Facile synthesis of digermylene oxide and its reactivity towards vanadocene: the first example of Cp2V–germylene coordination

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3,6-Di-tert-Butyl-2-Hydroxy-4-Pyridinylphenolate and Tin(IV) Complexes it Forms: Synthesis and Structure Details and Solvatochromic Effect

Russian Journal of Coordination Chemistry - Two synthetic approaches were developed for the preparation of 3,6-di-tert-butyl-2-hydroxy-4-pyridinylphenolate (LH), a new zwitter-ionic redox-active...     

Bis-o-Semiquinonate Zinc Complexes with the Bidentate N-Donor Ligands: Synthesis and Magnetic Properties

Russian Journal of Coordination Chemistry - Biradical mononuclear SQ2 $${\text{ZnL}}_{2}^{4}$$ and SQ2ZnL5 complexes, binuclear SQ2Zn(L3)ZnSQ2 complex, and coordination polymers (SQ2ZnL1(2))n are...     

Homoligand Tris-o-Dioxolene Complexes. Peculiarities of the Molecular Structures and Magnetic Properties

Russian Journal of Coordination Chemistry - Metal tris-o-dioxolene (o-quinone, o-semiquinone, and catecholate) complexes represent an interesting and vivid model system for the demonstration of a...     

New Bis‐o‐Benzoquinoid Ligands with Ethylene Bridge and Their Metal Complexes

The treatment of di‐o‐quinone 4,4′‐(ethane‐1,2‐diyl)‐bis(3,6‐di‐tert‐butyl‐o‐benzoquinone) (Q–CH₂–CH₂–Q, 1 ) leads to its rearrangement to form di‐p‐quinomethide 4,4′‐(ethane‐1,2‐diylidene)bis(2‐hydroxy‐3,6‐di‐tert‐butyl‐cyclohexa‐2,5‐dienone) ( 2 ). The subsequent oxidation of 2 by an alkaline solution of K₃[Fe(CN)₆] yielded the new di‐o‐quinone 4,4′‐(ethene‐1,2‐diyl)bis(3,6‐di‐tert‐butyl‐o‐benzoquinone) (Q–CH=CH–Q, 3 ), which contains an ethylene bridge. The formation of mono‐ and poly‐reduced derivatives of 2 and 3 with potassium, thallium was studied by EPR technique. The dinuclear thallium derivative of 3 , Tl(SQ–CH=CH–SQ)Tl, was found to exist in the diamagnetic quinomethide form. The most stable derivatives of 2 and 3 are triphenyltin(IV) bis‐p‐quinomethide‐phenolate ( 4 ) and triphenylantimony(V) bis‐catecholate ( 5 ), which have been synthesized and isolated. The molecular structures of 2 , 3 , and 5 were characterized by single‐crystal X‐ray diffraction.     

Square-Planar Heteroleptic Complexes of α-Diimine-NiII-Catecholate Type: Intramolecular Ligand-to-Ligand Charge Transfer

Two heteroleptic Ni^II complexes combined the redox-active catecholate and 2,2′- bipyridine ligand platforms were synthesized to observe a photoinduced intramolecular ligand-to-ligand charge transfer (LL’CT, HOMO_catecholate → LUMO_α-diimine). A molecular design of compound [Ni^II(3,6-Cat)(bipy)]∙CH₃CN (1) on the base of bulky 3,6-di-tert-butyl-o-benzoquinone (3,6-DTBQ) was an annelation of the ligand with an electron donor glycol fragment, producing derivative [Ni^II(3,6-Cat^gly)(bipy)]∙CH₂Cl₂ (2), in order to influence the energy of LL’CT transition. A substantial longwave shift of the absorption peak was observed in the UV-Vis-NIR spectra of 2 compared with those in 1. In addition, the studied Ni^II derivatives demonstrated a pronounced negative solvatochromism, which was established using a broad set of solvents. The molecular geometry of both compounds can be ascribed as an insignificantly distorted square-planar type, and the π–π intermolecular stacking of the neighboring α-diimines is realized in a crystal packing. There is a lamellar crystal structure for complex 1, whereas the perpendicular T-motifs with the inter-stacks attractive π–π interactions form the packing of complex 2. The redox-active nature of ligand systems was clearly shown through the electrochemical study: a quasi-reversible one-electron reduction of 2,2′-bipyridine and two reversible successive one-electron oxidative conversations (“catecholate dianion—o-benzosemiquinonato radical anion—neutral o-benzoquinone”) were detected.     

New tin(IV) complexes with sterically hindered o‐iminobenzoquinone ligand: Synthesis and structure

The reduction of 4,6‐di‐tert‐butyl‐N‐(2, 6‐di‐iso‐propylphenyl)‐o‐iminobenzoquinone (imQ) by tin amalgam in hexane solution leads to new six‐coordinated o‐iminoquinonato tin(IV) complex (iSQ)₂SnAP ( 1 ) (where iSQ and AP are o‐iminosemiquinolate and dianion o‐amidophenolate, respectively). Variable temperature magnetic susceptibility measurements of 1 have shown that this complex possesses a weak ferromagnetic exchange between o‐iminosemiquinonate ligands. The oxidation of 1 with air oxygen produces new o‐iminoquinonolate tin(IV) derivatives [(iSQ)Sn(AP)]₂O ( 2 ) and (iSQ)₂Sn(OH)₂ ( 3 ) containing μ‐oxo‐ and hydroxo‐ligands, respectively. The electronic structure of 1 was examined by DFT analysis. Complexes 1–3 have been investigated using single‐crystal X‐ray diffraction. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:332–340, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20555     

73Ge NMR spectra in germanium single crystals with different isotopic composition

We have studied the influence of isotopic disorder on the local deformations in Ge single crystals from both experimental and calculation points of view. The nuclear magnetic resonance (NMR) spectra of⁷³Ge nuclei (the nuclear spin equals 9/2) in perfect single crystals of germanium with different isotopic content were measured at temperatures 80, 300 and 450 K. Abnormal broadening of the spectrum was found to occur when the magnetic field was aligned along the [111] axis of a crystal. The observed specific angular dependence of the quadrupole broadening was attributed to isotopic disorder among atoms of germanium sited around the⁷³Ge NMR probe. Local lattice deformations in germanium crystal lattice due to isotopic impurity atoms were calculated in the framework of the adiabatic bond charge model. The results obtained were applied to study random noncubic crystal field interactions with the nuclear quadrupole moments and corresponding effects in NMR spectra. Simulated second and fourth moments of resonance frequency distributions caused by the magnetic dipole-dipole and electric quadrupole interactions are used to analyze the lineshapes, theoretical predictions agree qualitatively with the experimental data.     

The charge exchange reaction dp → (pp)n

The ratio of the differential cross section of the charge exchange reaction of the deuteron to that of the nucleon, at small transferred momenta, has been discussed in order to estimate the spin-dependent part of the np → pn charge exchange amplitude.      

Inhomogeneous state of the electron system in the Sr14 ? x Ca x Cu24O41 superconducting cuprate: 63Cu-17O NMR study

Charge fluctuations in quasi-one-dimensional hole-doped Sr₁₄Cu₂₄O₄₁ (Ca-0) and Sr₂Ca₁₂Cu₂₄O₄₁ (Ca-12) spin-ladder cuprates have been studied with the use of ⁶³Cu-¹⁷O NMR. Spin-echo decay rates ¹⁷(1/T ₂) and ⁶³(1/T ₂) have been measured in the temperature range of T = 10–300 K. The variation of ¹⁷(1/T ₂) and ⁶³(1/T ₂) in the Ca-0 compound is monotonic in the entire temperature range of the NMR study. In the Ca-rich compound, pronounced peaks have been observed in the decay rates ¹⁷(1/T ₂) and ⁶³(1/T ₂) at temperatures of 25 and 50 K, respectively. This result indicates the presence of collective low-frequency (τ_c ∼ T ₂) charge density fluctuations in superconducting Ca-12 with an activation energy of E _A = 100(10) K. The fluctuations gradually slow down as the temperature decreases. The amplitude of the charge density fluctuations is only 0.01–0.02 hole per site. ¹⁷O-⁶³Cu spin-echo double-resonance (SEDOR) experiments in Sr_{14 − x} Ca _x Cu₂₄O₄₁ oxides with x = 0 and 12 have been performed depending on the temperature and orientation of single crystals in a magnetic field. The constants of an indirect heteronuclear ¹⁷O-⁶³Cu interaction of nuclear spins mediated by conduction electrons have been measured. The estimates of the indirect interaction constants for nearest neighbors O1-Cu and O2-Cu, as well as SEDOR experiments with selective excitation of separate sections of ¹⁷O and ⁶³Cu NMR spectra, provide convincing evidence of the microscopically inhomogeneous spatial distribution of spin density developing in a crystal. Original Russian Text ? Yu.V. Piskunov, V.V. Ogloblichev, S.V. Verkhovsky, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 11, pp. 850–855.