Phosphorus and Arsenic Compounds

Biswas and recently found that N-vinylcarbazole can be polymerised by 

The authors reported that about 90% of the oligomers obtained contained a magnesium atom, a fact which strongly favours their proposed initiation mechanism. 

Biswas and Mishra reported that arsenic trichloride can initiate the polymerisation of a-methylstyrene in benzene and methylene chloride at 25°C. No exhaustive study was made of this system. The same authors also reported that PCI3, PBra and POCI3 are effective initiators for the polymerisation of a-methylstyrene, particularly in nitrobenzene. The latter catalyst was selected for a more detailed investigation water was considered as detrimental to initiation, which was postulated to occur directly as 

Taninaka et al. recently published a rimilar study on the polymerisation of styrene by roCls. Although S-shaped conversion-time curves were obtained, the maximum rate 

Like tertiary amines, tertiary phosphines are readily transformed into the corresponding oxides, phosphine oxides. Tributylphosphine in di-chloromethane is oxidized with ozone adsorbed on silica gel at -70 C to tributylphosphine oxide in 92% yield [113]. Other oxidants used to transform phosphines into phosphine oxides are potassium peroxysulfate [205], argentic oxide [381 ], manganese dioxide [813], and barium manganate [S55] (equation 537). 

A similar oxidation of trivalent phosphorus to pentavalent phosphorus occurs in trialkyl or triaryl phosphites. Triphenyl phosphite is converted by ozone in dichloromethane at 5-10 C into triphenyl phosphate in 95% yield [775] and by argentic oxide in 30% yield [557] (equation 538). 

The oxidation of phosphites to phosphates is very important in the chemistry of nucleoside phosphites, which must be handled under anhydrous conditions. For this purpose, anhydrous hydrogen peroxide bis(trimethylsilyl) peroxide, cumene hydroperoxide, and iV-methylmor  

Trialkyl and triarylphosphine oxides are also prepared by oxidation of trialkyl and triarylphosphine sulfides and selenides (equation 540) [1007, 1194]. 

The same oxidation procedures apply to the conversion of trialkyl or triaryl thiophosphates and selenophosphates into phosphates [1007, 1194] (equation 541). 

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Besides the thiocyanates, just mentioned, other 5-donor complexes which are of interest are the dialkyl sulfides, [MCl3(SR2)3], produced by the action of SR2 on ethanolic RhCl3 or on [IrClg] ". Phosphorus and arsenic compounds are obtained in similar fashion, and the best known are the yellow to orange complexes, [ML3X3], (M = Rh, Ir X = Cl, Br, I L = trialkyl or triaryl phosphine or arsine). These compounds may exist as either mer or fac isomers, and these are normally distinguished by their proton nmr spectra (a distinction previously made by the measurement of dipole moments). An especially... 

The preparation of similar precursors suitable for the deposition of metal nitrides is analogous to the preparations of phosphorus and arsenic compounds. The initial reaction of metal trialkyls MR3 (M = A1, Ga, In) with amines (NHR 2) results in the formation of oligomeric amido compounds [R2MNR 2] (n = 2 or 3) which eliminate alkanes on thermolysis. The incorporation of a proton as a substituent on the pnictide bridging ligand has been examined, and many compounds of the type [R2MNHR ]2 have been synthesized. The presence of this proton may facilitate /3-elimination, allowing lower deposition temperatures to be used. 

Pyridyl-phosphorus and -arsenic compounds have also been made by nucleophilic displacement reactions with, for example, 3-pyridinediazonium salts (74HC(14-2)489). Organomercury derivatives can be converted into bromides and iodides by standard methods, e.g. Scheme 147 (59JPR(8)156). 

Limpid octahedra, isomorphous with the corresponding phosphorus and arsenic compounds.6... 

All attempts to prepare a spirocyclic hexacoordinate antimonate complex 168 and a tetracoordinate spirostibonium ion 167 or onium-ate combinations of these, according to structural and synthetic principles elaborated with corresponding phosphorus and arsenic compounds, met with failure138). When, for example,-... 

In a series of nitrogen, phosphorus, and arsenic compounds differences in their mass spectra (75) may be attributed to the differing abilities of the heteroatoms to stabilize positive charges of the atoms themselves or... 

The silyl phosphorus and arsenic compounds react with a variety of reagents and form adducts more readily with Lewis acids than the silyl amines (Scheme 57). ... 

Parent Acid Names Used in Functional Replacement Nomenclature of Phosphorus and Arsenic Compounds... 

Sulfur, Phosphorus, and Arsenic Compounds. Sulfur, occasionally present in synthesis gases from coal or heavy fuel oil, is more tightly bound on iron catalysts than oxygen. For example, catalysts partially poisoned with hydrogen sulfide cannot be regenerated under the conditions of industrial ammonia synthesis. Compounds of phosphorus and arsenic are poisons but are not generally present in industrial synthesis gas. There are... 

Several reviews encompassing a number of aspects of the inorganic chemistry of Group V elements have appeared. These include surveys of X-ray diffraction studies of a number of N, P, As, Sb, and Bi compounds, the stereochemistry of compounds containing Si—N, P—N, S—N, and Cl—N bonds, and ESCA-derived group shifts for a substantial number of nitrogen, phosphorus, and arsenic compounds. The latter describe the experimental shifts to within 0.5 eV, and facilitate the predictive and analytical use of ESCA. ... 

Pentaphenylarsenic has been found to be isomorphous with penta-phenylphosphorus 419) although different from pentaphenylantimony which has the unusual square pyramidal arrangement of ligands. The initial communication suggested that the phosphorus and arsenic compounds also have a square pyramidal structure, however, since penta-phenylphosphorus has now been found to have the trigonal bipyramid structure 420) it can be expected that this arrangement also exists in pentaphenylarsenic. 

If radicals are formed in solution, what happens upon vaporization Around this time, studies of the gas-phase structures of the phosphorus and arsenic compounds were initiated in two separate gas electron diffraction (GED) laboratories. It was soon clear that in both cases the compounds were effectively 100% dissociated in the gas phase. However, determination of the molecular structures of the P[CH(SiMe3)2]2 and As[CH(SiMe3)2]2 radicals was a very difficult undertaking as in GED studies resolution of similar interatomic distances is difficult if not impossible. In P[CH(SiMe3)2]2 there are P—C distances and inner and outer Si—C distances, which are aU nearly the same, and there are similar problems with non-bonded distances, P Si, Si Si and C C. In As[CH(SiMe3)2]2 the problems are essentially the same. There are also distortions due to steric crowding, and the molecules have little symmetry (C2 in the gas phase). 

Sulfide ions, selenium, phosphorus, and arsenic compounds increase the likelihood of hydrogen stress cracking. Their presence should warn of a possible failure. 

In general, any compound that can lower the surface tension of iron may be considered as a poison [9]. Phosphorus and arsenic compounds are also known as permanent poisons [1]. However, in the natural gas-based plants they are rare and only found in exceptional cases. A catalyst prepared with 1-3 wt% P2O5 was examined and found to be severely poisoned [10]. Chlorine [1] is a serious poison that reacts with the potassium promoter and forms potassium chloride which is slightly volatile and consequently removed from the catalyst surface. It is expected that other halogens behave similarly [1]. Calculations show that ppb amounts in the synthesis gas should result in a marked deactivation [2]. 

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