Reactions of elemental phosphorus and phosphine with electrophiles in superbasic systems: XVIII. Phosphorylation of 1-(chloromethyl)naphthalene with the elemental phosphorus

1-Chloromethylnaphthalene reacts with white and red phosphorus, and also with the “activated red phosphorus,” the complex organophosphorus polymer of unknown structure obtained by irradiation of a solution of white phosphorus in benzene by the ⁶⁰Co source, in a system including KOH water solution, dioxane or benzene, and a phase transfer catalyst (22–98°C, argon), to form bis(1-naphthylmethyl)-and tris-(1-naphthylmethyl)phosphine oxides, and also (1-naphthylmethyl)phosphonous-and bis(1-naphthylmethyl)-phosphinic acids. The yield and the ratio of the reaction products depend on reaction conditions as well as on the nature of phosphorylating agent. It is shown that the reactivity of the “activated red phosphorus” is not worse than that of the white phosphorus and significantly exceeds the reactivity of the usual technical red phosphorus.     

Controlled defect formation in elemental phosphorus as method for its chemical activation

The reveiw surveys and systematizes data on the role of defect formation in activation of red phosphorus. The reactivities of different modifications of elemental phosphorus (viz., white phosphorus, commercial red phosphorus, and red phosphorus containing high concentrations of biographical and induced defects) in inorganic and organic reactions were comparatively analyzed.     

Expedient one-pot organometallics-free synthesis of tris(2-pyridyl)phosphine from 2-bromopyridine and elemental phosphorus

2-Bromopyridine reacts with elemental phosphorus (red or white) in a superbasic KOH/DMSO(H₂O) suspension at 100 °C (for red phosphorus) and 75 °C (for white phosphorus) over 3 h to afford tris(2-pyridyl)phosphine in a 62% yield (from red phosphorus) and a 50% yield (from white phosphorus). Under microwave assistance, the reaction with red phosphorus takes just 20 min to produce tris(2-pyridyl)phosphine in 53% yield. A hitherto unknown complex, [Pd(PPy₃)₂Cl₂]·CH₂Cl₂, synthesized from tris(2-pyridyl)phosphine and PdCl₂, has the cis-configuration; this is unusual for bis(phosphino)palladium dichloride complexes.     

Mechanism of flame retardant action of red phosphorus in polyacrylonitrile

The mechanism of flame retardant (FR) action of red phosphorus in polyacrylonitrile combustion was investigated by thermogravimetry, flash-pyrolysis GC-MS, and combustion methods. Red phosphorus was found to increase the thermal stability in air of polyacrylonitrile and to induce a char residue increment on this substrate. Both these effects disappeared when pyrolysis was carried out under nitrogen flow. Flash-pyrolysis GC-MS experiments showed that red phosphorus does not alter the pyrolysis product distribution of polyacrylonitrile, which implies that there is no specific interaction between polyacrylonitrile and red phosphorus. These data also showed that polymeric red phosphorus decomposes to volatile white phosphorus (P₄) during pyrolysis. These observations allow us to propose a simple model for the mechanism of FR action of red phosphorus on polyacry-lonitrile at the molecular level. Combustion data for polyacrylonitrile-red phosphorus mixtures are in agreement with the proposed mechanism of FR action.     

Reactions of Elemental Phosphorus with Electrophiles in Super Basic Systems: XVII. Phosphorylation of Arylalkenes with Active Modifications of Elemental Phosphorus

The example of the phosphorylation of styrene and 2-vinylnaphthalene with elemental phosphorus in the KOH-DMSO system at room or elevated temperature was used to show that the activated red phosphorus prepared from white phosphorus under ionizing radiation has a reactivity comparable with that of white phosphorus and significantly higher than that of ordinary technical red phosphorus.     

Synthesis of organophosphorus compounds based on the reaction of elemental phosphorus with proton-donor reagents

Russian Journal of General Chemistry - Reaction of elemental (white) phosphorus with proton-donor reagents has been studied. The following organophosphorus compounds containing P-O and P-S bonds...     

Reactions of Elemental Phosphorus and Phosphines with Electrophiles in Superbasic Systems: XIII. Phosphorylation of Phenylacetylene with Active Modifications of Elemental Phosphorus

Phosphorylation of phenylacetylene with white or activated red phosphorus (prepared from white phosphorus under the action of ionizing radiation) occurs in KOH-DMSO or KOH-HMPA systems with heat evolution and stereoselective formation of Z isomers of tristyrylphosphine and -phosphine oxide in yields of 48-49% and 10-15%, respectively. Under the comparable conditions the commercial red phosphorus is considerably less reactive toward phenylacetylene: The total yield of the above-mentioned products is 5%.     

Structure of phosphorus clusters by simulated annealing

The combination of density functional (DF) theory with molecular dynamics (MD) allows one to simulate dynamical processes in solids, clusters and molecules without requiring a parameterization of the forces in the system. The method can also be used with the strategy of “simulated annealing” to determine structural isomers. We demonstrate the capabilities of the scheme in the case of the structure of neutral and charged phosphorus clusters, and discuss relationship between these structures and those of bulk systems (crystalline and amorphous). The results show clearly the tendency of phosphorus structures to have threefold coordination as well as “tubular” structures similar to that found in Hittorf's phosphorus (H-P). We discuss the interplay between electronic and geometric structure.     

Icosahedral and ring-shaped allotropes of phosphorus

The existence of two new allotropic forms of phosphorus, icosahedral cages and ring-shaped chains, is predicted. The cages and rings are nanostructural modifications of the black and the red phosphorus, respectively. The icosahedral and ring-shaped allotropes are compared with the experimentally known allotropic forms of phosphorus by quantum chemical methods. Both the cages and the rings are thermodynamically favored over the white phosphorus, the rings being comparable to the Hittorf's violet phosphorus and to the recently discovered fibrous red phosphorus. The stabilities of the icosahedral cages increase as a function of their size, having structural resemblance with the rhombohedral black phosphorus. The high thermodynamic stability of the phosphorus nanostructures suggests their experimental synthesis to be viable.     

Reaction of elemental phosphorus with phenols

Conclusions The composition and yield of the products formed upon the reaction of elemental phosphorus with phenols depends on the acidity of the phenol and the nature of the ring substituent. The phenol pK_a range, in which the reaction of elemental phosphorus with phenols is possible, is 9–11.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2632–2634, November, 1988.     

Encapsulation and Polymerization of White Phosphorus Inside Single-Wall Carbon Nanotubes

Elemental phosphorus displays an impressive number of allotropes with highly diverse chemical and physical properties. White phosphorus has now been filled into single-wall carbon nanotubes (SWCNTs) from the liquid and thereby stabilized against the highly exothermic reaction with atmospheric oxygen. The encapsulated tetraphosphorus molecules were visualized with transmission electron microscopy, but found to convert readily into chain structures inside the SWCNT “nanoreactors”. The energies of the possible chain structures were determined computationally, highlighting a delicate balance between the extent of polymerization and the SWCNT diameter. Experimentally, a single-stranded zig-zag chain of phosphorus atoms was observed, which is the lowest energy structure at small confinement diameters. These one-dimensional chains provide a glimpse into the very first steps of the transformation from white to red phosphorus.     

Reactions of elemental phoshorus and phosphine with electrophiles in superbasic systems: XIX. Formation of the C-P bond with participation of elemental phosphorus under microwave assistance

Microwave irradiation facilitates phosphorylation of aryl methyl chlorides and styrene with red phosphorus in the presence of strong bases and increases the yield of the main products, tertiary phosphine oxides.     

Reaction of Vinylpyridines with Active Modifications of Elemental Phosphorus in KOH/DMSO

The phosphorylation of 2-vinyl- and 4-vinylpyridines by white phosphorus and active modifications of red phosphorus (obtained by thermal polymerization of white phosphorus in the presence of graphite or the action of ionizing radiation in benzene) in the KOH/DMSO superbase system at room temperature leads to the formation of tris[2-(2-pyridyl)ethyl]- and tris[2-(4-pyridyl)ethyl]phosphine oxides in 58-72% yield. These oxides are promising ligands for design of metal complex catalysts. These vinylpyridines react less efficiently with ordinary red phosphorus and the yield of the corresponding tris(2-pyridylethyl)phosphine oxides does not exceed 10%.     

Reactions of Elemental Phosphorus and Phosphine with Electrophiles in Superbasic Media: XI.1 Phosphorylation of 4-Methoxybenzyl Chloride with Elemental Phosphorus and Phosphine

4-Methoxybenzyl chloride reacts with elemental (red or white) phosphorus under the conditions of phase-transfer catalysis (concentrated aqueous KOH, dioxane, benzyltriethylammonium chloride, 85-90°C, argon) to give as major product tris(4-methoxybenzyl)phosphine oxide in up to 45% yield. With white phosphorus at lower (70°C) temperature this reaction yields mainly bis(4-methoxybenzyl)phosphine oxide. Phosphine reacts with 4-methoxybenzyl chloride in superbasic KOH-DMSO suspension, and under definite conditions bis(4-methoxybenzyl)phosphine oxide is predominantly formed.     

Encapsulation and Polymerization of White Phosphorus Inside Single‐Wall Carbon Nanotubes

Elemental phosphorus displays an impressive number of allotropes with highly diverse chemical and physical properties. White phosphorus has now been filled into single‐wall carbon nanotubes (SWCNTs) from the liquid and thereby stabilized against the highly exothermic reaction with atmospheric oxygen. The encapsulated tetraphosphorus molecules were visualized with transmission electron microscopy, but found to convert readily into chain structures inside the SWCNT “nanoreactors”. The energies of the possible chain structures were determined computationally, highlighting a delicate balance between the extent of polymerization and the SWCNT diameter. Experimentally, a single‐stranded zig‐zag chain of phosphorus atoms was observed, which is the lowest energy structure at small confinement diameters. These one‐dimensional chains provide a glimpse into the very first steps of the transformation from white to red phosphorus.     

Cu(I) and Ru(II) complexes with elemental phosphorus as ligand: Synthesis and properties

New complexes of Cu(I) and Ru(II) with elemental (white) phosphorus (P₄), [Cu(C₅H-i-Pr₄)(η²-P₄)], [Cu(C₅H-i-Pr₄)(μ,η^2:1-P₄)Cu(C₅H-i-Pr₄)], and [Ru(C₅Me₅)(PCy₃)(η²-P₄)Cl], are synthesized with tetraphosphorus molecule as bidentate η²-ligand. The complexes are obtained by reacting elemental phosphorus with the Cu carbonyl(tetraisopropylcyclopentadienyl) complex [Cu(C₅H-i-Pr₄)(CO)] or with Ru(II) (pentamethylcyclopentadienyl)(tricyclohexylphosphine) chloride, [Ru(C₅Me₅)(PCy₃)Cl]. The structures and compositions of the obtained complexes are studied by ¹H, ³¹P NMR method and elemental analysis. The P₄ molecule is connected to Cu(I) and Ru(II) fragments through the P-P edge due to a side coordination.     

Analysis of red phosphorus in resins using pyrolysis-gas chromatography/mass spectrometry.

Although red phosphorus is used as a flame retardant for polymer materials, no analysis methods for it in resins has been established. Analysis methods for red phosphorus in resins were investigated using pyrolysis-gas chromatograpy/mass spectrometry (Py-GC/MS) by paying attention to the fact that it has a sublimation property. We found that the mass spectrum of red phosphorus shows a series of ions at m/z=62, 93 and 124, and a fragment pattern indicating that red phosphorus (P4=124, P=31) was pyrolytically decomposed. The coefficient of the correlation between the content of red phosphorus in the resin and the peak intensity in Py-GC/MS was 0.9781. The relative standard deviations of this analysis method was 6.29% (n=5). Py-GC/MS was applicable not only to qualitative analysis but also to the quantitative analysis of red phosphorus.     

Computational insight into the Rh-mediated activation of white phosphorus

Density functional calculations on the reaction of white phosphorus with the ligand bis(diphenylphosphino)methyl (dppm) at a rhodium center are presented. The cationic transition metal fragment can react as a nucleophilic as well as an electrophilic species, driven by a simple twisting of the four-membered rings. As a consequence of the conformational controlled philicity, the insertion reaction into white phosphorus occurs with a small energy barrier. The white phosphorus tetrahedron can be chelated by two cationic transition metal fragments into an opened bicyclobutane moiety, strongly stabilized by π-stacking interactions of the phenyl groups at the two transition metal fragments. It causes a 2:1 coordination; in the first stage of the reaction two molecules of the fragment add to one molecule of white phosphorus. The resulting dicationic complex easily undergoes dissociation into a cationic monoaddition product plus one cationic transition metal fragment. The ring expansion reaction of one ligand is explained by a j-step mechanism in one intermediary product. One ligand of the transition metal fragment dissociates and facilitates, by a cascade of low-energy processes, the rearrangement of the P(4)-moiety. Under bipyramid formation a PP-bond is broken, and the free ligand finally attaches to one phosphorus atom. Overall the reaction can be divided in low-energy processes, which pass through different unstable intermediates and more high-energy processes, requiring ligand dissociation.     

Microwave-assisted synthesis of cyclopentanones using the relevant phosphorus ylides

A one-pot synthesis of cyclopentanone derivatives from phosphorus ylide under lab-type microwave assisted methodology was described. The phosphorus ylides were obtained via the reaction of activated acetylenic compounds, ethyl 4-chloroacetoacetate and triphenylphosphine. The structure of phosphorus ylides was assigned by 1H, 13C and 31PNMR. The phosphorus ylides as precursor were crystallized as two enantiomers (R,R) and (S,S) and one of the phosphorus ylide structures was confirmed by single X-ray crystallography.     

Electrochemical reactions of white phosphorus

The main electrochemical transformations of elemental (white) phosphorus were considered. Special attention was given to the recently developed processes of preparation of organophosphorus compounds (OPCs) with phosphorus-carbon bonds. The electrochemical approaches to the synthesis of OPCs from white phosphorus using organonickel and organozinc reagents are described. The importance of using the electrochemical methods for the generation of highly reactive phosphorus intermediates was shown for phosphine oxide H3PO obtained for the first time. This provides significant prospects for the electrochemical approaches that could be applied for the development of technologies of the chlorine-free synthesis of OPCs from white phosphorus.