Phosphorus systems

Schoeller WW (2003) Donor-Acceptor Complexes of Low-Coordinated Cationic p-Bonded Phosphorus Systems. 229 75-94... 

Keywords. Cations, n-Bonded, Low-coordinated phosphorus systems. Donor-addition, Mono-and bis-coordination, Bipyramide formation... 

Donor-Acceptor Complexes of Low-Coordinated Cationicn-Bonded Phosphorus Systems... 

The third chapter (W.W. Schoeller) reviews the latest developments in the area of donor-acceptor complexes of low coordinated cationic n-bonded phosphorus systems, a topic which attracts the interest of many researchers, both from theoretical and experimental points of view. 

The chemistry of three coordinate pentacovalent phosphorus systems continues to develop. Various routes to the three coordinate phosphoranes (197) have been described. As a result of... 

Quin LD (1981) The heterocyclic chemistry of phosphorus systems based on the phosphorus-carbon bond. Wiley, New York... 

PMMA - Red Phosphorus System. The initial reaction that was investigated was that between PMMA and red phosphorus (4-51. Phosphorus was chosen since this material is known to function as a flame retardant for oxygen-containing polymers (1 2). Two previous investigations of the reaction of PMMA with red phosphorus have been carried out and the results are conflicting. Raley has reported that the addition of organic halides and red phosphorus to PMMA caused moderate to severe deterioration in flammability characteristics. Other authors have reported that the addition of chlorine and phosphorus compounds are effective flame retardant additives (12). 

An important advantage in phosphorus systems is the fact that 31P, which is the only natural isotope, has a spin of and can be easily measured by NMR. Its characteristic chemical shifts 8 (p.p.m.) and its H and 13C coupling constants J (Hz) have influenced the development of the heterocyclic chemistry of phosphorus more than any other physical methods such as IR, UV, MS, dipole moment measurement and others. 

This type of reaction is very common in the nitrogen equivalent pyridine system (the ready formation of enamines and the ready availability of 1,3-electrophiles, such as acrolein and their equivalents). With the phosphorus system, the not so common enamine equivalent makes it a not so common synthetic approach. However, with proper substituents 1,3-dinucleophilic P-C(2) fragments have been reacted with 1,3-electrophiles, and have been used in the synthesis of As-phosphinolines <1996CHEC-II(5)639>. 

At the time of writing, therefore, we can conclude that, whereas in carbon systems there is firm evidence for a phenomenon of some sort which demands rationalisation, in phosphorus systems no such evidence exists. 

A notable feature in all these coupling protocols is that the coupling rates of iron-phosphorus systems, of the (salen)iron complex 5, the Fe(acac)3 catalyst, and catalyst 10 with respect to the alkyl halide are rather uncommonly bromide> iodide>chloride (entries 3, 4, 9, 13), whereas the reactivity order for iron-amine catalyst systems is iodide>bromide>chloride (entries 1, 5, 6). 

The crystal and molecular structures of two spiroarsoranes of type XXI (R = Ph, R = R" = CH3 and R = OH, R = R" = H) have been determined by single-crystal X-ray diffraction analyses (68, 69). The crystal data for these compounds are summarized in Table V. Both compounds have a geometry at the arsenic atom that lies on the Berry coordinate between rectangular-pyramidal and trigonal-pyramidal. These structures show close parallels between the structures of related arsenic and phosphorus systems. It has been concluded that, since the solid-state structures of these compounds lie close to the Berry coordinate, the dynamic process in solution is distortion along that coordinate (68, 69). 

Upon undertaking chemistry of phosphorus systems, the question of characterization of reaction products comes to the fore. In addition to X-ray crystallography, which has been absolutely invaluable in many situations, P mm and infrared spectroscopy are routinely applied to phosphorus systems. Figme 2 and Figme 3 provide some indicative chemical shifts (on the basis of the standard phosphorus reference, namely 85% aqueous phosphoric acid) and stretching frequencies that result from these techniques. 

More cost/performance effective than halogen/antimony oxide or other halogen/phosphorus systems... 

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