Ethylphosphinediacetic acid: synthesis,characterization and coordinating behaviour towards Ca(II), Ni(II) and Hg(II) ions in solution

The new ligand, ethylphosphinediacetic acid, H₂Z, was synthesized and characterized by spectral methods. The Z^2? anion is protonated in three steps with the pK values of 6.10 (phosphorus atom), 2.75 and 0.9 (carboxyl groups). The ligand is highly selective for soft metal ions as demonstrated by the stability constants of the water-soluble complexes CaHZ-(logβ_CaHZ^HZ 0.73), NiZ₂^2? (log β₂ 9.06) and HgZ₄^6? (log β₄ 40.9). The di in behaviour compared to related phosphineacetic acids are mainly consequences of the high basicity of the phosphorus atom.     

Quantum-chemical calculation of NMR chemical shifts of organic molecules: III. Intramolecular coordination effects on the 31P NMR chemical shifts of phosphorylated N-vinylazoles

Theoretical and experimental studies on magnetic shielding of the phosphorus nucleus in trichloro-[2-(1H-pyrazol-1-yl)ethenyl]phosphonium hexachlorophosphate(V) and 1,1,1,1-tetrachloro-1H-1λ⁶-pyrazolo-[1,2-a][1,2,3]diazaphosphol-8-ium-1-ide showed that intramolecular coordination of the phosphorus atom in the chlorophosphonium group to the nitrogen atom in the pyrazole ring leads to upfield shift of the phosphorus signal (to δ_P 170 ppm) and that the contribution of the spin-orbital contribution to the ³¹P chemical shift reaches 15%. Relativistic effects and effects of the medium are determining in the theoretical calculation of ³¹P NMR chemical shifts.     

Polycarboxylic acids as network modifiers for water durability improvement of inorganic-organic hybrid tin-silico-phosphate low-melting glasses

We investigated the water durability of the inorganic-organic hybrid tin-silico-phosphate glasses Me₂SiO-SnO-P₂O₅ (Me designs the organic methyl group) doped with organic acids (salicylic acid (SA), tartaric acid (TA), citric acid (CA) and butane tetracarboxylic acid (BTCA)) containing one or more of carboxylic groups per molecule. The structure, thermal properties and durability of the final glasses obtained via a non-aqueous acid-base reaction were discussed owing to the nature and the concentration of the acid added. ²⁹Si magic angle spinning (MAS) NMR and ³¹P MAS NMR spectra, respectively, showed clearly a modification of the network in the host glass matrix of the Me₂SiO-SnO-P₂O₅ system. The polycondensation enhancement to form -P-O-Si-O-P- linkages (PSP) and the increase of the Q² unit (two bridging oxygens per phosphorus atom) over the Q³ unit (three bridging oxygens per phosphorus atom) as a function of the acid in the order SA<TA<CA<BTCA, suggest the formation of a chain-like structure which contrasts with the high cross-linkage in the Me₂SiO-SnO-P₂O₅ matrix. In addition, this structural change is accompanied by a decrease of the coefficient of thermal expansion and an increase of the water durability of the glasses with the acids containing a large number of carboxylic groups per molecule. The presence of carboxylic groups of the acid acting as network modifier may retard the movement of water molecules through the glasses due to the steric hindrance strengthening the PSP connections in a chain-like structure.     

Nucleophilic Substitution at Tetracoordinate Phosphorus. Stereochemical Course and Mechanisms of Nucleophilic Displacement Reactions at Phosphorus in Diastereomeric cis- and trans-2-Halogeno-4-methyl-1,3,2-dioxaphosphorinan-2-thiones: Experimental and DFT Studies

Geometrical cis- and trans- isomers of 2-chloro-, 2-bromo- and 2-fluoro-4-methyl-1,3,2-dioxaphosphorinan-2-thiones were obtained in a diastereoselective way by (a) sulfurization of corresponding cyclic P^III-halogenides, (b) reaction of cyclic phosphorothioic acids with phosphorus pentachloride and (c) halogen–halogen exchange at P^IV-halogenide. Their conformation and configuration at the C₄-ring carbon and phosphorus stereocentres were studied by NMR (¹H, ³¹P) methods, X-ray analysis and density functional (DFT) calculations. The stereochemistry of displacement reactions (alkaline hydrolysis, methanolysis, aminolysis) at phosphorus and its mechanism were shown to depend on the nature of halogen. Cyclic cis- and trans-isomers of chlorides and bromides react with nucleophiles (HO⁻, CH₃O⁻, Me₂NH) with inversion of configuration at phosphorus. DFT calculations provided evidence that alkaline hydrolysis of cyclic thiophosphoryl chlorides proceeds according to the S_N2-P mechanism with a single transition state according to the potential energy surface (PES) observed. The alkaline hydrolysis reaction of cis- and trans-fluorides afforded the same mixture of the corresponding cyclic thiophosphoric acids with the thermodynamically more stable major product. Similar DFT calculations revealed that substitution at phosphorus in fluorides proceeds stepwise according to the A–E mechanism with formation of a pentacoordinate intermediate since a PES with two transition states was observed.     

Study of the electric dipole moments of the (C2H5)n PX3−n and P{EIVB (CH3)3}3 compounds (X = Cl,Br, I; EIVB = C,Si, Sn; n = 0, 1, 2, 3)

The dipole moments of the (C₂H₅)_nPX_3?n (X = Cl, Br, I; n = 0, 1, 2, 3) and P{E^IVB(CH₃)₃}₃ compounds (E^IVB = C, Si, Sn) have been determined by dielectric measurements in benzene at 25°C by Higasi's method. The results are interpreted in terms of an additive vector model from bond moment calculations and a maximum phosphorus lone pair contribution of 1.75 D as calculated for P(C₂H₅)₃. The high dipole moment of the mixed PA₂B-type compounds in comparison with PA₃ moments is mainly ascribed to a loss of C_3v symmetry, characterized by a quite asymmetric orientation of the phosphorus lone pair with respect to the phosphorus bonding orbitals.     

Graphite-furnace atomization of phosphorus

The slopes of the ln (absorbance) vs. T^?1 dependences for platform/graphite furnace atomization of phosphorus in the presence of Ni²⁺ or La³⁺ modifiers are measured, and found to be similar to the theoretical slope calculated for isothermal atomization. It is concluded that in both cases the atomization mechanism is the same and is expressed by P_2(gas) ? 2P_(gas); P_(gas) ? P^*_(gas). The atomic absorption signal for phosphorus appears and reaches its maximum later when the atomization is carried out from the platform in the presence of modifiers. Hence atomization takes place under nearly isothermal conditions and is much more efficient, thus providing the best conditions for the determination of phosphorus. Treatment of a deteriorated graphite surface with ZrOCl₂ solution repairs any defects and improves the sensitivity of phosphorus determination.     

From neutral iminophosphoranes to multianionic phosphazenates. The coordination chemistry of imino-aza-P(V) ligands

This review deals with the chemistry and coordination behaviour of imino-aza phosphorus(V) ligands focussing on s- and p-block as well as Group 11 and 12 metal complexes. Imino phosphorus(V) ligands contain one or more terminal RNP-units, which include iminophosphoranes R₃PNR′, monoanionic diiminophosphinates [R₂P(NR′)₂]⁻, dianionic triiminophosphonates [RP(NR′)₃]²⁻ and trianionic tetraiminophosphates [P(NR′)₄]³⁻. Aza-phosphorus(V) ligands feature bridging PNP units, which include cyclic and polymeric phosphazenes [R₂PN]_n. Imino-aza- phosphorus(V) ligands containing both imino and aza functions include linear diiminodiphosphazenates [N{R₂P(NR′)₂}₂]⁻ and multianionic poly(imino) cyclophosphazeantes such as [N₄{RP(NR′)}₄]⁴⁻ and [N₃{P(NR′)₂}₃]⁶⁻. Imino-aza phosphorus(V) ligands are assembled of three basic building blocks: the cationic tetravalent phosphonium centre (P), the anionic divalent amido function (N) and the terminally arranged R-group. The overall negative charge Z of the resulting ligand system is equal to the difference between the number of P and the number of N-centres: Z=n(P)n(N). Imino-aza phosphorus(V) ligands are electron rich N-donor ligands which co-ordinate via both N(imino) and N(aza) functions and have been applied in numerous metal complexes in order to stabilise low coordination numbers, unusual oxidation states and bonding modes or serve as ligands in homogeneous catalysis. The R-group provides both steric bulk and solubility in non-polar solvents. Multianionic phosphazenates feature a polydentate ligand surface, which facilitates an extremely high metal load. PN units of iminophosphoranes and phosphazenes have acceptor properties and enhance the acidity of α-alkyl and ortho-aryl protons. Deprotonation of P-alkyl and P-aryl iminophosphoranes give ligand systems featuring C,N chelating sites, which are also discussed.     

Laser magnetic resonance spectra of the PH radical

The PH radical has been detected by laser magnetic resonance spectroscopy at 118.6 μm in the reaction products when hydrogen atoms were passed over red phosphorus. The spectra have been identified as the N = 4 → 5 rotational transition in the ground ³∑^? state and J = 4 → 5 transition in the a¹ Δ state. The hyperfine constants for the ¹Δ state are a_p = 775 MHz and a_H = 28 MHz.     

Functionalization of white phosphorus in the coordination sphere of transition metal complexes

This review highlights the stoichiometric functionalization of both white phosphorus and naked P_n fragments derived from the metal-mediated demolition of the P₄ tetrahedron. In a first section, the alkylation of P_n ligands is discussed giving specific examples such as: (i) the electrophilic alkylation of η³-P₃ or, μ,η³-P₃ ligands: (ii) the transfer of a methyl group from molybdenum to η⁵-P₅ ligands to yield a norbornadiene-like μ₃,η⁴:η¹:η¹-MeP₇ ligand; (iii) the formation of P-C or P-H bonds mediated by rhodium and iron complexes; (iv) the use of ammonium salts to transfer an alkyl to polyphosphido clusters. Different methods to functionalise white phosphorus or other P_n ligands, including the cyclization of acrolein with diphosphenes and the insertion of CO or carbenes across P-P, P-M bonds, and P-E bonds (E = S, Se), are illustrated in appropriate sections. Finally, the last part of the article, reports on the astounding coupling of alkynes and phosphalkynes with P_n ligands which is a versatile, not yet completely explored, method to form an unprecedented variety of carbon-phosphorus heterocycles.     

Bare phosphorus and binary phosphide cluster ions generated by laser ablation

Both positive and negative phosphorus cluster ions were generated from the laser ablation of a red phosphorus sample. The mass distribution of phosphorus cluster ions was found to be very sensitive to the power density of the ablation laser. The P ₇ ⁺ species exhibits the highest signal intensity in the recorded mass spectra of bare phosphorus cluster cations, as does P ₅ ^- among the anions. Their special structural stability can be attributed to their planar configuration and their aromatic character. As the phosphorus cluster size increases, the odd/even alternation of the signal intensity becomes more pronounced. For the P _n ⁺ species with n > 24, the relative abundance varies in the order of 8 and P _n ⁺ with n = 8k + 1 (k = 3–11) are more intense than their neighbors. For comparison, some binary phosphide cluster ions, including C_nP _m ^- , Si_nP _m ^- , B_nP _m ⁺ and Al_nP _m ⁺ , were produced as well. The mass distribution of binary phosphide cluster ions changes with different components. From analysis of the recorded mass spectra of the phosphide cluster ions, the larger clusters may be in a polyhedral configuration and tend to have all valence electrons paired.     

Scrambling reactions between boron and various phosphorus moieties: The B(NEt2)3/PCl3, B(NEt2)3/OPCl3 and B(NEt2)3/SPCl3 systems

A ³¹P, ¹¹B and ¹H NMR study of the scrambling reactions between tris (diethylamino) boron B[N(C₂H₅)₂]₃ and PCl₃, OPCl₃ and SPCl₃ shows that the mixed species QCl_3−n (NEt₂)_n [Q = B, P, OP or SP and n = 1 or 2] are more favoured than would be the case if a completely random mechanism was involved. In the PCl₃/B[N(C₂H₅)₂]₃ system the chlorine substituents display preferential affinity for phosphorus moieties over boron centers while the reverse situation is encountered in the two other systems involving quadruply coordinated phosphorus. The Lewis acidity of boron and the effective electronegativity of phosphorus moieties may explain these trends.     

Multi-pumping flow system for the determination of dissolved orthophosphate and dissolved organic phosphorus in wastewater samples

A multi-pumping flow system (MPFS) for the spectrophotometric determination of dissolved orthophosphate and dissolved organic phosphorus in wastewater samples is proposed. The determination of orthophosphate is based on the vanadomolybdate method. In-line ultraviolet photo-oxidation is employed to mineralise organic phosphorus to orthophosphate prior to detection. A solenoid valve allows the deviation of the flow towards the UV-lamp to carry out the determination of organic phosphorus.Calibration was found to be linear up to 20 mg P L⁻¹, with a detection limit (3s_b/S) of 0.08 mg P L⁻¹, an injection throughput of 75 injections h⁻¹ and a repeatability (R.S.D.) of 0.6% for the direct determination of orthophosphate. On the other hand, calibration graphs were linear up to 40 mg P L⁻¹, with a detection limit (3s_b/S) of 0.5 mg P L⁻¹, an injection throughput of 11 injections h⁻¹ and a repeatability (R.S.D.) inferior to 2.3% for the procedures involving UV photo-oxidation.     

Synthesis of intermediate sitting-atop complexes (i-SAT) from the reaction between free base meso-tetraarylporphyrins and phosphorus(III) chloride in solvent free media

The reaction of meso-tetraarylporphyrins (H₂tap) with phosphorus(III) chloride has been studied in the solid state. The reaction products are intermediate sitting-atop (i-SAT) complexes in which two pyrrolenine nitrogen atoms of the porphyrins act as electron donors to the phosphorus(III) atoms and two protons on the pyrrole nitrogen atoms remain. These new complexes have been characterized by (¹H, ³¹P, ¹³C) NMR, FT-IR and UV–Vis spectroscopy, elemental analysis and electrical conductometry.     

Organometallische komplexverbindungen: VIII. Einfluss von achiralen substituenten auf die optische induktion bei der metallinduzierten synthese von 3-methyl-E-4-hexen-2-on

Bis(μ-methyl-1,3-dimethyl-η³-allylnickel) which has been modified by P ligands with a chiral substituent reacts with carbon monoxide under the formation of optically active 3-methyl-E-4-hexen-2-on. The investigated P ligands (PR^★R₂) have one chiral substituent (R^★ = 1R,3R,4S-(?)-menthyl) and the other substituents have been varied by taking the same alkyl or alkoxy groups (R = Me, Et, i-Pr, OMe, OEt, O-i-Pr). It has been found that the extent and the direction of optical induction depends on the concentration of the P-ligand and the kind of the achiral substituents at phosphorus.     

Preparation and crystal structure of the Copper Silicon Polyphosphide Cu4SiP8

The new compound Cu₄SiP₈ was prepared by solid state reaction of the elemental components. It crystallizes with a new structure type, which was determined from single-crystal X-ray diffractometer data: I4₁/a, a = 1 218.6(2) pm, c = 573.2(2) pm, Z = 8, R = 0.023 for 970 structure factors and 31 variable parameters. Tetrahedral SiP₄ groups are linked via additional phosphorus atoms to a three-dimensionally infinite silicon phosphorus network, accommodating Cu₂ pairs with octahedral phosphorus coordination as is known for the closely related structure of CuP₂. Using oxidation numbers the compound may be rationalized by the formula (Cu⁺¹)₄Si⁺⁴(P⁰)₄(P^?2)₄ in agreement with the Zintl-Klemm concept.     

Lithium tetraorganodichalcogenoimidodiphosphinates. Crystal structure of [Li{(OPPh2)(SPMe2)N}·2H2O]2, a dimer formed through oxygen-bridging phosphorus ligands

Lithium tetraorganodichalcogenoimidodiphosphinates, Li[(XPR₂)(YPR′₂)N], were prepared and investigated by means of IR and multinuclear (¹H, ¹³C, ³¹P) NMR spectroscopy. The crystal and molecular structure of lithium P,P-dimethyl-P′,P′-diphenyl-P-thioimidodiphosphinate was determined by X-ray diffraction. The asymmetric unit contains two independent dimeric associations, [Li{(OPPh₂)(SPMe₂)N}·2H₂O]₂, built up through O–phosphorus ligand bridges and separated by normal van der Waals distances. This results in the formation of a perfectly planar Li₂O₂ four-membered cycle with tetrahedral coordination around each metal atom completed by two additional O-water atoms. The sulfur atoms of the monothioimidodiphosphinato groups, which are not involved in coordination to a metal center, are on opposite sides of the Li₂O₂ cycle.     

Study of 19F chemical shifts in p-fluoro- and m-fluoro-phenylphosphine,arsine and stibine substituted metal carbonyls

The ¹⁹F chemical shift parameters provide evidence that the degree of d_π—d_π inter action between a trivalent phosphorus, arsenic or antimony ligand and a metal carbonyl moiety is non-zero.     

NMR study (1H, 13C, 29Si, 31P and 199Sn) of the (C2H5)3-n P{EIVB(CH3)3}n compounds (EIVB = C,Si; Sn; n = 0, 1, 2,3)

¹H, ¹³C, ²⁹Si, ³¹P and ¹¹⁹Sn high-resolution NMR spectra of the series (C₂H₅)₃-_n P{E^IVB(CH₃)₃}_n (E^IVB = C, Si Sn; n = 0, 1, 2, 3) have been studied at 90 and 300 Mc. The observed trend of chemical shifts and coupling constants are discussed in terms of inductive effects, through-space interactions and rehybridization of the phosphorus atom. Conclusive arguments in favor of d-orbital participation in the P-E^IVB bonds were not found.     

Synthesis,molecular structure and reactions of the novel organometallic phosphine ligand, [WI2(CO) (η2-triphos) (η2-MeC2Me)]/0.75CH2Cl2{triphos=PhP(CH2CH2PPh2)2}

Reaction of [WI₂(CO)(NCMe)(η²-MeC₂Me)₂] with an equimolar quantity of triphos {triphos=PhP(CH₂CH₂PPh₂)₂} in CH₂Cl₂ at room temperature gave the triphos complex [WI₂(CO)(η²-MeC₂Me)] (1). The crystal structure of (1) shows that the triphos is attached to the tungsten via two adjacent phosphorus atoms, with the third phosphorus atom uncoordinated. Two crystallographically independent molecules are present, which are diastereoisomers. Preliminary studies of the reactions of (1) are described.     

Insertion of electrophilic phosphorus into cyclopropanes; a new synthesis of phosphatanes

Electrophilic phosphorus reagents such as [(Cl)(i-Pr₂N)P]⁺ [AlCl₄]⁻ and PhPCl₂/AlCl₃ are found to insert into monocyclic cyclopropanes to yield phosphetanes. The utility of this new method is demonstrated by synthesizing the first phosphetanes bearing phenyl substituents at carbon.