Die Seltenerdmetallpolyselenide Gd8Se15, Tb8Se15−x,Dy8Se15−x,Ho8Se15−x,Er8Se15−x und Y8Se15−x (0 < x ≤ 0.3) – Zunehmende Fehlordnung in ausgedünnten,planaren Selenschichten

The Rare Earth Metal Polyselenides Gd₈Se₁₅, Tb₈Se_15?x, Dy₈Se_15?x, Ho₈Se_15?x, Er₈Se_15?x, and Y₈Se_15?x – Increasing Disorder in Defective Planar Selenium Layers Single crystals of the rare earth metal polyselenides Gd₈Se₁₅, Tb₈Se_15?x, Dy₈Se_15?x, Ho₈Se_15?x, Er₈Se_15?x, and Y₈Se_15?x (0 < x ≤ 0.3) have been prepared by chemical transport reactions (1120 K→ 970 K, 14 days, I₂ as carrier) starting from pre‐annealed powders of nominal compositions between LnSe₂ and LnSe_1.9. The isostructural title compounds adopt a 3 × 4 × 2 superstructure of the ZrSSi type and can be described in space group Amm2 with lattice parameters of a = 12.161(1) Å, b = 16.212(2) Å and c = 16.631(2) Å (Gd₈Se₁₅), a = 12.094(2) Å, b = 16.123(2) Å and c = 16.550(2) Å (Tb₈Se_15?x), a = 12.036(2) Å, b = 16.060(2) Å and c = 16.475(2) Å (Dy₈Se_15?x), a = 11.993(2) Å, b = 15.999(2) Å and c = 16.471(2) Å (Ho₈Se_15?x), a = 11.908(2) Å, b = 15.921(2) Å and c = 16.428(2) Å (Er₈Se_15?x), and a = 12.045(2) Å, b = 16.072(3) Å and c = 16.626(3) Å (Y₈Se_15?x), respectively. The structure consists of puckered [LnSe] double slabs and planar Se layers alternating along [001]. The planar Se layers contain a disordered arrangement of dimers, Se^2? and vacancies. All compounds are semiconducting and contain trivalent rare earth metals (Ln³⁺).     

Structure and formation of gaseous [C4H6O]+˙ ions: 1—The enolic ions [CH2C(OH)?CHCH2]+˙ and [CH2CH?CHCH(OH)]+˙ and their relationship with their keto counterparts

The [C₄H₆O]^+˙ ion of structure [CH₂?CHCH?CHOH]^+˙ (a) is generated by loss of C₄H₈ from ionized 6,6-dimethyl-2-cyclohexen-1-ol. The heat of formation ΔH_f of [CH₂?CHCH?CHOH]^+˙ was estimated to be 736 kJ mol^?1. The isomeric ion [CH₂?C(OH)CH?CH₂]^+˙ (b) was shown to have ΔH_f, ? 761 kJ mol^?1, 54 kJ mol^?1 less than that of its keto analogue [CH₃COCH?CH₂]^+˙. Ion [CH₂?C(OH)CH?CH₂]^+˙ may be generated by loss of C₂H₄ from ionized hex-1-en-3-one or by loss of C₄H₈ from ionized 4,4-dimethyl-2-cyclohexen-1-ol. The [C₄H₆O]^+˙ ion generated by loss of C₂H₄ from ionized 2-cyclohexen-1-ol was shown to consist of a mixture of the above enol ions by comparing the metastable ion and collisional activation mass spectra of [CH₂?CHCH?CHOH]^+˙ and [CH₂?C(OH)CH?CH₂]^+˙ ions with that of the above daughter ion. It is further concluded that prior to their major fragmentations by loss of CH₃˙ and CO, [CH₂?CHCH?CHOH]⁺˙ and [CH₂?C(OH)CH?CH₂]^+˙ do not rearrange to their keto counterparts. The metastable ion and collisional activation characteristics of the isomeric allenic [C₄H₆O]^+˙ ion [CH₂?C?CHCH₂OH]^+˙ are also reported.     

The potential energy surface for the [C2H2O]+˙ system: The ketene radical cation [CH2CO]+˙ and its isomers

Ab initio molecular orbital calculations with large, polarization basis sets and incorporating valence electron correlation have been employed to examine the [C₂H₂O]^+˙ potential energy surface. Four [C₂H₂O]^+˙ isomers have been identified as potentially stable, observable ions. These are the experimentally well-known ketene radical cation, [CH₂?C?O]^+˙ (a), and the presently unknown ethynol radical cation, [CH₂?C? OH]^+˙ (b), the oxirene radical cation (c) and an ion resembling a complex of CO with [CH₂]^+˙, (d). The calculated energies of b, c and d relative to a are 189, 257 and 259 kJ mol^?1, respectively. Dissociation of ions a and d is found to occur without reverse activation energy.     

Chloroselenate(IV): Darstellung,Struktur und Eigenschaften von [As(C6H5)4]2Se2Cl10 und [As(C6H5)4]Se2Cl9

Chloroselenates(IV): Synthesis, Structure, and Properties of [As(C₆H₅)₄]₂Se₂Cl₁₀ and [As(C₆H₅)₄]Se₂Cl₉ The Se₂Cl₁₀^2? and Se₂Cl₉^? anions were prepared, as the first dinuclear haloselenates(IV), from the reaction of (SeCl₄)₄ with stoichiometric quantities of chloride ions in POCl₃ solutions; they were isolated as yellow crystalline As(C₆H₅)₄⁺ salts. Complete X-ray structural analyses at ?130°C of [As(C₆H₅)₄]₂Se₂Cl₁₀ ( 1 ) (space group P1 , a = 10.296(7), b = 11.271(6), c = 12.375(8) Å, = 74.17(5)°, α = 81.38(5)°, β = 67.69(4)°, V = 1276 ų) and of [As(C₆H₅)₄]Se₂Cl₉ ( 2 ) (space group P2₁/n, a = 12.397(5), b = 17.492(6), c = 14.235(4) Å, α 93.25(3)°, V = 3082 ų) show in both cases two distorted octahedral SeCl₆ groups connected through a common edge in 1 and a common face in 2 . The terminal Se? Cl bonds (average 2.317 Å in 1 , 2.223 Å in 2 ) are much shorter than the Se? Cl bridges (av. 2.661 Å in 1 , 2.652 Å in 2 ). The stereochemical activity of the Se^IV lone electron pair causes severe distortion of the central Se₂Cl₂ ring in the centrosymmetric Se₂Cl₁₀^2? ion. The vibrational spectra of the anions are reported.     

Manganese(II) Complexes with Bridging Selenidoarsenate(III) Anions [AsSe2(Se2)]3− and [(AsSe2)2(μ‐Se2)]4−

Solvothermal reaction of [MnCl₂(terpy)] with elemental As and Se at a 1:1:2 molar ratio in H₂O/trien (10:1) at 150 °C affords the linear trimanganese(II) complex [{Mn(terpy)}₃(μ‐AsSe₄)₂] ( 1 ). The tridentate [AsSe₂(Se₂)]^3? anions of 1 chelate the terminal {Mn(terpy)}²⁺ fragments and bridge these through their remaining Se atom to the central {Mn(terpy)}²⁺ moiety. Weak interactions of Mn1···Se and Mn3···Se bonds with length 2.914(7) and 3.000(7) Å link the molecules of 1 into infinite chains. Treatment of [MnCl₂(cyclam)]Cl with As and Se at a 1:1:2 molar ratio in superheated H₂O/CH₃OH (1:1) at 150 °C yields the dinuclear complex [{Mn(cyclam)}₂ (μ‐As₂Se₆)] ( 2 ), whose novel [(AsSe₂)₂(μ‐Se₂)]^4? ligands bridge the Mn^II atoms in a μ‐1κ²Se¹, Se²: 2κ²Se⁵,Se⁶ manner.     

Mass spectrometric monitoring of oxidation of aliphatic C6–C8 hydrocarbons and ethanol in low pressure oxygen and air plasmas

Experimental and theoretical studies on the oxidation of saturated hydrocarbons (n‐hexane, cyclohexane, n‐heptane, n‐octane and isooctane) and ethanol in 28 Torr O₂ or air plasma generated by a hollow cathode discharge ion source were made. Ions corresponding to [M + 15]⁺ and [M + 13]⁺ in addition to [M ? H]⁺ and [M ? 3H]⁺ were detected as major ions where M is the sample molecule. The ions [M + 15]⁺ and [M + 13]⁺ were assigned as oxidation products, [M ? H + O]⁺ and [M ? 3H + O]⁺, respectively. By the tandem mass spectrometry analysis of [M ? H + O]⁺ and [M ? 3H + O]⁺, H₂O, olefins (and/or cycloalkanes) and oxygen‐containing compounds were eliminated from these ions. Ozone as one of the terminal products in the O₂ plasma was postulated as the oxidizing reagent. As an example, the reactions of C₆H₁₄^+? with O₂ and of C₆H₁₃⁺ (CH₃CH₂CH⁺CH₂CH₂CH₃) with ozone were examined by density functional theory calculations. Nucleophilic interaction of ozone with C₆H₁₃⁺ leads to the formation of protonated ketone, CH₃CH₂C(=OH⁺)CH₂CH₂CH₃. In air plasma, [M ? H + O]⁺ became predominant over carbocations, [M ? H]⁺ and [M ? 3H]⁺. For ethanol, the protonated acetic acid CH₃C(OH)₂⁺ (m/z 61.03) was formed as the oxidation product. The peaks at m/z 75.04 and 75.08 are assigned as protonated ethyl formate and protonated diethyl ether, respectively, and that at m/z 89.06 as protonated ethyl acetate. Copyright © 2016 John Wiley & Sons, Ltd.     

Intrinsic Acid–Base Properties of a Hexa‐2′‐deoxynucleoside Pentaphosphate,d(ApGpGpCpCpT): Neighboring Effects and Isomeric Equilibria

The intrinsic acid‐base properties of the hexa‐2′‐deoxynucleoside pentaphosphate, d(ApGpGpCpCpT) [=(A1?G2?G3?C4?C5?T6)=(HNPP)^5?] have been determined by ¹H NMR shift experiments. The pK_a values of the individual sites of the adenosine (A), guanosine (G), cytidine (C), and thymidine (T) residues were measured in water under single‐strand conditions (i.e., 10 % D₂O, 47 °C, I=0.1 M , NaClO₄). These results quantify the release of H⁺ from the two (N7)H⁺ (G?G), the two (N3)H⁺ (C?C), and the (N1)H⁺ (A) units, as well as from the two (N1)H (G?G) and the (N3)H (T) sites. Based on measurements with 2′‐deoxynucleosides at 25 °C and 47 °C, they were transferred to pK_a values valid in water at 25 °C and I=0.1 M . Intramolecular stacks between the nucleobases A1 and G2 as well as most likely also between G2 and G3 are formed. For HNPP three pK_a clusters occur, that is those encompassing the pK_a values of 2.44, 2.97, and 3.71 of G2(N7)H⁺, G3(N7)H⁺, and A1(N1)H⁺, respectively, with overlapping buffer regions. The tautomer populations were estimated, giving for the release of a single proton from five‐fold protonated H₅(HNPP)^±, the tautomers (G2)N7, (G3)N7, and (A1)N1 with formation degrees of about 74, 22, and 4 %, respectively. Tautomer distributions reveal pathways for proton‐donating as well as for proton‐accepting reactions both being expected to be fast and to occur practically at no “cost”. The eight pK_a values for H₅(HNPP)^± are compared with data for nucleosides and nucleotides, revealing that the nucleoside residues are in part affected very differently by their neighbors. In addition, the intrinsic acidity constants for the RNA derivative r(A1?G2?G3? C4?C5?U6), where U=uridine, were calculated. Finally, the effect of metal ions on the pK_a values of nucleobase sites is briefly discussed because in this way deprotonation reactions can easily be shifted to the physiological pH range.     

Density functional theory and RRKM calculations of decompositions of the metastable E‐2,4‐pentadienal molecular ions

The potential energy profiles for the fragmentations that lead to [C₅H₅O]⁺ and [C₄H₆]^+? ions from the molecular ions [C₅H₆O]^+? of E‐2,4‐pentadienal were obtained from calculations at the UB3LYP/6‐311G + + (3df,3pd)//UB3LYP/6‐31G(d,p) level of theory. Kinetic barriers and harmonic frequencies obtained by the density functional method were then employed in Rice–Ramsperger–Kassel–Marcus calculations of individual rate coefficients for a large number of reaction steps. The pre‐equilibrium and rate‐controlling step approximations were applied to different regions of the complex potential energy surface, allowing the overall rate of decomposition to be calculated and discriminated between three rival pathways: C? H bond cleavage, decarbonylation and cyclization. These processes should have to compete for an equilibrated mixture of four conformers of the E‐2,4‐pentadienal ions. The direct dissociation, however, can only become important in the high‐energy regime. In contrast, loss of CO and cyclization are observable processes in the metastable kinetic window. The former involves a slow 1,2‐hydrogen shift from the carbonyl group that is immediately followed by the formation of an ion‐neutral complex which, in turn, decomposes rapidly to the s‐trans‐1,3‐butadiene ion [C₄H₆]^+?. The predominating metastable channel is the second one, that is, a multi‐step ring closure which starts with a rate‐limiting cis—trans isomerization. This process yields a mixture of interconverting pyran ions that dissociates to the pyrylium ions [C₅H₅O]⁺. These results can be used to rationalize the CID mass spectrum of E‐2,4‐pentadienal in a low‐energy regime. Copyright © 2010 John Wiley & Sons, Ltd.     

Loss of methyl from [H2CC(OH)?CH3]+˙ ions prepared by electron impact ionization of unstable 2-hydroxypropene

Unstable 2-hydroxpropene was prepared by retro-Diels-Alder decomposition of 5-exo-methyl-5-norbornenol at 800°C/2 × 10^?6 Torr. The ionization energy of 2-hydroxypropene was measured as 8.67±0.05 eV. Formation of [C₂H₃O]⁺ and [CH₃]⁺ ions originating from different parts of the parent ion was examined by means of ¹³C and deuterium labelling. Threshold-energy [H₂C?C(OH)? CH₃]^+˙ ions decompose to CH₃CO⁺+CH₃^˙ with appearance energy AE(CH₃CO⁺) = 11.03 ± 0.03 eV. Higher energy ions also form CH₂?C?OH⁺ + CH₃ with appearance energy AE(CH₂?C?OH⁺) = 12.2–12.3 eV. The fragmentation competes with hydrogen migration between C(1) and C(3) in the parent ion. [C₂H₃O]⁺ ions containing the original methyl group and [CH₃]⁺ ions incorporating the former methylene and the hydroxyl hydrogen atom are formed preferentially, compared with their corresponding counterparts. This behaviour is due to rate-determining isomerization [H₂C?C(OH)? CH₃]^+˙ →[CH₃COCH₃]^+˙, followed by asymmetrical fragmentation of the latter ions. Effects of internal energy and isotope substitution are discussed.     

Reactivity of TpMe2‐Supported Yttrium Alkyl Complexes toward Aromatic N‐Heterocycles: Ring‐Opening or CC Bond Formation Directed by CH Activation

Unusual chemical transformations such as three‐component combination and ring‐opening of N‐heterocycles or formation of a carbon–carbon double bond through multiple C–H activation were observed in the reactions of Tp^Me2‐supported yttrium alkyl complexes with aromatic N‐heterocycles. The scorpionate‐anchored yttrium dialkyl complex [Tp^Me2Y(CH₂Ph)₂(THF)] reacted with 1‐methylimidazole in 1:2 molar ratio to give a rare hexanuclear 24‐membered rare‐earth metallomacrocyclic compound [Tp^Me2Y(μ‐N,C‐Im)(η²‐N,C‐Im)]₆ ( 1 ; Im=1‐methylimidazolyl) through two kinds of C–H activations at the C2‐ and C5‐positions of the imidazole ring. However, [Tp^Me2Y(CH₂Ph)₂(THF)] reacted with two equivalents of 1‐methylbenzimidazole to afford a C–C coupling/ring‐opening/C–C coupling product [Tp^Me2Y{η³‐(N,N,N)‐N(CH₃)C₆H₄NHCH?C(Ph)CN(CH₃)C₆H₄NH}] ( 2 ). Further investigations indicated that [Tp^Me2Y(CH₂Ph)₂(THF)] reacted with benzothiazole in 1:1 or 1:2 molar ratio to produce a C–C coupling/ring‐opening product {(Tp^Me2)Y[μ‐η²:η¹‐SC₆H₄N(CH?CHPh)](THF)}₂ ( 3 ). Moreover, the mixed Tp^Me2/Cp yttrium monoalkyl complex [(Tp^Me2)CpYCH₂Ph(THF)] reacted with two equivalents of 1‐methylimidazole in THF at room temperature to afford a trinuclear yttrium complex [Tp^Me2CpY(μ‐N,C‐Im)]₃ ( 5 ), whereas when the above reaction was carried out at 55 °C for two days, two structurally characterized metal complexes [Tp^Me2Y(Im‐Tp^Me2)] ( 7 ; Im‐Tp^Me2=1‐methyl‐imidazolyl‐Tp^Me2) and [Cp₃Y(HIm)] ( 8 ; HIm=1‐methylimidazole) were obtained in 26 and 17 % isolated yields, respectively, accompanied by some unidentified materials. The formation of 7 reveals an uncommon example of construction of a C?C bond through multiple C–H activations.     

Dinuclear Manganese(II) Complexes with Bridging Selenidodiarsenate Anions [As2Se4]4−, [As2Se5]4− and [As2Se6]2−

Solvothermal reaction of [MnCl₂(amine)] (amine = terpy and tren) with elemental As and Se at a 1:1:2 molar ratio in H₂O/tren (10:1) affords the dimanganese(II) complexes [{Mn(terpy)}₂(μ‐As₂Se₄)] ( 1 ) and [{Mn(tren)}₂(μ‐As₂Se₅)] ( 2 ) respectively. The tetradentate [As₂Se₄]^4? bridging ligands in 1 contain a central As–As bond and exhibit approximately C_2h symmetry. Pairs of gauche sited Se atoms participate in five‐membered As₂Se₂Mn chelate rings. In contrast, two AsSe₃ pyramids share a common corner in the [As₂Se₅]^4? ligands of 2 and each coordinates an [Mn(tren)]²⁺ fragment through a single terminal Se atom. Such dinuclear complexes are linked into tetranuclear moieties through weak Se···Mn interactions of length 3.026(3) Å involving one of these terminal Se atoms. At a 1:3:6 molar ratio, solvothermal reaction of [MnCl₂(tren)] with As and Se leads to formation of a second dinuclear complex [{Mn(tren)}₂(μ‐As₂Se₆)₂] ( 3 ), which contains two bridging bidentate [As₂Se₆]^2? ligands. These are cyclic with an As₂Se₄ ring and can be regarded as being derived from [As₂Se₅]^4? anions by formation of two Se‐Se bonds to an additional Se atom.     

Density functional theory and RRKM calculations of the gas‐phase unimolecular rearrangements of methylfuran and pyran ions before fragmentations

The potential energy profiles for the mutual conversion of the isomeric molecular ions [C₅H₆O]^+? of 2‐methylfuran, 3‐methylfuran and 4H‐pyran and the fragmentations that lead to [C₅H₅O]⁺ ions were obtained from calculations at the B3LYP/6‐311G + + (3df,3pd)//B3LYP/6‐31G(d,p) level of theory. The various competing unimolecular processes were characterized by their RRKM microcanonical rate coefficients, k(E), using the sets of reactant and transition state frequencies and the kinetic barriers obtained from the density functional method. In either a high‐ or a low‐energy regime, the pyrylium ion [C₅H₅O]⁺ is generated directly from the 4H‐pyran molecular ion by a simple cleavage. In contrast, in the metastable kinetic window, the molecular ions of methylfurans irreversibly isomerize to a mixture of interconverting structures before dissociation, which includes the 2H‐ and 3H‐pyran ions. The hydrogen atoms attached to saturated carbons of the pyran rings are very stabilizing at the position 2, but they are very labile at position 3 and can be shifted to adjacent positions. Once 4H‐pyran ion has been formed, the C? H bond cleavage begins before any hydrogen shift occurs. According to our calculation, there would not be complete H scrambling preceding the dissociation of the molecular ions [C₅H₆O]^+?. On the other hand, as the internal energy of the 2‐methylfuran molecular ion increases, H^? loss can become more important. These results agree with the available experimental data. Copyright © 2009 John Wiley & Sons, Ltd.     

A photo-ionization study of organosulfur ring compounds: Thiirane,thietane and tetrahydrothiophene

The gas phase heats of formation of several organosulfur cations were determined from thiirane, thietane and tetrahydrothiophene precursor molecules by photoionization mass spectrometry. Heats of formation at 0 K and 298 K are reported for the following ions: [H₂CS]^+˙, [H₃CS]⁺, [C₂H₃S]⁺, [C₂H₄S]^+˙, [C₃H₅S]⁺, [C₃H₆S]^+˙, [C₄H₇S]⁺ and [C₄H₈S]^+˙. The [C₄H₇S]⁺ (m/z 87), [C₂H₄S]^+˙ (m/z 60), [C₂H₃S]⁺ (m/z 59), [C₄H₇]⁺ (m/z 55), [C₄H₆]^+˙ (m/z 54) and [CH₂S]^+˙ (m/z 46) ions are produced from metastable tetrahydrothiophene ions at photon energies between 10.2 and 10.7 eV. Decay rates of internal energy selected parent ions to the m/z 60, 59, 55 and 54 fragments were measured by threshold photoelectron-photoion coincidence, the results of which are compared to statistical theory (RRKM/QET) calculations. The [C₂H₄S]^+˙ ion from tetrahydrothiophene is found to have the thioacetaldehyde structure. From the measured [C₂H₄S]^+˙ onset a ΔH = 50±8 kJ mol^?1 was calculated for the thioacetaldehyde molecule.     

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.     

Bis(N,N‐diethyl‐1,1‐di­seleno­carbam­ato‐Se)­selenium, [(Se2CNEt2)2Se]

The poly­seleno title compound, bis(N,N‐diethyl­seleno­carbamoyl) tri­selenide, [(Se₂CNEt₂)₂Se] or C₁₀H₂₀N₂Se₅, is obtained from the disproportion of sodium N,N‐diethyl‐1,1‐di­seleno­carbamate. An Se atom connects two N,N‐diethyl‐1,1‐di­seleno­carbamate groups with Se—Se distances in the range 2.4500 (11)–2.8601 (12) Å     

Positive chemical ionization triple‐quadrupole mass spectrometry and ab initio computational studies of the multi‐pathway fragmentation of phthalates

We report the first positive chemical ionization (PCI) fragmentation mechanisms of phthalates using triple‐quadrupole mass spectrometry and ab initio computational studies using density functional theories (DFT). Methane PCI spectra showed abundant [M + H]⁺, together with [M + C₂H₅]⁺ and [M + C₃H₅]⁺. Fragmentation of [M + H]⁺, [M + C₂H₅]⁺ and [M + C₃H₅]⁺ involved characteristic ions at m/z 149, 177 and 189, assigned as protonated phthalic anhydride and an adduct of phthalic anhydride with C₂H₅⁺ and C₃H₅⁺, respectively. Fragmentation of these ions provided more structural information from the PCI spectra. A multi‐pathway fragmentation was proposed for these ions leading to the protonated phthalic anhydride. DFT methods were used to calculate relative free energies and to determine structures of intermediate ions for these pathways. The first step of the fragmentation of [M + C₂H₅]⁺ and [M + C₃H₅]⁺ is the elimination of [R? H] from an ester group. The second ester group undergoes either a McLafferty rearrangement route or a neutral loss elimination of ROH. DFT calculations (B3LYP, B3PW91 and BPW91) using 6‐311G(d,p) basis sets showed that McLafferty rearrangement of dibutyl, di(‐n‐octyl) and di(2‐ethyl‐n‐hexyl) phthalates is an energetically more favorable pathway than loss of an alcohol moiety. Prominent ions in these pathways were confirmed with deuterium labeled phthalates. Copyright © 2010 John Wiley & Sons, Ltd.     

Selenogermanate aus wäßriger Lösung: Darstellung und Struktur von Na4Ge2Se6 · 16 H2O

Selenogermanates from Aqueous Solution: Preparation and Structure of Na₄Ge₂Se₆ · 16 H₂O Selenogermanates(IV) are prepared from aqueous solutions by reaction of alkali selenides with GeSe₂. Na₄Ge₂Se₆ · 16 H₂O, being obtained from stoichiometric 1:1 quantities, is characterized by a complete X-ray structure analysis and by vibrational spectra. The compound is monoclinic (P2₁/c) with a = 9.894(4), b = 11.781(5), c = 12.225(6) Å, β = 92.90(4)°, Z = 2. It contains isolated Ge₂Se₆^4? anions consisting of two edge-sharing tetrahedra [Ge? Se 2.303(2)–2.419(2) Å] which are in contact to the hydrated octahedral [Na(H₂O)₆]⁺ ions through Se ? H? O bridges within an extensive hydrogen bridge system. Raman-active vibrations are observed at 306, 294, 207, 139, and 121 cm^?1. Adamantane-like Ge₄Se₁₀^4? can be prepared in a similar way as Ge₂Se₆^4? if a 1:2 molar ratio of alkali selenide to GeSe₂ is employed.     

Die Kristallstrukturen von Hexachalcogeno‐Hypodiphosphaten des Magnesiums und Zinks

Crystal Structures of Hexachalcogeno‐Hypodiphosphates of Magnesium and Zinc Five chalcogeno‐hypodiphosphates were synthesized and investigated by single crystal X‐ray methods. Mg₂P₂S₆ (C2/m; a = 6.085(1), b = 10.560(2), c = 6.835(1)Å, β = 106.97(3)°; Z = 2) crystallizes with the Fe₂P₂S₆ type structure, whereas Mg₂P₂Se₆ (a = 6.404(1), c = 20.194(4)Å) and Zn₂P₂Se₆ (a = 6.290(3), c = 19.93(2)Å) build up the Fe₂P₂Se₆ type (R3; Z = 3). The structures are characterized by closest packings of sulfur (selenium) with Mg²⁺ (Zn²⁺) ions and P₂ pairs in half the octahedra — analogous to the CdCl₂ and CdI₂ type, respectively. In Mg₂P₂S₆ half the Mg²⁺ ions can be substituted by Ag⁺ ions resulting in Ag₂MgP₂S₆ (C2/n; a = 6.364(1), b = 10.975(2), c = 13.999(3)Å, β = 108.29(3)°; Z = 4). In this compound the Ag⁺ ions are disordered and located in the octahedra originally occupied by Mg²⁺ ions. In Mg₂P₂Se₆ an analogous substitution by K⁺ ions leads to the compound K₂MgP₂Se₆ (P2₁/n; a = 6.546(1), b = 12.724(3), c = 7.599(2)Å, β = 103.02(3)°; Z = 2) with K₂FeP₂S₆ type structure. The structure is characterized by columns of alternating face‐sharing Se octahedra (centered by Mg) and trigonal antiprisms (centered by P₂ pairs) along [100]. The columns are interconnected by inserted K⁺ ions.     

Neue Kronenether‐stabilisierte Oxoniumhalogenochalkogenate: [H3O(Dibromo‐benzo‐18‐Krone‐6)]2[Se3Br10] und [H5O2(Bis‐dibromo‐dibenzo‐24‐Krone‐8]2[Se3Br8]

Novel Oxonium Halogenochalcogenates Stabilized by Crown Ethers: [H₃O(Dibromo‐benzo‐18‐crown‐6)]₂[Se₃Br₁₀] and [H₅O₂(Bis‐dibromo‐dibenzo‐24‐crown‐8]₂[Se₃Br₈] Two novel complex oxonium bromoselenates(II,IV) and –(II) are reported containing [H₃O]⁺ and [H₅O₂]⁺ cations coordinated by crown ether ligands. [H₃O(dibromo‐benzo‐18‐crown‐6)]₂[Se₃Br₁₀] ( 1 ) and [H₅O₂(bis‐dibromo‐dibenzo‐24‐crown‐8]₂[Se₃Br₈] ( 2 ) were prepared as dark red crystals from dichloromethane or acetonitrile solutions of selenium tetrabromide, the corresponding unsubstituted crown ethers, and aqueous hydrogen bromide. The products were characterized by their crystal structures and by vibrational spectra. 1 is triclinic, space group (Nr. 2) with a = 8.609(2) Å, b = 13.391(3) Å, c = 13.928(3) Å, α = 64.60(2)°, β = 76.18(2)°, γ = 87.78(2)°, V = 1404.7(5) ų, Z = 1. 2 is also triclinic, space group with a = 10.499(2) Å, b = 13.033(3) Å, c = 14.756(3) Å, α = 113.77(3)°, β = 98.17(3)°, γ = 93.55(3)°. V = 1813.2(7) ų, Z = 1. In the reaction mixture complex redox reactions take place, resulting in (partial) reduction of selenium and bromination of the crown ether molecules. In 1 the centrosymmetric trinuclear [Se₃Br₁₀]^2? consists of a central Se^IVBr₆ octahedron sharing trans edges with two square planar Se^IIBr₄ groups. The novel [Se₃Br₈]^2? in 2 is composed of three planar trans‐edge sharing Se^IIBr₄ squares in a linear arrangement. The internal structure of the oxonium‐crown ether complexes is largely determined by the steric restrictions imposed by the aromatic rings in the crown ether molecules, as compared to complexes with more flexible unsubstituted crown ether ligands.     

Structural characterization of the derivatives of bis{[2,6‐(dimethylamino)methyl]phenyl} selenide with palladium(II) and mercury(II)

The intramolecularly coordinated homoleptic diorgano selenide bis{2,6‐bis[(dimethylamino)methyl]phenyl} selenide, C₂₄H₃₈N₄Se or R₂Se, where R is 2,6‐(Me₂NCH₂)₂C₆H₃, 14 , was synthesized and its ligation reactions with Pd^II and Hg^II precursors were explored. The reaction of 14 with SO₂Cl₂ and K₂PdCl₄ resulted in the formation of the meta C—H‐activated dipalladated complex {μ‐2,2′‐bis[(dimethylamino)methyl]‐4,4′‐bis[(dimethylazaniumyl)methyl]‐3,3′‐selanediyldiphenyl‐κ⁴C¹,N²:C^1′,N^2′}bis[dichloridopalladium(II)], [Pd₂Cl₄(C₂₄H₃₈N₄Se)] or [{R(H)PdCl₂}₂Se], 15 . On the other hand, when ligand 14 was reacted with HgCl₂, the reaction afforded a dimercurated selenolate complex, {μ‐bis{2,6‐bis[(dimethylamino)methyl]benzeneselanolato‐κ⁴N²,Se:Se,N⁶}‐μ‐chlorido‐bis[chloridomercury(II)], [Hg₂(C₁₂H₁₉N₂Se)Cl₃] or RSeHg₂Cl₃, 16 , where two Hg^II ions are bridged by selenolate and chloride ligands. In palladium complex 15 , there are two molecules located on crystallographic twofold axes and within each molecule the Pd moieties are related by symmetry, but there are still two independent Pd centers. Mercury complex 16 results from the cleavage of one of the Se—C bonds to form a bifurcated SeHg₂ moiety with the formal charge on the Se atom being ?1. In addition, one of the Cl ligands bridges the two Hg atoms and there are two terminal Hg—Cl bonds. Each Hg atom is in a distorted environment which can be best described as a T‐shaped base with the bridging Cl atom in an apical position, with several angles close to 90° and with one angle much larger and closer to 180°.