RAMAN-SPECTROSCOPIC STUDY OF LAYER STRUCTURE COMPOUND [N-CNH2N+1NH3]2ZNCL4

The C-H stretching, C-H bending, C-C stretching and the low-frequency vibration regions have been investigated by Raman spectroscopy for [n-CnH2n+1NH3]2 ZnCl4 with n=7 approximately 12, 16. It is found that their frequency and relative intensities are related to the length of carbon chain in the molecules and present the odd-even effect to carbon atom numbers in chain. Some changes in spectra are interpreted in terms of the different molecular packing and interaction of chain.

AN INFRARED SPECTROSCOPIC STUDY OF THE STRUCTURAL PHASE-TRANSITION IN THE PEROVSKITE-TYPE LAYER COMPOUND [N-C16H33NH3]2COCL4

The solid-solid phase transitions in the perovskite-type layer compound [n- C16H33NH3]2CoCl4 have been studied by infrared spectroscopy. A new phase transition at 340 K was found by comparison with differential scanning calorimetry results. A temperature dependence study of the infrared spectra provides evidence of the occurrence of structural phase transitions related to the dynamics of the alkylammonium ions and hydrogen bonds. The main transition at 374 K corresponds to the conformational order-disorder change in the chain, which probably couples with reorientational motions of the NH3 polar heads. GTG or GTG' defects appear in the high temperature disordered phase.

SYNTHESES AND X-RAY STRUCTURES OF BIS(T-BUTYLCYCLOPENTADIENYL)LANTHANIDE CHLORIDE COMPLEXES [(BU(T)CP)2LNCL]2 (LN = PR, GD, ER)

Reaction of lanthanide trichlorides with two equivalents of sodium t-butylcyclopentadienide in THF gave rise to the bis(t-butylcyclopentadienyl)lanthanide chloride complexes [(Bu(t)Cp)2LnCl]2 (Ln = Pr, Gd, Er), which were characterized by elemental analysis, IR and H-1 NMR spectroscopy. In addition, the crystal structures of [(ButCp)2PrCl]2 (1) and [(ButCp)2GdCl]2 (2) were determined by single crystal X-ray diffraction at room temperature. The coordination number for Pr3+ and Gd3+ is 8 and the bond lengths Pr-Cl and Gd-Cl are 2.864(2) and 2.771(3) angstrom, respectively. The structural studies showed the complexes to have C2h symmetry.

DIELS-ALDER REACTIONS CATALYZED BY LANTHANIDE CHLORIDES

Lanthanide chlorides have been found to catalyze the Diels-Alder synthesis of 2-butoxy-3, 4-dihydro-2H-pyran and several norbornene derivatives under mild conditions. In particular, the heavier lanthanide chlorides are very active catalysts for some (4 + 2) cycloaddition reactions. The catalyst activities and selectivities generally increase with increasing atomic number of the rare earth elements.

STUDY ON BONDING AND 4F ORBITAL EFFECT OF LANTHANIDE COMPOUNDS

The bonding and the 4f orbital effect of lanthanide elements at different valence state in their compounds have been studied by INDO method in this paper. The results obtained show that the bonding of lanthanide compounds is affected by many factors, such as valence state, ionic radius, ligand, coordinate number, space configuration etc. The strength of bonds composed of different ligands with lanthanide is distinctly different. The covalence of Ln-L bonds of lanthanide ions at high valence state in their compounds is larger than that at low valence state, The covalency at low coordinate number is larger than that at high coordinate number. Some lanthanide compounds with special configuration, besides sigma-bond, can form p(pi)-d(pi) dative bond with much overlap, which makes the Ln-L bond increase markedly. The effect of 4f orbitals on bonding is far less than that of 5d orbitals. The Ln 4f orbitals at 3 or 2 valence state may be considered to be essentially localized, while the contribution of 4f orbitals on bonding in 4 valent cerium compounds increases obviously, up to 1%.

SYNTHESIS AND X-RAY CRYSTAL-STRUCTURE OF [EU(ETA-6-C6ME6)(ALCL4)2]4 - THE 1ST CYCLOTETRAMERIC LANTHANIDE(II) COMPLEX WITH A NEUTRAL PI-LIGAND

The reaction of EuCl3, AlCl3 and C6Me6 in toluene gives the Eu(II) complex [Eu(eta-6-C6Me6)(AlCl4)2]4; X-ray crystal determination shows the molecule to be a cyclotetramer, in which the four Eu(C6Me6)AlCl4 units are connected via four groups of eta-2-AlCl4.

C-13 AND H-1 NMR STUDIES OF SOLUTION STRUCTURE OF LANTHANIDE COMPLEX WITH GLYCYL-GLYCINE

C-13 and H-1 NMR technique was used to study the interaction of Gly-Gly with heavy lanthanide cations Dy3+, Ho3+, Er3+, Tm3+ and Yb3+ in aqueous solution. The stability constants for the 1:1 and 1:2 complexes of Gly-Gly with Ho3+ and Yb3+ were determined from the titration curves of chemical shift versus concentration ratio of lanthanide to Gly-Gly. The solution structure of the Ln-Gly-Gly complex was analyzed based upon the C-13 and H-1 lanthanide induced shifts and the results show that in the complex Gly Gly is coordinated to the lanthanide ion through the carboxyl oxygens with the backbone of the ligand in an extended state.

SYNTHESIS AND CRYSTAL-STRUCTURE OF A NEW LANTHANIDE CYCLOOCTATETRAENE COMPLEX (ETA-8-C8H8)ER(MU-ETA-8-C8H8)K(MU-ETA-8-C8H8)ER(MU-ETA-8-C8H8)K(THF)4

The tetranuclear nearly-linear complex (eta-8-C8H8)Er(mu-eta-8-C8H8)K(mu-eta-8-C8H8)Er(mu-eta-8-C8H8)K(THF)4 (THF = tetrahydrofuran) is first synthesised by the reaction of benzylcyclopentadienyl erbium dichloride (PhCH2C5H4)ErCl2.3THF with cyclooctatetraenyl potassium K2C8H8 in 1:1 molar ratio in THF; a single crystal X-ray study has shown that the complex has the tetralayer-sandwich structure and that the adjacent Er3+ and K+ ions are bridged by eta-8-cyclooctatetraenyl group.

SYNTHESIS OF ALKALI-METAL HYDRIDES USING LANTHANIDE TRICHLORIDE-NAPHTHALENE AS CATALYST UNDER MILD CONDITIONS

The hydrogenation of alkali metals using lanthanide trichloride and naphthalene as catalyst has been studied. LnCl3(Ln = La, Nd, Sm, Dy, Yb) and naphthalene can catalyze the hydrogenation of sodium under atmospheric pressure and 40-degrees-C to form sodium hydride. The activities of lanthanide trichlorides are in the following order: LaCl3 > NdCl3 > SmCl3 > DyCl3 > YbCl3. Although lithium proceeds in the same catalytic reaction, the kinetic curve of the lithium hydrogenation is different from that of sodium. Lanthanide trichlorides display no catalytic effect on the hydrogenation of potassium in presence of naphthalene. The mechanism of this reaction has been studied and it is suggested that the anion-radical of alkali metal naphthalene complexes may be the intermediate for the hydrogenation of alkali metals and the function of LnCl3 is to catalyze the hydrogenation of the intermediate. The products are porous solids with high specific surface area (83 m2/g for NaH) and pyrophoric in air. They are far more active than the commercial alkali metal hydrides. The combination of these hydrides with some transition metal complexes exhibits high catalytic activity for the hydrogenation of olefins.

SYNTHESES OF BIS(TERT-BUTYLCYCLOPENTADIENYL)LANTHANOID CHLORIDE COMPLEXES AND CRYSTAL-STRUCTURES OF BIS(TERT-BUTYLCYCLOPENTADIENYL)CHLORO(BISTETRAHYDROFURAN)-PRASEODYMIUM AND BIS(TERT-BUTYLCYCLOPENTADIENYL)-CHLOROTETRAHYDROFURANYTTERBIUM

Reaction of lanthanoid trichloride with two equivalents of sodium t-butylcyclopentadienide in tetrahydrofuran affords bis(t-butylcyclopentadienyl)lanthanoid chloride complexes (t-BuCp)2LnCl. nTHF (Ln = Pr, Nd, n = 2; Ln = Gd, Yb, n = 1). The compound (t-BuCp)2PrCl.2THF (1) crystallizes from THF in monoclinic space group P2(1)/c with unit cell dimensions a = 15.080(3), b = 8.855(2), c = 21.196(5) angstrom, beta = 110.34(2)degrees, V = 2653.9 angstrom-3 and D(calcd) = 1.41 g/cm3 for Z = 4. The central metal Pr is coordinated to two t-BuCp ring centroids, one chlorine atom and two THF forming a distorted trigonal bipyramid. The crystal of (t-BuCp)2YbCl.THF (2) belongs to the monoclinic crystal system, space group P2(1)/n with a = 7.726(1), b = 12.554(2), c = 23.200(6) angstrom, beta = 97.77(2)degrees, V = 2229.56 angstrom-3, D(calcd) = 1.50 g/cm3 and Z = 4. The t-BuCp ring centroids, the chlorine atom and the oxygen atom of the THF describe a distorted tetrahedron around the central ion of ytterbium.

SYNTHESIS OF TETRAPHENYLBUTADIENE LANTHANIDE METALLACYCLES

The cyclic derivatives of transition metals have been extensively investigated in recent years since they are believed to serve as key intermediates in various homogeneous catalytic processes of olefine and alkyne metathesis. The synthesis of the title compounds has not been reported before.

Novel antifouling and antimicrobial compound from a marine-derived fungus Ampelomyces sp.

In this study, using a bioassay-guided isolation and purification procedure, we obtained 3-chloro-2,5-dihydroxybenzyl alcohol from a marine-derived Ampelomyces species that effectively inhibited larval settlement of the tubeworm Hydroides elegans and of cyprids of the barnacle Balanus amphitrite. The inhibitive effect on larval settlement was nontoxic and the EC50 of 3-chloro-2,5-dihydroxybenzyl alcohol ranged from 3.19 mu g ml(-1) to 3.81 mu g ml(-1) while the LC50 was 266.68 lambda g ml(-1) for B. amphitrite cyprids; EC50 ranged from 0.67 mu g ml(-1) to 0.78 mu g ml(-1), and LC50 was 2.64 mu g ml(-1) for competent larvae of H. elegans, indicating that inhibitive effect of this compound was nontoxic. At a concentration of 50 mu g per disc, this compound showed strong inhibitive effects on the growth of 13 out of 15 marine bacterial species tested in disc diffusion bioassay. Overall, the high inhibitory activities against bacteria and larval settlement as well as the non- or low-toxic nature of this compound to the barnacle and polychaete larvae suggest this compound could be a potent antifoulant and/or antibiotic.