Positron annihilation and1H NMR study of [Zn(1-propyltetrzole)6](BF4)2 and [Fe(Methyltetrazole)6](BF4)2 complexes

The complexes [Zn(1-propyltetraole)₆](BF₄)₂ (Zn-ptz) and [Fe(methyltetrazole)₆](BF₄)₂ (Fe-mtz) were investigated by positron annihilation and solid-state NMR spectroscopy. For Zn-ptz signs of structural rearrangements were found between 70 and 145 K. For the spin-crossover complex Fe-mtz a transition affecting the high-spin stat Fe²⁺ ions at lattice site B occurs below 15 K.     

High-Resolution Metal NMR Spectroscopy of Organometallic Compounds [New Analytical Methods (30)]

Great advances have been made in the past decade in the field of NMR spectroscopy. Apart from the development of completely new areas of application, such as in solid-state chemistry, in materials science, in physiological chemistry, and in medicine, with the introduction of new pulse spectroscopic methods and the application of high magnetic field strengths important progress has also been made in the traditional field of high-resolution NMR spectroscopy. Thus, among other things, the observation of metal resonances has been facilitated and new areas of application have been opened up in inorganic and organometallic chemistry. In this review, recent detection methods for spin-1/2 and quadrupolar metal nuclei are presented and discussed. The use of metal-NMR spectroscopy with respect to problems of a typical chemical nature, mainly from the field of organometallics, is demonstrated for a number of selected metal nuclei (²⁵Mg, ²⁷Al, ⁴⁹Ti, ⁵⁷Fe, ⁵⁹Co, ⁶¹Ni, ⁹¹Zr, ¹⁰³Rh, and ¹⁹⁵Pt). Relations found empirically between chemical shifts and coordination number, oxidation number, and electronic configuration of a metal bound in a complex are emphasized. Furthermore, cases in which the chemical shifts of metal nuclei can be interpreted in terms of the energy difference of frontier orbitals are presented. This aspect leads to the establishment of a relationship between chemical reactivity and NMR parameters for a series of related compounds.     

Synthesis, Characterization and Crystal Structure of （Z）-1-[2-（Triarylstannyl）vinyl]-1-indanols and Their Arylhalostannyl Derivatives

(Z)-1-[2-(Tri-o-tolylstannyl)vinyl]-1-indanol (1) and (Z)-1-[2-(tri-p-tolylstannyl)vinyl]-l-indanol (2) were synthesized by the addition reaction of 1-ethynylindanol with tri-o-tolyltin and tri-p-tolyltin hydride. The aryl groups in compound 1 and 2 were substituted by Br2 or I2 to yield monohalide derivatives (3-6). The compounds 1-6 were characterized by elemental analysis, ^1H NMR and FT-IR spectroscopy. The crystal structures of 1, 2 and 4 have been determined by single crystal X-ray diffraction analysis. The Sn atom in 1 and 2 exhibits a tetrahedral geometry distorted towards trigonal bipyramid due to a weak intramolecular interaction between Sn and the hydroxyl O atoms [0.2839(4) nm and 0.2744(5) nm], while the Sn atom in 4 adopts a trigonal bipyramidal geometry with a significant O→Sn(1) interaction [0.2552(5) nm].     

Tri(1-cyclohepta-2,4,6-trienyl)phosphan,P(C7H7)3 und Tetra(1-cyclohepta-2,4,6-trienyl)phosphonium-tetrafluoroborat, [P(C7H7)4]BF4

Tri(1-cyclohepta-2,4,6-trienyl)phosphane, P(C₇H₇)₃, and Tetra(1-cyclohepta-2,4,6-trienyl)phosphonium Tetrafluoroborate, [P(C₇H₇)₄]BF₄ The reaction of tris(trimethylsilyl)phosphane, P(SiMe₃)₃, with tropylium bromide, C₇H₇⁺Br^?, in polar solvents such as dichloromethane or tetrahydrofuran gives P(C₇H₇)₃ ( 1 ) and [P(C₇H₇)₄]Br ( 2a ). According to the X-ray crystallographic structure determinations, all 1-cyclohepta-2,4,6-trienyl substituents are present in the boat conformation in both P(C₇H₇)₃ ( 1 ) and the phosphonium salt, [P(C₇H₇)₄]BF₄ ( 2b ). The boat-shaped C₇H₇ rings are significantly more flattened if the phosphorus occupies the axial rather than the equatorial position at the ring substituent. Addition of a chalcogen to the lone pair at the central phosphorus atom of 1 leads to the chalcogena-phosphoranes EP(C₇H₇)₃ (E = O ( 3a ), S ( 3b ), Se ( 3c )). The new 1-cyclohepta-2,4,6-trienyl-phosphorus compounds 1, 2 b and 3a–c were characterized by their ¹H, ¹³C, and ³¹P NMR spectra in C₆D₆ solution.     

Nickel and copper complexes of cyclopropyltetrazole: crystal structures of [Ni(C3tz)6](BF4)2 and [Cu(C3tz)6](BF4)2

Cyclopropyltetrazole (C₃tz) and its nickel(II) and copper(II) complexes [M(C₃tz)₆](BF₄)₂] were isolated and characterized by elemental analyses, electronic spectroscopy, molar conductances, magnetic susceptibilities and single-crystal X-ray analyses.     

Low-spin state structure of [Fe(chloroethyltetrazole)6](BF4)2 obtained from synchrotron powder diffraction data

The complex [Fe(teec)6](BF4)2 (teec = chloroethyltetrazole) shows a two-step complete spin-crossover transition in the temperature range 300-90 K. Time-resolved synchrotron powder diffraction experiments have been carried out in this temperature range, and crystal structure models have been obtained from the powder patterns by using the parallel tempering technique. Of these models, the low-spin state structure at 90 K has been refined completely with Rietveld refinement. Its structural characteristics are discussed in relation to the high-spin state model and other spin-crossover compounds. The complex shows a remarkable anisotropic unit-cell parameter contraction that is dependent on the applied cooling rate. In addition, the possible important implications for the interpretation of spin-crossover behavior in terms of structural changes are discussed.     

Hypervalent Organoselenium(II) Compounds with Organophosphorus Ligands. Crystal and Molecular Structure of [2‐(iPr2NCH2)C6H4]Se[S2PR′2] (R′ = Ph,OiPr)

Redistribution reactions between diorganodiselenides of type [2‐(R₂NCH₂)C₆H₄]₂Se₂ [R = Et, iPr] and bis(diorganophosphinothioyl disulfanes of type [R′₂P(S)S]₂ (R = Ph, OiPr) resulted in the hypervalent [2‐(R₂NCH₂)C₆H₄]SeSP(S)R′₂ [R = Et, R′ = Ph ( 1 ), OiPr ( 2 ); R = iPr, R′ = Ph ( 3 ), OiPr ( 4 )] species. All new compounds were characterized by solution multinuclear NMR spectroscopy (¹H, ¹³C, ³¹P, ⁷⁷Se) and the solid compounds 1 , 3 , and 4 also by FT‐IR spectroscopy. The crystal and molecular structures of 3 and 4 were determined by single‐crystal X‐ray diffraction. In both compounds the N(1) atom is intramolecularly coordinated to the selenium atom, resulting in T‐shaped coordination arrangements of type (C,N)SeS. The dithio organophosphorus ligands act monodentate in both complexes, which can be described as essentially monomeric species. Weak intermolecular S ··· H contacts could be considered in the crystal of 3 , thus resulting in polymeric zig‐zag chains of R and S isomers, respectively.     

Phase Transition and Thermal Decomposition of [Cd(H2O)6](BF4)2

Phase transition and thermal decomposition of [Cd(H₂O)₆](BF₄)₂ were studied by differential scanning calorimetry (DSC), differential thermal analysis (DTA) and thermogravimetry (TG) methods. The solid-solid phase transition at T _C1=324 K and the melting point atT _melt.=391 K were registered. The thermal dehydration process starts just above T _C1 and continues up to T _melt.,where [Cd(H₂O)₄](BF₄)₂ in the liquid phase is formed. Then, dehydration and decomposition take place simultaneously until CdF₂ is obtained. Final products of the thermal decomposition were identified using quadrupole mass spectrometry (QMS) and X-ray diffraction methods. This revised version was published online in August 2006 with corrections to the Cover Date.     

Alkoxo‐Verbindungen des dreiwertigen Eisen: Synthese und Charakterisierung von [Fe2(OtBu)6], [Fe2Cl2(OtBu)4], [Fe2Cl4(OtBu)2] und [N(nBu)4]2[Fe6OCl6(OMe)12]

Alkoxo Compounds of Iron(III): Syntheses and Characterization of [Fe₂(OtBu)₆], [Fe₂Cl₂(OtBu)₄], [Fe₂Cl₄(OtBu)₂] and [N(nBu)₄]₂[Fe₆OCl₆(OMe)₁₂] The reaction of iron(III)chloride in diethylether with sodium tert‐butylat yielded the homoleptic dimeric tert‐‐butoxide Fe₂(OtBu)₆ ( 1 ). The chloro‐derivatives [Fe₂Cl₂(OtBu)₄] ( 2 ), and [Fe₂Cl₄(OtBu)₂] ( 3 ) could be synthesized by ligand exchange between 1 and iron(III)chloride. Each of the molecules 1 , 2 , and 3 consists of two edge‐sharing tetrahedrons, with two tert‐butoxo‐groups as μ₂‐bridging ligands. For the synthesis of the alkoxides 1 , 2 , and 3 diethylether plays an important role. In the first step the dietherate of iron(III)chloride FeCl₃(OEt₂)₂ ( 4 ) is formed. The reaction of iron(III)chloride with tetrabutylammonium methoxide in methanol results in the formation of a tetrabutylammonium methoxo‐chloro‐oxo‐hexairon cluster [N(nBu)₄]₂[Fe₆OCl₆(OMe)₁₂] ( 5 ). Crystal structure data: 1 , triclinic, P1¯, a = 9.882(2) Å, b = 10.523(2) Å, c = 15.972(3) Å, α = 73.986(4)°, β = 88.713(4)°, γ = 87.145(4)°, V = 1594.4(5) ų, Z = 2, d_c = 1.146 gcm^—1, R₁ = 0.044; 2 , monoclinic, P2₁/n, a = 11.134(2) Å, b = 10.141(2) Å, c = 12.152(2) Å und β = 114.157(3)°, V = 1251.8(4) ų, Z = 2, d_c = 1.377 gcm^—1, R₁ = 0.0581; 3 , monoclinic, P2₁/n, a = 6.527(2) Å, b = 11.744(2) Å, c = 10.623(2), β = 96.644(3)°, V = 808.8(2) ų, Z = 2, d_c = 1.641 gcm^—1, R₁ = 0.0174; 4 , orthorhombic, Iba2, a = 23.266(5) Å, b = 9.541(2) Å, c = 12.867(3) Å, V = 2856(2) ų, Z = 8, d_c = 1.444 gcm^—1, R₁ = 0.0208; 5 , trigonal, P3₁, a = 13.945(2) Å, c = 30.011(6) Å, V = 5054(2) ų, Z = 6, d_c = 1.401 gcm^—1; R_c = 0.0494.     

Preparation of 1‐X‐2, 2‐Difluoroethenylxenon(II) Tetrafluoroborates [CF2=CXXe][BF4]

The new type of alkenylxenon(II) salts [CF₂=CXXe] [BF₄] (X = H, Cl, CF₃) was prepared by reacting the corresponding alkenyldifluoroboranes CF₂=CXBF₂ with XeF₂ in 1, 1, 1, 3, 3‐pentafluoropropane (PFP) at —60 °C. The alkenylxenon(II) salts were characterised by multinuclear NMR spectroscopy. The influence of the substituent X at C‐1 on the stability of alkenylxenon(II) salts is discussed. Additionally the preparation of the potassium alkenyltrifluoroborate salts K [CF₂=CXBF₃] and their transformation into the boranes CF₂=CXBF₂ by fluoride abstraction in PFP is reported.     

Polyfluoroorganoboron‐Oxygen Compounds. 5 Feasible Routes to Perfluoroalkyltrimethoxyborates M[CnF2n+1B(OMe)3] (n ≥ 3)

A well applicable preparative method for lithium perfluoroalkyltrimethoxyborates, Li[C_nF_2n+1B(OMe)₃] (n = 3, 4, 6), was elaborated which is based on the reaction of B(OMe)₃ with C_nF_2n+1Li generated from C_nF_2n+1H and t‐BuLi. Alternative perfluoroalkylation reactions of B(OMe)₃ with perfluoropropyllithium generated from C₃F₇I and RLi, perfluoropropylmagnesium bromide, or perfluoropropyltrimethylsilane and potassium fluoride gave less satisfactory results for M[C₃F₇B(OMe)₃]. The conversion of M[C_nF_2n+1B(OMe)₃] salts (M = Li, BrMg) into K[C_nF_2n+1B(OMe)₃] salts and basic properties of the new salts are reported.     

Investigation of Spectra（NMR,Mass）of Some Fe3S3Cluster Compounds

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Transients from a mixture of [(R(O)Sn)2C(CH3)2]2 and (RCl2Sn)2C(CH3)2 [R = (SiMe3)2CH]: an identification in situ by 1D 119Sn and 2D 1H?119Sn HMQC NMR spectroscopy and electrospray mass spectrometry

The reaction of the 2,2‐bis(organodichlorostannyl)propane [(Me₃Si)₂CH(Cl₂)Sn]₂CMe₂ (A) with the corresponding organotin oxide {[(Me₃Si)₂CH(O)Sn]₂CMe₂}₂ (B) does not provide the corresponding normally expected tetraorganodistannoxane {[(Me₃Si)₂CH(Cl)SnCMe₂Sn(Cl)CH(SiMe₃)₂]O}_n but a complex reaction mixture. One major product, namely the 2,4,6,8‐tetraorgano‐2,6‐dichloro‐1,5,9‐trioxa‐2,4,6,8‐tetrastannabicyclo[3.3.1]nonane derivative [(Me₃Si)₂CHSnCMe₂Sn(Cl)CH(SiMe₃)₂]₂O₃ (C) was identified in situ by 2D ¹H? ¹¹⁹Sn and ¹H? ¹³C heteronuclear multiple quantum coherence and heteronuclear multiple bond correlation NMR spectroscopy as well as electrospray mass spectrometry. Compound C is proposed to be in equilibrium with an ionic species C′, the cation of which has an adamantane‐type structure. Copyright © 2003 John Wiley & Sons, Ltd.     

Fe4Si2Sn7O16: Eine Kombination von FeSn6-Oktaedern mit Schichten von (Fe3Sn)O6-Oktaedern; Präparation,Eigenschaften und Kristallstruktur [1]

Fe₄Si₂Sn₇O₁₆: A Combination of FeSn₆-Octahedra with Layers of (Fe₃Sn)O₆-Octahedra; Preparation, Properties, and Crystal Structure Fe₄Si₂Sn₇O₁₆ has been prepared by a solid state reaction at 900 °C from a mixture of Fe₂O₃, SnO₂, Sn, and Si. The compound is a paramagnetic semiconductor. Results of Mössbauer and suszeptibility measurements as well as bond length-bond strength calculations lead to the possible ionic formulation Fe₄²⁺Si₂⁴⁺Sn₁²⁺Sn₁⁴⁺O₁₆^2–. The compound crystallizes in the trigonal space group P3m1 (no. 164), with one formula unit per cell. Lattice parameters obtained by powder measurements are: a = 6.8243(6) Å, c = 9.1404(6) Å, γ = 120°, V = 368.6(1) ų. The structure consists of layers of edge linked oxygen octehedra exactly centered by Sn and Fe in the ratio 1 : 3. Three plains of isolated SiO₄ tetrahedra, FeSn₆ octahedra and again SiO₄ terahedra are inserted between two such layers. The layers are stacked along [001] and linked three-dimensionally by oxygen.     

Phase transitions of polycrystalline [Fe(H2O)6](ClO4)3 and [Cr(H2O)6](ClO4)3 studied by DSC

The effects of heat treatment on soymilk protein denaturation were studied by differential scanning calorimetry (DSC) and electrophoresis. Transition behavior of soymilk was studied by DSC. Three endotherms were found in DSC heating curves; the transition observed at around 70°C is attributed to the denaturation of 7S (b-conglycinin) and the transition at around 90°C is to 11S (glycinin). The denaturation temperature increased with the increasing soymilk protein content. The change of electrophoretic patterns after heat treatments indicated that soy proteins were dissociated into subunits, some of which coalesced. When the heating temperature is below their denaturation temperature, the protein fractions cannot completely be denatured even after heat exposure for extended periods of time. This revised version was published online in August 2006 with corrections to the Cover Date.     

Structural and magnetic investigations of the mixed-valence Fe(II,III) two-dimensional layer complex, [Fe2(II) Fe2(III)(HCOO)10(C6H7N)6]n.

The structure of the complex, [Fe2(II)Fe2(III)(HCOO)10(C6H7N6)n, (1) exhibits a neutral two-dimensional layer network of alternating iron(II) and iron(III) ions, bridged equatorially by formate groups. All iron atoms are octahedrally coordinated, with iron(III) coordinating axially to one gamma-picoline and one formate group, while the iron(II) centers interact axially with two gamma-picoline groups, above and below the layer plane. The complex crystallizes in the triclinic space group P1 at all studied temperatures [at 120 K, the cell dimensions are: a = 10.228(1), b = 12.071(1), c = 12.072(1) A, alpha = 89.801(2), beta = 71.149(2), gamma = 73.371(2) degrees]. An intralayer antiferromagnetic exchange interaction of J = -2.8 cm(-1) between iron(II) and iron(III) was observed in the magnetic studies. Decreasing the temperature to close to 20 K causes a magnetic-ordering phenomenon to occur and a low-temperature phase with a long-range antiferromagnetic spin orientation appears. The magnetic phase transition was confirmed by M?ssbauer spectroscopic studies at temperatures above and below the critical temperature. Structural information of 1 from synchrotron X-ray diffraction data collected at room temperature and 16 K suggests that the antiferromagnetic ordering is caused by an enhanced pi-pi interaction between chi-picoline groups from adjacent layers.     

Rare-earth tricyanomelaminates [NH(4)]Ln[HC(6)N(9)](2)[H(2)O](7)H(2)O (Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy): structural investigation, solid-state NMR spectroscopy, and photoluminescence

The rare-earth tricyanomelaminates, [NH(4)]Ln[HC(6)N(9)](2)[H(2)O](7)xH(2)O (LnTCM; Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy), have been synthesized through ion-exchange reactions. They have been characterized by powder as well as single-crystal X-ray diffraction analysis, vibrational spectroscopy, and solid-state (1)H, (13)C, and (15)N MAS NMR spectroscopy. The X-ray powder pattern common to all nine rare-earth tricyanomelaminates LnTCM (Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy) indicates that they are isostructural. The single-crystal X-ray diffraction pattern of LnTCM is indicative of non-merohedral twinning. The crystals are triclinic and separation of the twin domains as well as refinement of the structure were successfully carried out in the space group P1 for LaTCM (LaTCM; P1, Z=2, a=7.1014(14), b=13.194(3), c=13.803(3) A, alpha=90.11(3), beta=77.85(3), gamma=87.23(3) degrees , V=1262.8(4) A(3)). In the crystal structure, each Ln(3+) is surrounded by two nitrogen atoms from two crystallographically independent tricyanomelaminate moieties and seven oxygen atoms from crystal water molecules. The positions of all of the hydrogen atoms of the ammonium ions and water molecules could not be located from difference Fourier syntheses. The presence of [NH(4)](+) ions as well as two NH groups belonging to two crystallographically independent monoprotonated tricyanomelaminate moieties has only been confirmed by subjecting LaTCM to solid-state (1)H, (13)C, and (15)N{(1)H} cross-polarization (CP) MAS NMR and advanced CP experiments such as cross-polarization combined with polarization inversion (CPPI). The (1)H 2D double-quantum single-quantum homonuclear correlation (DQ SQ) spectrum and the (15)N{(1)H} 2D CP heteronuclear-correlation (HETCOR) spectrum have revealed the hydrogen-bonded (N--HN) dimer of monoprotonated tricyanomelaminate moieties as well as H-bonding through [NH(4)](+) ions and H(2)O molecules. The structures of the other eight rare-earth tricyanomelaminates (LnTCM; Ln=Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy) have been refined from X-ray powder diffraction data by the Rietveld method. Photoluminescence studies of [NH(4)]Eu[HC(6)N(9)](2)[H(2)O](7)xH(2)O have revealed orange-red (lambda(max)=615 nm) emission due to the (5)D(0)-(7)F(2) transition, whereas [NH(4)]Tb[HC(6)N(9)](2)[H(2)O](7)xH(2)O has been found to show green emission with a maximum at 545 nm arising from the (5)D(4)-(7)F(5) transition. DTA/TG studies of [NH(4)]Ln[HC(6)N(9)](2)[H(2)O](7)xH(2)O have indicated several phase transitions associated with dehydration of the compounds above 150 degrees C and decomposition above 200 degrees C.