Phosphorus Fragments Research Articles

The bis(Biphenyl)phosphorus Fragment in Trivalent and Tetravalent P-Environments

Diaryl substituted phosphorus (III) compounds are commonly used motifs in synthesis. Although the basic synthetic routes to these molecules starting from PCl3 are well reported, sterically hindered aryl substituents can be difficult to introduce, especially if the P atom is in ortho position to another group. This work explores the chemistry of the bis(biphenyl)phosphorus(III) fragment. As third substituents, H, M, Cl, NR2, two group 14 element substituents and also Li were introduced in high-yielding processes offering a wide chemical variety of the bis(biphenyl) phosphine motif. In addition, also a tetravalent phosphine borane adduct was isolated. All structures were thoroughly investigated by heteronuclear NMR spectroscopic analysis. Furthermore, the reaction conditions are discussed in connection with the structures and four crystal structures of the aminophosphine, phosphine, phosphine borane and phosphide are provided. The latter crystallized as a dimer with a unique planar P2Li2 ring, which is stabilized by the non-covalent C⋯Li interaction arising from the biphenyl motif and represents a rare example of a donor-free planar P2Li2 ring.

Flame-Retardant Performance of Transparent and Tensile-Strength-Enhanced Epoxy Resins.

In this study, a flame-retardant additive with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) groups denoted DSD was successfully synthesized from DOPO, 4,4′-diaminodiphenyl sulfone (DDS), and salicylaldehyde. The chemical structure of DSD was characterized by FTIR–ATR, NMR, and elemental analysis. DSD was used as an amine curing agent, and the transparent, tensile strength-enhanced epoxy resins named EP–DSD were prepared via thermal curing reactions among the diglycidyl ether of bisphenol A (DGEBA), 4,4′-diaminodiphenylmethane (DDM), and DSD. The flame-retardancy of composites was studied by the limiting oxygen index (LOI) and UL-94 test. The LOI values of EP–DSD composites increased from 30.7% for a content of 3 wt % to 35.4% for a content of 9 wt %. When the content of DSD reached 6 wt %, a V-0 rating under the UL-94 vertical test was achieved. SEM photographs of char residues after the UL-94 test indicate that an intumescent and tight char layer with a porous structure inside was formed. The TGA results revealed that EP–DSD thermosets decomposed ahead of time. The graphitization degree of the residual chars was also investigated by laser Raman spectroscopy. The measurement of tensile strength at breaking point shows that the loading of DSD increases the tensile strength of epoxy thermosets. Py-GC/MS analysis shows the presence of phosphorus fragments released during EP–DSD thermal decomposition, which could act as free radical inhibitors in the gas phase. Owing to the promotion of the formation of intumescent and compact char residues in the condensed phase and nonflammable phosphorus fragments formed from the decomposition of DOPO groups, EP–DSD composites displayed obvious flame-retardancy.

ChemInform Abstract: Beyond Triphos — New Hinges for a Classical Chelating Ligand

AbstractReview: 93 refs.

A metal-free catalyst born of frustration

Boron Catalysis Boron (a Lewis acid) and nitrogen or phosphorus fragments (both Lewis bases) tend to pair up. Keeping them separated on opposite ends of the same molecule creates a “frustrated” Lewis pair. Such molecules can manifest powerful reactivity, such as scission of the hydrogen-hydrogen

MP-BaP₃: a new phase from an old binary system.

A polyphosphide, mP-BaP3, with a unique two-dimensional phosphorus layer has been discovered and characterized. It crystallizes in the monoclinic space group P2₁/c with unit-cell parameters a=6.486(1), b=7.710(1), c=8.172(2) Å; β=104.72(3)°; Z=4. Its phosphorus polyanion can be derived from the strong elongation of 2/3 of the P-P bonds present in the layers of black phosphorus. The unit-cell volume of the mP-BaP3 phase is 1.4% larger than the volume of another polymorph, mS-BaP3, reported more than 40 years ago. The latter phase features the presence of one-dimensional phosphorus chains separated by Ba atoms. The differences in the structures of the phosphorus fragments in both polymorphs of barium triphosphide result in large differences in both the thermal stability of these materials as well as in their properties as evidenced by DSC, (31)P solid-state MAS NMR, UV/Vis, and surface photovoltage spectroscopies, alongside quantum-chemical calculations.

The 3‐Acetyloxaphosphirane/1,3,2‐Dioxaphosphol‐4‐ene Rearrangement

AbstractAn Li/Cl phosphinidenoid complex, obtained by chlorine/lithium exchange from a [dichloro(organo)phosphane]tungsten(0) complex, reacted with aliphatic dicarbonyl derivatives to provide oxaphosphirane complexes, a 1,3,2‐dioxaphosphol‐4‐ene complex, and a P‐alkoxyphosphane complex; the latter is formally derived from the enol form of the β‐diketone. DFT calculations on the ring‐expansion rearrangement support a preferred mechanism involving a pericyclic [1,3] shift of the phosphorus fragment in an oxaphosphirane complex rather than a stepwise diradical or ionic mechanism. The latter is slightly unfavored (ΔΔE‡ = 2.2 kcal/mol) and involves heterolytic P–C bond cleavage to give a methylene oxonium phosphanide intermediate and cyclization through a low‐lying transition state featuring an unusual linear C–O–P geometry.

Spin nature of genetic code

Nature has developed codon as a tool to manipulate a two-electron spin symmetry (short-living electrons, forming a radical pair, arise from the Mg-bound nucleosidetriphosphate cleavage at the triplet/singlet (T/S) crossing), which permits or forbids further nucleotide synthesis (DNA/RNA) and the synthesis of proteins. The thesis is confirmed by conducting DFT:B3LYP (6-311G** basis set) computations (T/S potential energy surfaces) with the model system composed of the template (C-G-C-G-A nucleotide sequence) and the growing chain (G-C-G nucleotide sequence, DNA or RNA). The origin of codon is in hyperfine interaction between a single electron, transferred onto the template, and three 31P nuclei built into the phosphorus fragments of nucleotides. The nuclei, together with the polynucleotide structure, form a spiral twist that is homeomorphic to a triangle patch on the Poincare sphere. Each triangle has unique angle values depending on the nucleotide nature and their position in the codon. The patch tracing produces the Berry phase changing the electron spin orientation from “up” to “down”. The Berry phase accumulation proceeds around the (T/S) conical intersections (CIs). The CIs are a result of complementary recognition between nucleotide bases at distances exceeding the commonly accepted Watson-Crick pairing by 0.17 A. Upon changing spin symmetry, the DNA or RNA chain is allowed to elongate by attaching a newly coming nucleotide. Without complementary recognition between the bases, the chain stops its elongation. The Berry phase accumulation along the patch tracing explains the effect of Crick’s wobbling when the second nucleotide plays a primary role in recognition. The data is directly linked to creation of a quantum computing device.

Phosphorylation of p-tert-butyl(thia)calixarenes by ethylene chlorophosphite

The one-step synthesis of a macrocyclic node was performed by the interaction of thiacalix[4]arene with ethylene chlorophosphite; new cyclic derivatives of calix[n]arenes containing phosphorus fragments at the lower rim in the 1,2- (n=4) and 1,2,3-alternate (n=6) configurations were obtained.

Regioselective Synthesis and Structure of New Oligophosphorylated rctt Resorcinarenes

Regioselective phosphorylation of rctt tetranaphthyl resorcinarenes gave monofunctionalized derivatives with eight phosphamide groups immobilized on the macrocyclic matrix, as well as heterofunctionalized derivatives containing hydroxyl groups on the vertically oriented benzene rings and phosphorus fragments on the planar benzene rings. GRAPHICAL ABSTRACT

Human bone ashes found in the Dama de Elche (V–IV century B.C.) reveal its use as an ancient cinerary urn

Abstract The Dama de Elche figure is a polychromed stone life-size bust and is recognized as an emblematic piece of Iberian Art (V–IV century B.C.). The Dama de Elche possesses a small cavity in the back whose function has been object of several unconfirmed hypothesis since its discovery in 1897, due to the fact that no apparent indications of its former use could be found. This research has been centered on the analysis of the cavity and the search of data as to be able to confirm its former use. A superficial base-gypsum layer that covered the sculpture had been also detected on the surface of the cavity. Afterwards a recrystallization process took place due to temperature and relative humidity changes. By microscope techniques, several carbonaceous particles have been identified that were immersed inside the recrystallized superficial CaSO 4 .2H 2 O (gypsum) layer, not visible by visual inspection. The use of the bust as a cinerary urn has been verified with the detection of carbonaceous microparticles in which phosphorus and calcium rich fragments have been identified. The obtained Ca:P ratio indicates their bone origin. The comparison of these analyzed data with other fired remains from human bone samples found in a nearby Iberian archaeological site of the same date holds a very high similarity, which confirms its analogous origin. There are also slag and sinterized particles inside the cavitiy produced at high temperatures. These results are coherent with the cremation funerary rites of Iberian culture that included the setting, even partially, of the ashes inside an urn. The detection of strontium ions, side by side the carbonaceous particles inside the cavity, are related with the thermal process induced at the time of depositing the bone ashes, still hot, from the cremation ritual. In relation to the bust authenticity, these new found data support that the Dama de Elche is a piece of Iberian culture. No data was found to support that it might have been a XIX century forgery.

A quantum-chemical and gas phase electron diffraction study of the structure of formylphosphine and acetyldimethylphosphine

The equilibrium geometry and energy and structural changes accompanying inversion motion in the phosphorus fragment and acyl group internal rotation in the H2PCHO and Me2PCMeO molecules were calculated by the MP2(full) method using basis sets from 6–31G(d, p) to 6–311G(3df, 2p). The structure of Me2PCMeO was determined by electron diffraction using the dynamic model of acyl group internal rotation based on the quantum-chemical potential function of torsional motion. Acylphosphines have amide-type equilibrium conformations with acyl groups rotated through ∼100° from their orientation in the C=O/PX2anti- form, where X = H, Me (C1 symmetry). Considerable pyramidality of the phosphorus fragment distinguishes the equilibrium structures of acylphosphines from amides with a planar molecular frame (Cs symmetry). The rh1 geometric parameters of the Me2PCMeO molecule determined by electron diffraction closely agree with quantum-chemical estimates for the equilibrium configuration.

Porphyrins with metal, metalloid or phosphorus atoms directly bonded to the carbon periphery

Organometallic porphyrins with a metal, metalloid or phosphorus fragment directly attached to their carbon framework emerged for the first time in 1976, and these macrocycles have been intensively investigated in the past decade. The present review summarises for the first time all reported examples as well as applications of these systems.

Fragmentation patterns of new esterified and unesterified aromatic 1‐hydroxymethylene‐1, 1‐bisphosphonic acids by ESI‐MSn

1-Hydroxymethylene-1,1-bisphosphonic acids (HMBPs) are compounds that have interesting pharmacological applications. Unfortunately few studies exist on their analyses by mass spectrometry (MS). In this work, we have analyzed new aromatic HMBPs and their prodrugs with electrospray tandem mass spectrometry (ESI-MS(n)). We describe, for the first time, a complete study of fragmentation patterns, in both positive and negative-ion modes. In positive mode, the cation dissociations are mainly elimination of water and phosphorus fragments. In negative mode, losses of ROH (R==H, C(6)H(5), CH(3)OC(6)H(5)) and HPO(2) were observed. The results have revealed specific structural fingerprints for the screening of these compounds in complex biological mixtures.

Regiodirected phosphorylation of 2,2′,7,7′-tetrahydroxydinaphthylmethane

The phosphorylation of 2,2′,7,7′-tetrahydroxydinaphthylmethane was studied and the influence of molecule pre-organization on the regioselectivity of functionalization was investigated. The reactions of 2,2′,7,7′-tetrahydroxydinaphthylmethane with phosphorous amides containing 1–3 amide bonds gave oligophosphorylated derivatives differing in the number and the nature of phosphorus fragments and in the size of phosphorus rings: tetraphosphorus macrocycles containing one 24-membered and two eight-membered phosphorus rings, triphosphorus compounds containing a phosphocine ring and two acyclic phosphorus fragments, and tetraphosphorylated derivatives with four phosphorus groups in the molecule. The possibility of controlling the regioselectivity of phosphorylation by using reagents differing in the number and activity of P–N bonds was demonstrated.

Synthesis and Conformation Analysis of New Perphosphorylated Calix[4]resorcinarenes

AbstractThe octaphosphorylation of calix[4]resorcinarenes 1 by 2‐dialkylamino‐1,3,2‐diheterophosphorinanes 2 is described, and the effect of different factors on the structures of the resulting perphosphorylated products 3−5 was studied. Conformation analysis of these compounds by correlated 2D NMR spectroscopy and X‐ray diffraction analysis was performed, and it was found that compounds 3−5, like the initial resorcinarenes 1, each have the all‐cis configuration of the R groups in the methylidene bridges of the calixarene system, but different orientations of benzene rings and phosphorinane fragments with respect to one another and to the macrocycle plane. Perphosphorylated resorcinarenes 3a−c, 4a and 5a with R = alkyl exist in flattened cone conformations with the phosphorinane fragments on the same side of the macrocycle plane. The conformations of the perphosphorylated resorcinarenes 3d, 4b and 5b with R = Ph change to forms intermediate between flattened cone and 1,3‐alternate. The phosphorus fragments in these compounds are located on opposite sides of the macrocycle plane. It was shown that the oxidation and sulfurisation of phosphocalixarenes 3 proceed without any change in the spatial organisation of the macrocyclic system. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Migration Reaction of a Hypervalent Fragment: Base-Induced Migration of a Phosphorane Fragment from Iron to the Cyclopentadienyl Ring in Cp(CO)2Fe{P(OC6H4Y)(OC6H4Z)} (Y, Z = NMe, NH, O)

Iron phosphorane complexes, (Y, Z = NMe, O), react with lithium diisopropylamide (LDA) and then MeI to give showing the first example of migration of a hypervalent phosphorus fragment. The structure of one of the migration products, was determined by X-ray analysis. Spectroscopic monitoring of the migration reaction suggests that the reaction is initiated by a proton abstraction on the Cp ring by LDA, followed by migration of the phosphorane fragment to the Cp ring to give which is converted into by the treatment of alkyl halide. The reaction of containing two NH groups with LDA proceeds first with NH proton abstraction to give and then with Cp proton abstraction followed by phosphorane migration to give The addition of MeI finally led to the isolation of and

The cleavage of 1-amino-2′-nitrobenzylphosphonates in a basic medium. Formation of the 3-amino-2,1-benzisoxazole derivatives

Treatment of 1-amino-2′-nitrobenzylphosphonic acids with aqueous sodium hydroxide caused a C-P bond cleavage, with formation of 3-amino-2,1-benzisoxazole derivatives ( 3). The leaving phosphorus moiety was identified here as phosphoric acid. In the case of basic hydrolysis of corresponding esters, new cyclic phosphorus compounds (derivatives of benzoxazaphosphorin-3,1,2 P v-one-2) were obtained. The cyclic products were formed as a result of the subsequent reaction of anthranil derivatives with leaving phosphorus fragment, presumably metaphosphate. These benzoxazaphosphorins (compounds 4) were converted by means of aqueous hydrochloric acid to 3-amino-2,1-benzisoxazole derivatives.

Special Properties Imparted to the 9-Phosphabicyclo[6.1.0]nonatriene system by a P-(2,4,6-tri-t-butylphenyl) substituent; 17O NMR spectrum of a bicyclic phosphirane oxide

9-(2,4,6-Tri-t-butylphenyl)-9-phosphabicyclo[6.1.0]nona-2,4,6-triene gave an observable P-oxide with t-butyl hydroperoxide. Decomposition occurred by expulsion of the phosphorus fragment, possibly as ArPO, rather than by the expected ring expansion to a phosphonin oxide. The 17O NMR shift of 18.0 is the most upfield known for a phosphine oxide.

Mutual influence of the double bond and phosphorus atom in phospholene derivatives

On the basis of an analysis of a number of characteristics (NMR and IR spectra, dipole moments) of derivatives of 2-phospholenes and 3-phospholenes with tri- and tetracoordinated phosphorus, it was concluded that there is no p-π interaction of the unshared pair of electrons of phosphorus with the double bond of 2-phospholenes, and also that the electron-acceptor properties of the phosphorus fragment predominate regardless of the valence state of the phosphorus atom.