Neues vom P4Se4

New Results on P₄Se₄ Preparation of P₄Se₄ from the elements yields always the β-modification of P₄Se₄. α-P₄Se₄ is obtained only with selenium deficient samples. However, it is also observed, when P₄Se₃ is annealed and then extracted with CS₂. The insoluble part has the X-ray pattern of α-P₄Se₄. A reversible α-β transition is not observed. MAS-³¹P-NMR investigations on solid P₄Se₄ by Eckert et al. [2] reveal P₂Se_4/2 building units, which are, in view of our results, not dimer but linked to a polymeric network. Well-crystallized samples of β-P₄Se₄ are obtained only at measuring temperatures above 573 K. The structure is of monoclinic symmetry with the space group P2₁/n (a = 114.9, b = 729.0, c = 1211.0 pm, β = 120.80°). The reaction of α-P₄Se₃I₂ with bis-(trimethyltin)selenide in CS₂ at low temperature yields molecular α-P₄Se₄, which can be detected in solution by ³¹P-NMR spectroscopy. α-P₄Se₄ has D_2d-symmetry like α-P₄S₄. It polymerizes at higher temperature. α-P₄Se₃I(SeSnMe₃) and α-P₄Se₃(SeSnMe₃)₂ were observed in the course of this reaction, too. The analogous reaction of α-P₄Se₃I₂ with bis-(trimethyltin)sulfide leads to comparable results.     

(CuI)P4Se4: An Adduct of Polymeric P4Se4 with CuI

Pure yellow (CuI)P₄Se₄ was prepared by reaction of stoichiometric amounts of CuI, red P, and gray Se in evacuated silica ampoules. The crystal structure was determined from single crystals at room temperature. (CuI)P₄Se₄ crystallizes in the orthorhombic system, space group Cmca with a = 14.770 (1) Å, b = 12.029 (1) Å, c = 12.449 (1) Å, V = 2211.9(6) ų, and Z = 8. The structure refinement converged to R = 0.0190 (wR = 0.0272) for 1020 independent reflections and 51 parameters. A prominent feature of the crystal structure are neutral polymeric P₄Se₄ strands which are connected by copper iodide. These strands consist of norbornane analogous P₄Se₃ cages which are linked by selenium bridges. The polymers are achiral since a mirror plane exists perpendicular to the strands. The single polymers are connected by [Cu₂I₂] units to form layers. These layers are stacked along the b axis and are connected by van der Waals-interactions only. Raman spectra of (CuI)P₄Se₄ differ significantly from Raman spectra of (CuI)₃P₄Se₄ and catena-(P₄Se₄)_x.     

A New Phosphorus Selenide P4Se4

The tetraphosphorus tetraselenide P₄Se₄ is prepared and described for the first time. It is synthetised easily by heating between 250°C and 300°C a mixture of selenide P₄Se₃ and selenium. It exists under two allotropie forms, α P₄Se₄ transforming in β P₄Se₄ at 300°C. α P₄Se₄ cristallises in the orthorhombie system (a = 7.199 Å; b = 8.661 Å; c = 12.619 Å) as β P₄Se₄ (a = 9.3200 Å; b = 16.8601 Å; c = 14.3399 Å). The results of the mass spectrometry and the infra-red spectrometry suggest that the structure of the new compound derives from the tetrahedral structure of white phosphorus.     

31P solid state NMR studies of metal selenophosphates containing [P2Se6]4-, [P4Se10]4-, [PSe4]3-, [P2Se7]4-, and [P2Se9]4- ligands

31P solid-state nuclear magnetic resonance (NMR) spectra of 12 metal-containing selenophosphates have been examined to distinguish between the [P(2)Se(6)](4-), [PSe(4)](3-), [P(4)Se(10)](4-), [P(2)Se(7)](4-), and [P(2)Se(9)](4-) anions. There is a general correlation between the chemical shifts (CSs) of anions and the presence of a P[bond]P. The [P(2)Se(6)](4-) and [P(4)Se(10)](4-) anions both contain a P[bond]P and resonate between 25 and 95 ppm whereas the [PSe(4)](3-), [P(2)Se(7)](4-), and [P(2)Se(9)](4-) anions do not contain a P[bond]P and resonate between -115 and -30 ppm. The chemical shift anisotropies (CSAs) of compounds containing [PSe(4)](3-) anions are less than 80 ppm, which is significantly smaller than the CSAs of any of the other anions (range: 135-275 ppm). The smaller CSAs of the [PSe(4)](3-) anion are likely due to the unique local tetrahedral symmetry of this anion. Spin-lattice relaxation times (T(1)) have been determined for the solid compounds and vary between 20 and 3000 s. Unlike the CS, T(1) does not appear to correlate with P-P bonding. (31)P NMR is also shown to be a good method for impurity detection and identification in the solid compounds. The results of this study suggest that (31)P NMR will be a useful tool for anion identification and quantitation in high-temperature melts.     

(CuBr)3P4Se4: A Low Symmetric Variant of the (CuI)3P4Se4 Structure Type

Bright orange (CuBr)₃P₄Se₄ is obtained from the reaction of CuBr, P, and Se in stoichiometric amounts (CuBr : P : Se = 3 : 4 : 4). The composition and the crystal structure of the compound were determined from single crystal X‐ray diffraction data. Lattice constants are a = 33.627(2) Å, b = 6.402(1) Å, c = 19.059(1) Å, β = 90.19(3) °, V = 4103.2(3) ų, and Z = 12. The compound crystallizes in a structure that is related to (CuI)₃P₄Se₄. Cages of β‐P₄Se₄ are stacked along the b‐axis and are separated by columns of copper(I) bromide. However, the coordination of the β‐P₄Se₄ cage molecules to the copper atoms in the CuBr columns in (CuBr)₃P₄Se₄ is quite different from (CuI)₃P₄Se₄. The monoclinic compound (space group: P2₁, no. 4) has an almost orthorhombic metric in combination with a threefold superstructure in [100]. Structural aspects of (CuBr)₃P₄Se₄ are discussed with respect to the heavier homologue (CuI)₃P₄Se₄.     

Konzentrationen von Isomeren des Typs P m As4−m X 3 in P4S3-As4S3- und P4Se3-As4Se3-Mischungen

The reactions of P₄S₃ with As₄S₃ and of P₄Se₃ with As₄Se₃ in the molten state yields molecules of the type P _m As_4–m S₃ and P _m As_4–m Se₃, respectively. A method was developed to separate the different components by the HPLC technique, and to determine their concentrations. The identification of the isomers in the HPLC pattern was achieved with the aid of the LC-MS method. In the selenium system, the distribution of the different species is statistical. In the system P₄S₃-As₄S₃, the formation of PAs₃S₃ with one phosphorus atom in the apical position is favoured.

     

Neue Moleküle A4B3 im System P4Se3–As4Se3

Novel A₄B₃ Molecules in the System P₄Se₃–As₄Se₃ By means of ³¹P-NMR and masspectroscopic measurements in the system P₄Se₃–As₄Se₃ was shown that in the melt and vapour phase at all compositions molecules of the type P_{4 ? n}As_nSe₃ are formed. A separation was possible by liquid chromatography (RP 18-column). The concentration distribution of the different species is nearly statistical. In the solid state at ambient temperature regions of solid solubility with α-P₄Se₃, α⁺-phase, α-P₄S₃ and α-As₄Se₃ structure were observed. P₃AsSe₃ could be transformed into a plastically-crystalline phase with β-P₄S₃ structure. At higher temperatures the phase decomposes slowly. The thermal behaviour of PAs₃Se₃ is strongly influenced by the heating rate. Using low heating rates it decomposes into an amorphous phase, by fast heating a transformation into a metastable plastically-crystalline modification was achieved. During long extraction with CS₂ molecules P_{4 ? n}As_nS_{3 ? m}Se_m are formed by an exchange reaction. They can also be prepared by melting the proper amounts of the elements.     

Discrete copper(I) clusters with Cu6P6Se6 and Cu6P4Se6 cores

The reactions of chalcogenophosphinites with copper(I) metal salts are shown to yield highly stable, multi-metallic copper-chalcogen based clusters with novel topologies.     

Low valent phosphorus in the molecular anions [P5Se12]5- and beta-[P6Se12]4-: phase change behavior and near infrared second harmonic generation

The caesium salts of the novel molecular anions [P5Se12]5- and [P6Se12]4- are phase change materials and exhibit near infrared, non-linear optical second harmonic generation; [P5Se12]5- is a coordination complex with an octahedral P3+ center chelated by two [P2Se6]4- ligands whereas [P6Se12]4- features a [P2]4+ dimer chelated by two [P2Se6]4- ligands.     

P6Se12]4-: a phosphorus-rich selenophosphate with low-valent P centers

The new selenophosphate Rb4P6Se12 features the trans-decalin-like, [P6Se12]4- anion, a phosphorus-rich species that possesses three parallel P-P bonds and formally P2+ and P4+ centers. The synthesis of Rb4P6Se12 was accomplished with the reductive addition of P to RbPSe6 and represents an interesting example of how alkali chalcophosphates can serve as starting materials to produce new compounds under mild reaction conditions.     

Polynuclear Gold [AuI]4, [AuI]8, and Bimetallic [AuI4AgI] Complexes: C−H Functionalization of Carbonyl Compounds and Homogeneous Carbonylation of Amines

The synthesis of tetranuclear gold complexes, a structurally unprecedented octanuclear complex with a planar [Au^I₈] core, and pentanuclear [Au^I₄M^I] (M=Cu, Ag) complexes is presented. The linear [Au^I₄] complex undergoes C?H functionalization of carbonyl compounds under mild reaction conditions. In addition, [Au^I₄Ag^I] catalyzes the carbonylation of primary amines to form ureas under homogeneous conditions with efficiencies higher than those achieved by gold nanoparticles.     

Darstellung und Kristallstruktur des ersten polymeren Phosphorselenids catena-(P4Se4)x

Preparation and Crystal Structure of the First Polymeric Phosphorus Selenide catena-(P₄Se₄)_x Catena-(P₄Se₄)_x was prepared in crystalline form from the elements using iodine as a catalyst, and characterized by means of X-ray diffraction and IR spectroscopy. Single-crystal investigations (space group P2₁/c, a = 1 119.2(3), b = 728.2(2), c = 1 142.5(3) pm, β = 115.91(2)°, V = 837.5(7) · 10⁶ pm³) revealed parallel chains of P₄Se₃ hetero-norbornane units linked via Se atoms. Thus, being the first phosphorus selenide which does not contain discrete molecules, catena-(P₄Se₄)_x can be regarded as a polymeric form of α-P₄Se₄ or as a crystalline modification of vitrous phosphorus selenide.     

High-Resolution 77Se NMR of Ammonium Pyroselenite (NH4)2Se2O5 Crystals

The high-resolution ⁷⁷Se NMR spectra of ammonium pyroselenite crystals were recorded in the cross-polarization mode. The angular dependences of the chemical shifts of resonance lines with respect to liquid H₂SeO₄ were used to determine the chemical shift tensor parameters for the ⁷⁷Se nuclei of the Se₂O₅ pyroselenite ion.     

Chloro- und Polyselenoselenate(II) Darstellung,Struktur und Eigenschaften von [Ph3(C2H4OH)P]2[SeCl4] · MeCN, [Ph4P]2[Se2Cl6] und [Ph4P]2[Se(Se5)2]

Chloro- and Polyselenoselenates(II): Synthesis, Structure, and Properties of [Ph₃(C₂H₄OH)P]₂[SeCl₄] · MeCN, [Ph₄P]₂[Se₂Cl₆], and [Ph₄P]₂[Se(Se₅)₂] By symproportionation of elemental selenium and SeCl₄ in polar protic solvents the novel chloroselenates(+II), [SeCl₄]^2? and [Se₂Cl₆]^2?, could be stabilized; they were crystallized with voluminous organic cations. They were characterized from complete X-ray structure analysis. Yellow-orange [Ph₃(C₂H₄OH)P]₂[SeCl₄] · MeCN (space group P1 , a = 10.535(4), b = 12.204(5), c = 16.845(6) Å, α = 77.09(3)°, β = 76.40(3)°, γ = 82.75(3)° at 140 K) contains in its crystal structure monomeric [SeCl₄]^2? anions with square-planar coordination of Se(+II). The mean Se? Cl bond length is 2.441 Å. In yellow [Ph₄P]₂[Se₂Cl₆] (space group P1 , a = 10.269(3), b = 10.836(4), c = 10.872(3) Å, α = 80.26(3)°, β = 79.84(2)°, γ = 72.21(3)° at 140 K) a dinuclear centrosymmetric [Se₂Cl₆]^2? anion, also with square-planar coordinated Se(+II), is observed. The average terminal and bridging Se? Cl bond distances are 2.273 and 2.680 Å, respectively. From redox reactions of elemental Se with boranate/thiolate in ethanol/DMF the bis(pentaselenido)selenate(+II) anion [Se(Se₅)₂]^2? was prepared as a novel type of a mixed-valent chalcogenide. In dark-red-brown [Ph₄P]₂[Se(Se₅)₂] (space group P2₁/n, a = 12.748(4), b = 14.659(5), c = 14.036(5) Å, β = 108.53(3)° at 140 K) centrosymmetric molecular [Se(Se₅)₂]^2? anions with square-planar coordination of the central Se(+II) by two bidentate pentaselenide ligands is observed (mean Se? Se bond lengths: 2.658 Å at Se(+II), 2.322 Å in [Se₅]_2?). The resulting six-membered chelate rings with chair conformation are spirocyclically linked through the central Se(+II). The vibrational spectra of the new anions are reported.