers (5) when the energy of the ionizing electron beam is nearly 70 eV the mass spectra of the oligomers show an intense [M] peak which corresponds to the monomer ion (n = 1) but when the spectra are obtained by field desorption m.s. the molecular ion peak corresponds to a tetramer (n = 4) one sees also smaller peaks for ions n = 3, 2 or 1. 

Phosphorus Compounds. - The synthesis of the chiral phosphate (494) has been described. The silyl ether ds-Me3SiOCMe=CMeOSiMe3 reacts with Me0P(0)p3 to yield the dioxaphospholen (495). Treatment of the tetramer (496) with boron trifluoride affords the di-co-ordinated phosphorus compound (497). The imines (499) are obtained when the 1,2,3-diaza-phospholine (498) is heated with aryl azides. The oxazaphospholine (500) decomposes to trimethyl phosphate and the nitrile ylide (CF3)2C-N=CPh. ... 

The question of whether the phosphonitrilic chlorides have cyclic or linear structures has been frequently discussed in the literature. The structural evidence will be considered in Section lY, where it will be seen that the cyclic formulation is established beyond doubt for the trimer and tetramer, and is highly probable for the higher soluble polymers it will meanwhile be assumed for all compounds of formula (PNX2) . For reasons considered in Section II, C the petrol-insoluble fraction (PNCUln PCls is believed to consist of a mixture of linear polymers. The two series are related, in that the linear compounds of low molecular weight are intermediates in the formation of the cyclics by the ammonolysis of phosphorus pentachloride. 

Phosphorus-containing cubanes of the type (RMPR )4 (M=A1, Ga, In) have been prepared by alkane elimination or salt eliinination methods. The new compounds have been characterized by X-ray crystallography, NMR, and mass spectroscopy. Conceptually, the group 13/15 cubanes can be regarded as tetramers of RM=PR . If the steric bulk of the substituents R and R is increased it is possible to isolate dimers, (RMPR )2. 

Structure X-ray examination reveals that the trimer and tetramer chlorophosphazenes are having the six and eight membered rings and composed of alternate nitrogen and phosphorus atoms. Thus these compounds may be regarded as the phosphorus-nitrogen analogues of benzene and cyclo-octatetraene... 

The phosphazenes are cyclic or chain compounds that contain alternating phosphorus and nitrogen atoms with two substituents on each phosphorus atom. The three main structural types are the cyclic trimer (13-11), cyclic tetramer (13-III) and the oligomer or high polymer (13-IV). A few cyclic pentamers and hexamers are also known. The alternating sets of single and double bonds in (13-11) to (13-IV) are written for convenience but (see below) should not be taken literally. 

Abstract Phosphacumulene ylides of the general formula Ph3P=C=C=X [X=0, S, NR, (0R)2] are versatile C2-building blocks. They can act either as C-nudeophiles-only in a manner typical of phosphorus ylides, or as cumulenes undergoing [2 + n -cycloadditions with other cumulenes such as CO2, COS, RNCO etc. Most prominent is their tandem addition-Wittig alkenation of hydroxy- or amino-substituted carbonyl compounds. With aptly chosen reaction partners all these pathways may lead to heterocyclic products. Some recent applications of these methods to the syntheses of azetidines, five-membered lactams, lactones, tetramates, tetronates and pyrroles as well as to six-membered quinolones and to macrolides are delineated. 

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