Systematic Study of the Interaction Between VIV Centres and Lanthanide Ions MIII in Well Defined {VIV2MIII}{AsIIIW9O33}2 Sandwich Type Clusters: Part 1

A new type of heteropolytungstate is reported that contains in a triangular arrangement one lanthanide f element and two d transition metals in form of heteroatoms. The first example in this series is the monoclinic Na₃K₅[((VO)₂Dy(H₂O)₄K₂(H₂O)₂Na(H₂O)₂)(α-B-AsW₉O₃₃)₂] · 23H₂O (1) which was prepared from an acidified aqueous solution of Na₂WO₄ · 2H₂O, As₂O₃ and VOSO₄ · 5H₂O to which Dy³⁺ ions were added. The single crystal X-ray structure analysis shows that the anion 1a consists of two [α-B-As^IIIW₉O₃₃]⁹⁻ trilacunary Keggin type units linked by two VO²⁺, one Dy³⁺ as well as two K⁺ and one Na⁺ ion, resulting in a sandwich-type structure with idealized C _2v symmetry. The complete magnetochemical analysis shows very interesting magnetic properties, which will be considered in the full series together with the properties of the homologous compounds in due course. Dedicated to Prof. Dieter Fenske on the occasion of his 65th birthday Achim Müller, Joris van Slageren and Bernt Krebs contributed in comparable extent to the paper     

Über das Anlagerungsvermögen von Salicylaldehydiminokomplexen des Nickels und Kupfers. II

A lot of nickel and copper complexes of Schiff bases were prepared and investigated for their solubility behaviour. Amine components and aldehyde components used see ?Inhaltsübersicht?. As far as investigated, the solubility of those compounds containing 4. and 5. is poor in most solvents, but it is better in pyridine. N.N′-pentamethylene-bis(salicylideneiminato)-nickel(II) is trimeric in pyridine. The copper and nickel salts containing the bulky amines 7.,8. and 9. are oligomeric (n = 2 to n = 5) in bromoform and pyridine. The salts containing 11. are monomeric in pyridine. With Stuart models it is possible to construct dimers containing 7. and 9. as amine components having square planar configuration around the metal atom. With strongly distorted tetrahedral configuration it is possible to obtain monomers. With 17., completely insoluble high polymeric compounds were obtained, whereas with 12. oligomers are found.     

Tripodal Ligands: Design of Distorted Coordination Polyhedra in Biomimetic Metal Complexes. Crystal structures of [Zn(SCN)(ntb)](SCN) · iPrpOH and [Fe(acac)(ntb)](ClO4)2 · 2CH2Cl2 · iPrpOH,ntb = N-tris(2-benzimidazolylmethyl)amine

The tripodal ligand N-tris(2-benzimidazolylmethyl)-amine (ntb) was used for the preparation of zinc(II) and iron(III) complexes, [Zn(SCN)(ntb)](SCN) · ⁱPrpOH ( 1 ) and [Fe(acac)(ntb)](ClO₄)₂ · 2CH₂Cl₂ · ⁱPrpOH ( 2 ). 1 has a highly distorted trigonal-bipyramidal ZnN₅ coordination geometry. The donor atoms are nitrogens of one amine, three benzimidazoles and one SCN^?. A striking feature of the complex is the length of the Zn? N_amine bond of 2.539(6)Å. The octahedral N₄O₂ coordination sphere of the iron in 2 is less distorted than that of the zinc in 1 . The metal is surrounded by an amine and three benzimidazole nitrogens of the ligand and two oxygens of the bidentate acetylacetonate co-ligand. The Fe? O bond lengths differ by about 0.1 Å. As for the unusual long Zn? N bond in 1 this is a result of a trans effect. 1 crystallizes in the space group P1 with: a = 9.530(1)Å, b = 13.402(1)Å, c = 13.578(2)Å, α = 98.83(1), β = 95.19(1), γ = 101.21(1)°, Z = 2; 2 is also triclinic, space group P1 , with: a = 9.875(6)Å, b = 12.929(10)Å, c = 18.635(15)Å, α = 94.95(8)°, β = 101.01(6)°, γ = 111.09(4)°, Z = 2.     

Flavonoid glycosides and other constituents of Psorospermum androsaemifolium BAKER (Clusiaceae)

Two new flavonoid glycosides, namely 3'-(2',4'-dihydroxybenzyloxy)acanthophorin B (1b) and beta,2,3',4,4',6-hexahydroxy-alpha-(alpha-L-rhamnopyranosyl)dihydrochalcone (2) were isolated from the leaves of Psorospermum androsaemifolium together with quercetin (1), acanthophorin B (1a), alpha- (3) and beta-amyrine (3a), vismiaquinone (4), 12-hentriacontanol and hentriacontane. The structures of these secondary metabolites were established using detailed spectroscopic analysis and by comparison with published data. Compounds 1, 1a, 1b, 2, 3, 3a and 4 showed weak antifungal and antibacterial activities.     

Ni-Catalyzed Borylation of Aryl Sulfoxides

A nickel/N-heterocyclic carbene (NHC) catalytic system has been developed for the borylation of aryl sulfoxides with B₂(neop)₂ (neop=neopentyl glycolato). A wide range of aryl sulfoxides with different electronic and steric properties were converted into the corresponding arylboronic esters in good yields. The regioselective borylation of unsymmetric diaryl sulfoxides was also feasible leading to borylation of the sterically less encumbered aryl substituent. Competition experiments demonstrated that an electron-deficient aryl moiety reacts preferentially. The origin of the selectivity in the Ni-catalyzed borylation of electronically biased unsymmetrical diaryl sulfoxide lies in the oxidative addition step of the catalytic cycle, as oxidative addition of methoxyphenyl 4-(trifluoromethyl)phenyl sulfoxide to the Ni(0) complex occurs selectively to give the structurally characterized complex trans-[Ni(ICy)₂(4-CF₃-C₆H₄){(SO)-4-MeO-C₆H₄}] 4 . For complex 5 , the isomer trans-[Ni(ICy)₂(C₆H₅)(OSC₆H₅)] 5 - I was structurally characterized in which the phenyl sulfinyl ligand is bound via the oxygen atom to nickel. In solution, the complex trans-[Ni(ICy)₂(C₆H₅)(OSC₆H₅)] 5 - I is in equilibrium with the S-bonded isomer trans-[Ni(ICy)₂(C₆H₅)(SOC₆H₅)] 5 , as shown by NMR spectroscopy. DFT calculations reveal that these isomers are separated by a mere 0.3 kJ/mol (M06/def2-TZVP-level of theory) and connected via a transition state trans-[Ni(ICy)₂(C₆H₅)(η²-{SO}-C₆H₅)], which lies only 10.8 kcal/mol above 5 .     

Mechanical spectroscopy of laser deposited polymers

Pulsed laser deposition (PLD) at 248 nm in ultra high vacuum was used to produce thin poly(methyl methacrylate) (PMMA) and poly(ethyl methacrylate) (PEMA) films. The ablation and deposition mechanisms were found to be similar in both systems. Having the same backbone, these polymers differ in the size of their polar side groups leading to changes in their dynamics. Studies of the relaxation processes were performed using mechanical torsion and bending spectroscopy by means of a double-paddle oscillator (DPO) and an in-situ plasma plume excited reed (PPXR), respectively. A strong increase of the mechanical damping was observed during annealing of the polymer films well above the glass transition temperature T _g, while in-situ X-ray measurements did not reveal any structural changes. For PEMA, the glass transition temperature T _g=335 K and the main absorption maximum appear at lower temperatures compared to PMMA (T _g=380 K), allowing one to measure the mechanical properties in a much wider range above T _g.     

[3 + 2] Cycloaddition of Diazomethane Derivatives to Perfluoro-2-phosphapropene

Perfluoro-2-phosphapropene ( 1 ) reacts with diazo compounds R(H)C=N₂ (R = H ( 2 a ), Ph ( 2 b ), CO₂Et ( 2 c ), Me₃Si ( 2 d )) at low temperatures regioselectively yielding via 1,3-H shift the novel 1,2,3-diazaphospholes 4 a – d . The mesomerically stabilized compounds 4 b and 4 c were characterized by NMR spectroscopy and single crystal X-ray diffraction studies. Using diphenyldiazomethane 5 as partner for 1 , the cycloaddition is spontaneously followed by N₂ elimination to give the crystalline phosphirane derivative 7 . The analogous reaction of 1 with 9-diazofluorene 9 unexpectedly leads to the so-far unknown 1,2-diphosphinane compound 11 . Quantum chemical calculations for the gas phase on DFT and RHF level prove that for both the perhydro- and the perfluoro-2-phosphapropene the [3 + 2]-cycloaddition is kinetically determined and that, due to high stability of the products, the thermodynamic equilibrium with the slightly more stable isomers is not accessible.