Hexamminmetall(III)-hexachlorochromate(III): Darstellung,Kristallgitter und Spektren

Hexammine-metal(III) hexachlorochromates(III). Preparation, crystal lattic and spectra The preparation of [Me(NH₃)₆]CrCl₆ with Me = Co and Rh from aqueous solutions and with Me = Co, Cr and Rh by thermal dehydratation is given. The crystal structure of these compounds is T_h⁶? Pa3, Z = 4. The absorption spectrum shows the two known spin allowed bands at 13300 and 1890C cm^?1. Some weak vibronic absorptions are observed from 13870 cm^?1 to 15130 cm^?1. The vibrational spectrum of CrCl₆^2? has been completed by the measurement of the RAMAN spectrum, the IR spectra have been reinvestigated. The vibrational spectra confirm the nearly undisturbed octahedral symmetry of the hexahalogenometallate anion which has previously been observed for similar compounds.     

Introducing a New d0 Sc3+ Asymmetric Ion for Functional Materials: Large Birefringence Enhancement by ScO6 in Ba3Sc2(BO3)4

Transition metal ions with d⁰ electronic states (Ti⁴⁺, Zr⁴⁺, Nb⁵⁺ and Ta⁵⁺) are widely investigated as functional materials. This work first illustrates that Sc³⁺ ion, long-time ignored, displays a second-order Jahn-Teller (SOJT) effect similar to asymmetric oxide-coordinated transition metal ions, thus providing a new ground to seek for asymmetric functional materials with enhanced performances. In Ba₃Sc₂(BO₃)₄, BO₃ groups are parallelly arranged, satisfying the ideal arrangement to produce large birefringence. Importantly, distorted octahedral ScO₆ with Sc³⁺ ion in its d⁰ electronic state enlarges birefringence unexpectedly up to 0.149 @ 550 nm, which is larger than previously reported borates containing solely BO₃, even to B₃O₆ units. Subsequently, the SOJT influence of distorted ScO₆ octahedra on birefringence is verified by a comparison between experimental data and theoretical calculations. In addition, Ba₃Sc₂(BO₃)₄ also displays a high transmittance in the range of 230 nm–3.5 μm with a UV cut-off wavelength at 198 nm and a large laser induced damage threshold (2.7 GW/cm²), comparable to α-BaB₂O₄. Above characteristics imply that the title compound may be a promising birefringent material.     

Darstellung und Charakterisierung der Pentammin-Komplexe [Os(NH3)5(NCS)]2+ und [Os(NH3)5(NCSe)]2+

Preparation and Characterization of the Pentammine Complexes [Os(NH₃)₅(NCS)]²⁺ and [Os(NH₃)₅(NCSe)]²⁺ The new pentammine complexes [Os(NH₃)₅(NCS)]²⁺ and [Os(NH₃)₅(NCSe)]²⁺ are prepared from the reaction of [Os(NH₃)₅(CF₃SO₃)](CF₃ SO₃)₂ with NH₄SCN and KSeCN, respectively, in acetone, and subsequent purification by ion exchange chromatography on carboxymethyl cellulose. Evidence of N-bonding in both cases is given by the vibrational spectra, indicating that Os³⁺ is in terms of Lewis acidity harder than Ru³⁺, Rh³⁺, and Ir³⁺. I.r. and Raman spectra are interpreted according to local C_4v symmetry around Os, and the presumed assignments are confirmed by comparison with the i.r. spectra of the perdeuterated compounds. In the electronic spectra of both complexes charge transfer bands at 412 nm (NCS) and 498 nm (NCSe) are observed, respectively. Further weak absorptions near 4500 and 5100 cm^?1, which are in correlation with electronic Raman bands, are assigned to intraconfigurational transitions within the ²T_2g (O_h) ground term, split into three Kramers doubletts by spin-orbit coupling and lowered symmetry. Electrochemical measurements demonstrate a stabilisation of +III and +II oxidation states by π-back donation to —NCS and —NCSe ligands.     

The novel arsenate Na4Co7−xAl2/3x(AsO4)6 (x = 1.37): crystal structure,charge‐distribution and bond‐valence‐sum investigations

The title compound, tetrasodium cobalt aluminium hexaarsenate, Na₄Co_7−xAl_2/3x(AsO₄)₆ (x = 1.37), is isostructural with K₄Ni₇(AsO₄)₆; however, in its crystal structure, some of the Co²⁺ ions are substituted by Al³⁺ in a fully occupied octahedral site (site symmetry 2/m) and a partially occupied tetrahedral site (site symmetry 2). A third octahedral site is fully occupied by Co²⁺ ions only. One of the two independent tetrahedral As atoms and two of its attached O atoms reside on a mirror plane, as do two of the three independent Na⁺ cations, all of which are present at half‐occupancy. The proposed structural model based on a careful investigation of the crystal data is supported by charge‐distribution (CHARDI) analysis and bond‐valence‐sum (BVS) calculations. The correlation between the X‐ray refinement and the validation results is discussed.     

Interpretation of the absorption spectra of the hexaaquo cobalt(II) and hexammine cobalt(II) ions

The absorption spectra of the complex ions [Co(H₂O)₆]²⁺ and [Co(NH₃)₆]²⁺ in solution have been studied. The spectra were analyzed after breakdown of the bands into their Gaussian components by means of the formalism of a crystal field with irregular octahedral symmetry. It has been shown that interpretation of the spectra is possible only with allowance for spin-orbital coupling and orthorhombic distortion. The results obtained differ significantly from the published data.     

The Natural Optical Activity of Tris(Ethylenediamine)Metal(II) Nitrates V. The Single Crystal Circular Dichroism Spectrum of Ni(en)3 (NO3 )2

The axial CD spectra of single crystal of Zn(en)₃(NO₃)₂ doped with 1-50% Ni(en)₃(NO₃)₂ have been observed at temperatures from ambient to 5 K. The increase in R of the ³E[³T_3g(F)] transition as the temperature decreases is consistent with the magnetic dipole allowed character of the parent octahedral transition. The electric and magnetic dipole forbidden transition to the ³T_1g(F) octahedral level gives rise to a relatively weak axial CD band with an unusual temperature dependent splitting. This structure is attributed to electric quadrupole intensity, which is allowed for transitions to both the E and ³A₂[³T_1g(F)] levels in D₃ symmetry.     

Jahn—teller distortions in copper(II) complexes as determined from ESR powder spectra

Cations Cu(ligand)²⁺₆ doped in lattices of non-cubic Zn(ligand)₆(anion)₂ are shown to have ESR powder spectra, corresponding with two types of cations, distorted octahedral and regular octahedral. Upon lowering of the temperature the number of distorted molecules increases. Despite of the non-cubic symmetry the results are essentially similar to single crystal observations and investigations on cubic lattices.     

Darstellung,Schwingungsspektren und Normalkoordinatenanalyse von Hexachlororhenat(V) sowie Kristallstruktur von [P(C6H5)4][ReCl6]

Preparation, Vibrational Spectra, and Normal Coordinate Analysis of Hexachlororhenate(V) and Crystal Structure of [P(C₆H₅)₄][ReCl₆] By oxidation of A₂[ReCl₆], A = [(n-C₄H₉)₄N]⁺, [P(C₆H₅)₄]⁺, with Cl₂ in dichloromethane/trifluoracetic acid A[ReCl₆] is formed. [P(C₆H₅)₄][ReCl₆] crystallizes with tetragonal symmetry, space group P4/n-C, a = 12.967(4), c = 7.6992(8) Å, Z = 2. The octahedral complexion [ReCl₆]^? is compressed (C_4v) with the bond lengths, axial Re? Cl1 = 2.28 and Re? Cl3 = 2.24 Å, equatorial Re? Cl2 = 2.31 Å. The infrared active antisymmetric Re? Cl stretching vibration is split into v′₃ = 346 an v″₃ = 326 cm^?1. The assignment of all IR and Raman modes is confirmed by a normal coordinate analysis. The different valence force constants, f_d(ReCl1) = 2.09, f_d(ReCl3) = 2.10, f_d(ReCl2) = 1.88 mdyn/ Å result from the distortion of the octahedron. On excitation with the Ar laser line 514.5 nm a resonance Raman spectrum is observed, showing 8 overtones of v′(A₁) = 382 cm^?1, from which the harmonic frequency ω₁ = 382.1 cm^?1, the anharmonicity constant X₁₁ = ?0.76 cm^?1, and the maximum bond dissociation energy of the [ReCl₆]^? ion to be 138 kcal/mol, are calculated. The vibrational fine structure of the intraconfigurational transitions in the near infrared has been resolved by measuring the absorption spectrum of [(n-C₄H₉)₄N][ReCl₆] at low temperature (10 K), resulting in the assignment of the following electronic origins: Γ₃(³T_1g) → Γ₄(³T_1g): 7 512, Γ₃(³T_1g) → Γ₁(³T_1g): 7 624 and Γ₃(³T_1g) → Γ₅(¹T_2g), Γ₃(¹E_g): 8 368 cm^?1.     

New thallium iodates—Synthesis, characterization, and calculations of Tl(IO3)3 and Tl4(IO3)6, [Tl3Tl(IO3)6]

Two new thallium iodates have been synthesized, Tl(IO₃)₃ and Tl₄(IO₃)₆ [Tl⁺₃Tl³⁺(IO₃)₆], and characterized by single-crystal X-ray diffraction. Both materials were synthesized as phase-pure compounds through hydrothermal techniques using Tl₂CO₃ and HIO₃ as reagents. The materials crystallize in space groups R-3 (Tl(IO₃)₃) and P-1 (Tl₄(IO₃)₆). Although lone-pairs are observed for both I⁵⁺ and Tl⁺, electronic structure calculations indicate the lone-pair on I⁵⁺ is stereo-active, whereas the lone-pair on Tl⁺ is inert.     

Synthesis,spectroscopic and crystal field studies on some azido-chromium(III)-pyridine complexes

The new complexes mer-Cr(py)₃(N₃)₃, NaCr(py)₄(N₃)₄, KCr(py)₄(N₃)₄, and RbCr(py)₃(N₃)₄ (py = pyridine) have been prepared. Infrared (4000-50 cm⁻¹) and diffuse reflectance spectra (region 300-77 K) of powdered samples have been measured and discussed on bases of the known structures of these complexes. Single crystal absorption spectra for the mer-complex were obtained in the temperature range from 300 to 10 K revealing extensive vibronic structure associated with the ²E_g(O_h) and ²T_1g(O_h) electronic origins. Crystal field calculations were used to assign the bands in the vibronic region and to obtain estimates for the crystal field and Racah parameters for this class of substances. The parameters found for the mer-complex at 10 K are 10 Dq = 17906 cm⁻¹, B = 387 cm⁻¹ and C = 3381 cm⁻¹.     

The synthesis,characterisation and crystal structure of [Pt3(PPh3)2(CNC6H3Me2)6](PF6)2; a linear trinuclear cluster of platinum

[Pt₂(PPh₃)₂(CN-xylyl)₄]²⁺ (CN-xylyl = 2,6-dimethylphenyl isocyanide) and [Pt₃(PPh₃)₂(CN-xylyl)₆]²⁺ have been synthesized by reaction of [Pt(PPh₃)₂(C₂H₄)] with either [Pt(PPh₃)₂Cl₂] and CN-xylyl or [Pt(CN-xylyl)₄]²⁺. The products have been characterised by ³¹P{¹H} and ¹⁹⁵Pt{¹H} NMR spectroscopy, and a single crystal X-ray diffraction study of the trinuclear compound has demonstrated that the skeletal atoms are linear.     

Synthesis and spectroscopic characterization of trinuclear [Ru3O(O2CCH3)6(pyrazine)3]0, + clusters

Summary [Ru₃O(O₂CCH₃)₆(pyrazine)₃]^{0, +} clusters have been synthesized and characterized based on electronic, infrared and resonance Raman spectra. Selective enhancement of the pyrazine and Ru₃O(O₂CCH₃)₆ vibrational modes has been observed in the case of the reduced cluster using excitation wavelengths close to the metal-to-pyrazine and metal-metal charge transfer band in the visible region.

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Synthese und spektroskopische Charakterisierung von dreikernigen [Ru₃O(O₂CCH₃)₆(Pyrazin)₃]^{0, +}-Clustern

Zusammenfassung Es wurden [Ru₃O(O₂CCH₃)₆(Pyrazin)₃]^{0, +}-Cluster dargestellt und mittels Elektronen-, Infrarot- und Resonanz-Raman-Spektren charakterisiert. Im Fall der reduzierten Cluster wurde bei Anregungswellenlängen nahe den Metall-Pyrazin- und Metall-Metall-Charge-Transfer-Banden im sichtbaren Bereich eine selektive Anhebung der Pyrazin- und Ru₃O(O₂CCH₃)₆-Vibrationen beobachtet.

     

Coexistence of Two Different Distorted Octahedral [MnF6]3− Sites in K3[MnF6]: Manifestation in Spectroscopy and Magnetism

As a consequence of the static Jahn-Teller effect of the ⁵E ground state of Mn^III in cubic structures with octahedral parent geometries, their octahedral coordination spheres become distorted. In the case of six fluorido ligands, [MnF₆]³⁻ anions with two longer and four shorter Mn−F bonds making elongated octahedra are usually observed. Herein, we report the synthesis of the compound K₃[MnF₆] through a high-temperature approach and its crystallization by a high-pressure/high-temperature route. The main structural motifs are two quasi-isolated, octahedron-like [MnF₆]³⁻ anions of quite different nature compared to that met in ideal octahedral Mn^III Jahn-Teller systems. Owing to the internal electric field of C_i symmetry dominated by the next-neighbour K⁺ ions acting on the Mn^III sites, both sites, the pseudo-rhombic (site 1) and the pseudo-tetragonally elongated (site 2) [MnF₆]³⁻ anions are present in K₃[MnF₆]. The compound was characterized by single-crystal and powder X-ray diffraction, and magnetometry as well as by FTIR, Raman, and ligand field spectroscopy. A theoretical interpretation of the electronic structure and molecular geometry of the two Mn sites in the lattice is given by using a vibronic coupling model with parameters adjusted from multireference ab-initio cluster calculations.     

A single crystal ESR study of Gd(bipy)2(NO3)3 in La(bipy)2(NO3)3

The single crystal ESR spectrum of Gd³⁺ doped into La(bipy)₂(NO₃)₃ has been recorded at 290 K for many orientations of the crystal axes with respect to the magnetic field. A good fit of the spin Hamiltonian parameters to the experimental data has been achieved with a more efficient algorithm than previously used in this context, a significant saving being the computation of the eigenvalues only. It has been shown that previously reported spin Hamiltonian parameters for the title compound are not sufficient to describe the spectra recorded for arbitrary orientations of the single crystal and that low symmetry Gd³⁺ complexes require all possible parameters to be included.     

Intraconfigurational absorption spectroscopy of ReCl2−6 in various A2MCl6 host crystals

Low-temperature absorption and excitation spectra for Re⁴⁺ in distorted substitutional sites in K₂SnCl₆, [N(CH₃)₄]₂SnCl₆, [N(C₂H₅)₄]₂SnCl₆, [N(C₃H₇)₄]₂SnCl₆, and K₂SnBr₆ as well as in pure K₂ReCl₆ are discussed in comparison with the absorption spectra of Re⁴⁺ in cubic K₂PtCl₆, Cs₂ZrCl₆, and (NH₄)₂SnCl₆. Our data indicate that the effects of lowered symmetry are in general small and that the spectra can be interpreted in a manner paralleling earlier studies of Re⁴⁺ in cubic environments. Effects of reduced host symmetry appear to be smaller for this Kramers' ion than was previously noted for Os⁴⁺, a d⁴ system, but about equivalent to those noted for Ir⁴⁺, a d⁵ system, in the same host crystals. Origin shifts do not vary monotonically with cation size but do parallel results seen in Ir⁴⁺. In the N(C₂H₅)⁺₄ and N(C₃H₇)⁺₄ containing host crystals a significant splitting was found that correlated to two substitutional sites with parallel vibronic patterns. Low-symmetry splitting of U′_g states tended, on the contrary, to yield two sets of vibronic side bands with different intensity patterns which is an aid to assignment of the electronic state component.     

Borate Hydrides as a New Material Class: Structure,Computational Studies,and Spectroscopic Investigations on Sr5(BO3)3H and Sr5(11BO3)3D

The unprecedented borate hydride Sr₅(BO₃)₃H and deuteride Sr₅(¹¹BO₃)₃D crystallizing in an apatite-related structure are reported. Despite the presence of hydride anions, the compound decomposes only slowly in air. Doped with Eu²⁺, it shows broad-band orange-red emission under violet excitation owing to the 4f⁶5d–4f⁷ transition of Eu²⁺. The observed ¹H NMR chemical shift is in good agreement with previously reported ¹H chemical shifts of ionic metal hydrides as well as with quantum chemical calculations and very different from ¹H chemical shifts usually found for hydroxide ions in similar materials. FTIR and Raman spectroscopy of different samples containing ¹H, ²H, ^natB, and ¹¹B combined with calculations unambiguously prove the absence of hydroxide ions and the sole incorporation of hydride ions into the borate. The orange-red emission obtained by doping with Eu²⁺ shows that the new compound class might be a promising host material for optical applications.     

Observation of a possible pure electric quadrupole transition in solid Cs2NaSmCl6

A no-phonon transition has been observed in Cs₂NaSmCl₆ at 6355 cm^?1. This transition is assigned, in octahedral symmetry, as E″_u(⁶H_{$\text{5}\text{2}$}) → E'_u(⁶F_{$\text{1}\text{2}$}) and is proposed to be of pure electric quadrupole origin. A comparison between the experimental and calculated intensity and the orientation-dependent intensity of an associated vibronic transition lend support to this assignment.     

Thermochemical and spectrophotometric study of the complex formation of nickel(II) ions with sulfur containing α,ω-aminopyridines

The complexation in aqueous solution of ligands of the type o-Py? (CH₂)_(n-1) S(CH₂)_mNH₂ (n and m: 2 or 3) with Ni^II ions has been investigated. The thermodynamic functions ΔG, ΔH, and ΔS of the complex formation have been determined at 25°C in 0.5 M KNO₃ solution by means of potentiometric and of direct calorimetric titrations. They revealed that all ligands, except o-Py? (CH₂)₂S(CH₂)₃NH₂ for which no appreciable complexation with Ni^II could be stated, act as tridentates towards Ni^II. Information on the stereochemistry of the Ni^II complexes was obtained from the electronic spectra. The NiL²⁺ and NiL₂²⁺ complexes both have distorted octahedral structures. The NiL₂²⁺ species were also compared to the corresponding NiL₂(NO₃)₂ compounds in the solid state.     

Two new phosphate langbeinites,Rb2YbTi(PO4)3 and Rb2Yb0.32Ti1.68(PO4)3, investigated at 293 and 150 K

The rubidium ytterbium titanium phosphates Rb₂YbTi(PO₄)₃, (I), and Rb₂Yb_0.32Ti_1.68(PO₄)₃, (II), have been structurally characterized from X‐ray data collected at both 293 and 150 K. Compound (II) is blue owing to the presence of mixed‐valence titanium (41% Ti³⁺ + 59% Ti⁴⁺). Both (I) and (II) belong to the langbeinite structure type, with mixed Yb/Ti populations in the two crystallographically independent octahedral sites (of symmetry 3). Ytterbium favours one of these sites, where about two‐thirds of the Yb atoms are found. The O‐atom displacement parameters are large in both compounds at both temperatures.     

Free electron model in cluster structure theory. Electronic structures of [Mo6S8(CN)6]6?, [Mo6Se8(CN)6]6?, [Re6S8(CN)6]4?, and Rh6(CO)16 clusters

The results of quantum chemical calculations of the electronic structure and geometry of octahedral clusters [Mo₆S₈(CN)₆]⁶⁻, [Mo₆Se₈(CN)₆]⁶⁻, [Re₆S₈(CN)₆]⁴⁻, and Rh₆(CO)₁₆ by the ab initio SCF (RHF) and DFT (B3LYP) methods with various basis sets are presented. The electronic states of the clusters under study in ideal spherically symmetric potential were classified in the orbital quantum number l (1s, 1p, 1d, 1f, 1g, 1h, 1i), l = 0–6. In real crystal field with O_h symmetry these states are split. The calculated new electronic states were matched to the irreducible representations of the point symmetry group O_h. The polarizabilities of the compounds considered are 55–65 ų. A new model for the electronic structure of octahedral clusters containing M₆ groups was proposed. The model is based on the idea of free electrons moving in spherically symmetric potential field. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2617–2624, December, 2005.