Volume 50, Issue 4

The homonuclear cobalt cluster [(η 5 -Cp*)Co] 3 H 4 2 reacts with various organic and inorganic substrates with complete degradation of the cluster core to afford mainly mononuclear organometallic cobalt compounds. Thus, whereas reaction of the cluster with CO, NO or alkynes results in the retention of the Co 3 ring, the cluster reacts with Br 2 , I 2 , I 2 /CO , I 2 / P(C 2 H 5 ) 3 , CCl 4 , HCI 3 , (CH 2 ) 2 Br 2 , Hacac, CH 2 Br 2 , (C 6 H 5 CO)OOC(CH 3 ) 3 , HBF 4 , and BrCN to give mononuclear complexes or bridged dinuclear complexes without a metal-metal bond. In all cases formal oxidation of the metal center is observed. The crystal structures of six organocobalt complexes have been determined by X-ray crystallography.

Selective lactone formation from hydroxy esters can be obtained with microporous glass catalysts. By a sol-gel polycocondensation of TEOS and a cyclic phosphonate an imprinted microporous silica catalyst was prepared. The imprint molecule selected is a transition state analogue for the lactone formation from hydroxy esters. Although selective γ- and δ-lactone formation from the respective hydroxy esters was observed, control experiments revealed, that the catalytic selectivity of the lactone formation is already obtained by the micropores of the material and not associated to the imprint. The study illustrates the importance of proper control experiments for the evaluation of imprint effects in selectively catalyzed reactions.

2,5-Hexanedione was converted into the bisfulvene 2, then treated with two molar equivalents of methyllithium to yield the [4-cyclopentadienylidene-4,7,7-trimethyl-4,5,6,7-tetrahydroindenyl] dilithio compound 4. Hydrolysis, followed by treatment with acetone/pyrrolidine, gave the corresponding fulvene system 5. Reaction of 5 with methyllithium followed by treatment with ZrCl 4 furnished the ring-annulated C 1- bridged ansa-metallocene 8, bearing a tert-butyl substituent at the Cp ring, as a 1:1 mixture of two diastereoisomers. Treatment of the fulvene 5 with LiAlH 4 followed by ZrCl 4 yielded the respective isopropyl-substituted ansa-metallocene diastereomers 9a and 9b. Complex 9b was separated by fractional crystallization and characterized by X-ray diffraction. Complexes 8 and 9 provide active homogeneous Ziegler-type catalyst systems upon activation with excess methylalumoxane producing low molecular weight isotactic polypropylene with high catalyst activities.

The reaction between catalytically prepared magnesium hydride (MgH 2 *) and [TiCl 3 (THF) 3 ] in a molar ratio of 1.5:1 in THF yields a highly pyrophoric, X -ray amorphous titanium hydride precipitate with the composition [TiH 2 ·(MgCl 2 · 2 THF) 0.2 - 0.3 ] (2). This novel titanium hydride has been characterized through hydrolysis and iodolysis, as well as through thermolysis to Ti* and H 2 in the solid state and in organic solvents. 2 is slightly soluble in THF and proves itself as an active reagent in a variety of reactions.

The 13 C NMR parameters of several cyclobutabenzenes ( 1a - 1e ) and their corresponding complexes (cyclobutabenzene)M(CO) 3 (M = Cr, Mo, W, 2 - 4 ) are presented and discussed. Two cyclobutabenzenes 1b and 1d and their chromium tricarbonyl complexes 2b and 2d have been examined in greater detail: the signal assignments have been confirmed by 2 D-INADEQUATE and the one bond coupling constants 1 J( 13 C , 13 C) measured at natural abundance using 1 D-INADEQUATE . Although the results provide no insight into why the chromium complex of 1,2 - dioxocyclobutabenzene (1e) is much more reactive at the keto groups than 1e itself, they do reveal a weak but not negligible alternation of the carbon s-character in the C - C bonds of the 6-membered rings both in the free cyclobutabenzenes and in the complexes, thus providing evidence for slight bond fixation (Mills-Nixon effect).

The hydrovinylation of styrene can be catalyzed by the addition of phosphane-modified Ni(II) compounds with high reactivity and enantioselectivity if the azaphospholene 1 is used as P-component of the catalysts. Until recently the industrial applications of 1 have been hampered by its difficult synthesis. To search for easier to synthesize, but equally well catalyzing derivatives of 1 a molecular modelling study was carried out. Based on already experimentally tested and structurally characterized azaphospholenes a model is developed, which not only leads to a better understanding of the catalytic process and but also to a relatively easy way to predict catalytic properties in these systems. Using an extended, customized valence force field several new derivatives of 1 have been tested. Their predicted and experimentally determined catalytic properties are in good agreement. The X-ray structures of the phenyl-substituted, monomeric azaphospholene 13, which hitherto results in the second best catalyst, and of its precursor 19 are presented.

The structure of the compounds formed upon reacting Fe(Pr i 2 P(CH 2 ) n PPr i 2 )Cl 2 (n = 1-3) and active-Mg with acyclic and cyclic 1,3-, 1,4- and 1,5-dienes depends upon the nature of the diene and upon the length of the methylene-chain bridging the two P-atoms of the bidentate ligand. For example, isoprene reacts to give either (η 4 -isoprene) 2 FePPr i 2 C 2 H 4 PPr i 2 or (η 4 -isoprene)Fe(Pr i 2 PC 3 H 6 PPr i 2 ) while the products of the reaction with 1,5-hexadiene are (η 5 -1-methylpentadienyl)Fe(Pr i 2 PC 2 H 4 PPr i 2 )H or (η 2 ,η 2 -1,5-hexadiene)Fe(Pr i 2 PC 3 H 6 PPr i 2 ). The crystal structures of the last two compounds have been established by X-ray diffraction. The penultimate species catalyses the linear dimerization of 1,5-hexadiene.

Complex formation equilibria of diethyltin(IV) with five N-D-gluconylamino acids in aqueous solution (I = 0.1 M, NaClO 4 ) were studied and the stabilities of the species were determined by potentiometric titrations. Diethyltin(IV) complexes of α-amino acid derivatives are water-soluble in the physiological pH range, while in the presence of N-D-gluconyl-β-alanine a precipitate is formed, which dissolves with increasing pH. 13 C NMR measurements showed that in the N-D-gluconyl-α-amino acid complexes the ligand is coordinated through its deprotonated carboxylate oxygen, amide nitrogen and C(2)-hydroxy group, while for the soluble N-D-gluconyl-β-alanine complex the ligand is coordinated via the deprotonated carboxylate and C(3)-, C(4)-, C(5)-hydroxy groups. Mössbauer measurements reflected the geometry of the complexes formed.

The photochemistry of bis(8-quinolinolato)Cu(II), Cu(ox) 2 , and bis(8-quinolinethiolato)- Cu(II), Cu(tox) 2 , has been studied by continuous photolysis in aprotic solvents. The charge transfer irradiations induce the oxidation of the ligand and the reduction of copper(II) to copper(I). These assignments are supported by EPR data and UV-Vis spectra of the complexes. The photochemical properties of copper(II) complexes are discussed in terms of the population of charge transfer to copper-excited states. Both complexes show solvent-dependent photochemistry when irradiated in CHCl 3 and in toluene. The photoproducts of Cu(tox) 2 in CHCl 3 are partially reconverted into the initial complex by thermal reaction, while photoreactions of Cu(ox) 2 lead to secondary photolytic processes.

The complexation of sodium ion with 1,4,7,10-tetraoxacyclododecane (12-crown-4) and 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6) has been studied by titration calorimetry in pyridine (PY) containing 0.1 mol dm -3 (C 2 H 5 ) 4 NClO 4 as a constant ionic medium at 25 °C. The calorimetric titration data were well explained in terms of the formation of the [Na(12-crown-4)] + , [Na(12-crown-4) 2 ] + , and [Na(18-crown-6)] + complexes, and their formation constants, reaction enthalpies, and entropies were determined. The formation of [Na(18-crown-6)] + is much pronounced in PY over N,N-dimethylformamide (DMF) and water, and the stability order is PY > DMF > water. The enthalpy values for the formation of [Na(18-crown-6)] + are all negative in PY, DMF, and water, and increase in the order PY < DMF < water. The complexation is the least exothermic in water, though sodium ion is the most weakly solvated in water. This is because 18-crown-6 is much stabilized in water by forming hydrogen bonds with water molecules. Despite the stronger electron pair-donating ability of PY than DMF, the complexation is more exothermic in PY than in DMF. This is ascribed to the different solvation number of the sodium ion in P Y and DMF, i.e., the sodium ion is coordinated with a smaller number of solvent molecules in the former solvent than in the latter.

Six dinuclear copper(II) complexes have been prepared, Cu 2 (taet)(plam) 2 X 2 where taet = 1,1,2,2-tetraacetylethanediide, plam = N-alkylated polyamine such as tmen = N,N,N′,N′-tetramethylethylenediamine or pmdt = N,N,N′,N′,N′-pentamethyldiethylenetriamine, X = a monovalent anion such as ClO 4 - , NO 3 - or Cl - . These complexes are classified into two categories from the results of electronic spectra, IR spectra, and X-ray single crystal structure analysis as follows: (1) 4-coordinate-4-coordinate dinuclear, [Cu 2 (taet)(tmen) 2 ]X 2 (where X = ClO 4 - or NO 3 - ), (2) 5-coordinate-5-coordinate dinuclear, [Cu 2 (taet)(tmen) 2 Cl 2 ], and [Cu 2 (taet)(pmdt) 2 ]X 2 (where X = ClO 4 - , NO 3 - , or Cl - ). The crystal structure of Cu 2 (taet)(tmen) 2 (ClO 4 ) 2 · H 2 O (1) has been determined by the single crystal X-ray diffraction technique; monoclinic space group P2 1 /a with a = 26.478(3), b = 8.744(1), c = 15.601(3) Å, β = 106.195(9)°, and V = 3468.9(8) Å 3 for Z = 4. The final agreement factors are R = 0.097 ( R w = 0.099). The geometry of each Cu(II) moiety in the dinuclear cation (1) is 4-coordinate square planar with a N 2 O 2 donor set. This tmen-dinuclear complex exhibits a very weak C u (II)-Cu (II) interaction (J = -0.5 cm -1 ), and shows characteristic ESR spectra with seven hyperfine peaks in 1,2-dichloroethane solution at room temperature. This is not found for the corresponding pmdt-dinuclear complex. All complexes obtained in this study are very soluble in many organic solvents. The tmen-dinuclear complexes show pronounced solvatochromic behavior-dependent on the solvent donor properties. This is not found for the corresponding pmdt-dinuclears, which are stable as 5-coordinated species.

Thermochromism was observed for an aqueous solution containing zinc(II) and mercury( II) cations and N-p-nitrobenzyl-5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin anion (NO 2 Bz(Htpps) 4- ) in the temperature range 10 to 70 °C. The equilibrium constants and the thermodynamic parameters of Zn(NO 2 Bztpps) 3- and Hg(NO 2 Bztpps) 3- have been determined spectrophotometrically to elucidate the thermochromism at 10, 15, 20, 25 and 30 °C in 0.1 mol dm -3 NaNO 3 . The protonation and metalation constants of NO 2 Bz(Htpps) 4- are defined as K 2 = [H 2 P][H + ] -1 [HP] -1 , K 3 = [H 3 P][H + ] -1 [H 2 P] -1 and K MP = [M P][H + ][M 2+ ] -1 [HP] -1 , where HP and MP denote the free base form of the prophyrin and the metalloporphyrins of zinc(II) and mercury(II), respectively. Charges of the prophyrin and metalloporphyrins are omitted for simplicity. The following values were found: logK 2 = 7.75 ±0.02 (25 °C), ΔH°/kJmol -1 = -21.2±0.5 and ΔS°/Jmol -1 K -1 = 77±1, logK 3 = 2.55±0.02 (25 °C), ΔH°/kJmol -1 = -25±0.8 and ΔS°/Jmol -1 K -1 = -35±3 and log K ZnP = 0.63±0.03 (25 °C), ΔH°/kJmol -1 = 31.0±0.8 and ΔS°/Jmol -1 K -1 = 116±3, logK HgP = 6.22±0.03 (25 °C), ΔH°/kJmol -1 = 4.5±0.7 and ΔS°/Jmol -1 K -1 = 134±2. The distribution curve calculated from the thermodynamic parameters sufficiently agrees with the observed metal exchange reaction between the metalloporphyrins.

New trinuclear rhodium(III) complexes, [Rh 3 (μ 3 -O)(μ-CH 3 COO) 6 (L) 3 ] + (L = imidazole (Him), 1-methylimidazole (Meim), and 4-methylpyridine (Mepy)) have been prepared. The Him, Meim, and Mepy complexes show reversible one-electron oxidation waves at E 1/2 = +1.12, +1.12, and +1.28 V vs Ag/AgCl, respectively, in acetonitrile. Electronic absorption spectra of the one electron oxidized species of these complexes and [Rh 3 (μ3-O)(μ-CH 3 COO) 6 (py) 3 ] + (py = pyridine) (E 1/2 = +1.32 V ) were obtained by spectroelectrochemical techniques. While the Rh 3 (III,III,III) states show no strong visible absorption, the Rh 3 (III,III,IV ) species give a band at ca. 700 nm (ε = 3390-5540 mol dm -3 cm -1 ). [Ir 3 (μ 3 -O)(μ-CH 3 COO) 6 (py) 3 ] + with no strong absorption in the visible region, shows two reversible one-electron oxidation waves at +0.68 and +1.86 V in acetonitrile. The electronic absorption spectrum of the one-electron oxidized species (Ir 3 (III,III,IV )) also shows some absorption bands (688 nm (ε, 5119), 1093 (2325) and 1400 (ca. 1800)). It is suggested that the oxidation removes an electron from the fully occupied anti-bonding orbital based on metal-dπ-μ 3 -O-pπ interactions, the absorption bands of the (III,III,IV ) species being assigned to transitions to the anti-bonding orbital.

Condensation of 1,2-diaminopyridinium iodides with tris(dimethylamino)phosphine gives [1,2,4,3]triazaphospholo[1,5-a]pyridines 2a - d . Diethylamine adds to the N=P bond of 2a, b only if the phosphorus is oxidized at the same time. Hydrolysis of 2a opens the triazaphosphole ring at its 2,3-bond.

A novel C-28 tetraglycoside of quillaic acid (1) has been isolated from Gypsophila capillaris. The structure was elucidated by 1 D NMR (NOE difference, DEPT, selective 13 C{ 1 H} INEPT), 2D NMR ( 1 H, 1 H and 1 H, 13 C COSY, 1 H, 1 H, 1 H RELAY, ROESY and TOCSY) and other spectroscopic and chromatographic evidences. Conformational dynamics within the tetrasaccharide part were estimated from NOE responses and ROESY peaks.

The racemic mixtures of the muscarinic antagonists cyclohexyl(phenyl)(2-pyrrolidinoethyl)silanol (sila-procyclidine, rac-1), cyclohexyl(hydroxymethyl)phenyl(2-piperidinoethyl)-silane (rac-2) and cyclohexyl(hydroxymethyl)phenyl(2-piperidinoethyl)germane (rac-3) were resolved by analytical liquid chromatography (HPLC) using chemically modified cellulose (1) or amylose (2, 3) as the chiral stationary phase. This chromatographic method was used for the quantitative determination of enantiomeric purity of the (R)- and (S)-enantiomers of 1 - 3 , which were obtained by preparative resolution with chiral auxiliary agents. Furthermore, the enantiomeric purity of these samples was established by 13 C NMR studies using chiral shift reagents. According to these studies, the resolved antipodes of 1 - 3 (obtained by preparative resolution) were almost enantiomerically pure [HPLC: ≥ 98.2% ee ((R )-3) to 99.4% ee ((R)-1, (S)-1); NMR: ≥ 97% ee].

[TeCl 2 (NPMe 3 ) 2 ] 2 has been prepared by the reaction of TeCl 4 with Me 3 SiNPMe 3 in acetonitrile solution. Tlie compound forms white moisture sensitive crystals which have been characterized by IR spectroscopy and by a crystal structure determination. Space group P2 1 /c, Z = 2, structure solution with 3510 independent reflections, R = 0.029. Lattice dimensions at - 70 °C; a = 1206.0(9); b = 1054.7(7); c = 1156.0(6) pm; β = 99.27(5)°. [TeCl 2 (NPMe 3 ) 2 ] 2 forms centrosymmetric molecules via TeCl 2 Te bridges with bond lengths Te-Cl of 267.2 and 366.9 pm, the longer one being in trans-position to one of the terminally bounded (NPMe 3 - ) groups. The TeN bond lengths of 190.1 and 192.6 pm are unusually short.

Single crystals of (Cu 0.22 Mg 0.78 )BaNd 2 Mo 4 O 16 have been prepared by crystallization from melts and investigated by X-ray methods. The compound crystallizes monoclinically, space group C 6 2h - C12/c1, Z = 4, a = 5.351(1), b = 12.891(2), c = 19.391(4) Å,β = 90.899(14)° and is isotypic to CuKHo 2 Mo 4 O 16 . The crystal structure is dominated by BaO 10 and NdO 8 polyhedra forming a three-dimensional polyhedra network, which is filled by axially distorted (Cu,Mg)O 6 octahedra and MoO 4 tetrahedra.

Single crystals of NaSr 3 RuO 6 have been prepared in closed silver tubes and investigated by X-ray techniques. This compound crystallizes with trigonal (rhombohedral) symmetry, space group D 6 3d - R3̅c , a = 9.6069(8), c = 11.513(2) Å, Z = 6, and is isotypic to compounds of the Sr 4 PtO 6 type. The crystal structure is discussed with respect to related compounds with partial replacement of alkaline earth elem ents by sodium and copper.

Single crystals of Ba 9 Ru 3.2 Mn 5.8 O 27 have been prepared by flux techniques. X-ray four circle diffractometer measurements led to trigonal (rhombohedral) symmetry, space group D 5 3d - R3̄̄̄m , a = 5.7043(5), c = 21.255(4) Å , Z = 1. This phase is isotypic to BaRuO 3 . The crystal structure and the occupation of the M 3 O 12 triple octahedra by ruthenium and manganese are discussed with respect to other oxides containing M 3 O 12 groups in an ordered and disordered way.

The reaction of hydrogen peroxide with all-(E)-retinol (1) catalyzed by (meso-tetraphenylporphinato) iron(III) led to the formation of 4-hydroxyretinol (2), 4-oxoretinol (3), 5,8-epoxyretinol (4), 5,6-epoxyretinol (5), 3-dehydroretinol (6), all-(E)- and 12-(Z)-retroretinol (7/7a) as well as all-(E)- and 12-(Z)-anhydroretinol (8/8 a) as major non-volatile products. The conversion products were characterized by comparison of their chromatographic (HPLC) and spectroscopic data (UV; MS; 1 H and 13 C NMR) with those of synthesized reference compounds. The observed product formation supports the hypothesis of a C4 centered radical as the key intermediate of all-(E)-retinol conversion.

From the electron and proton transfer equilibria network of quinones in solution a novel intermediate can be prepared by deprotonation of 2,5-bis(trimethylsilyl)hydroquinone to its monoanion using sodium metal. The sodium salt crystallizes in polymer strings connected via O ⊖ ···(H)O hydrogen bridges, which are capped additionally by twofold dimethoxy-ethanesolvated Na ⊕ countercations. The single crystal structure determination reveals one of the shortest O ⊕ ··· HO distances observed so far of only 246 pm. MNDO calculations further confirm the assignment of hydroquinone monoanion building blocks in the polymer chain. For structural comparison as well as for attempts of its sodium reduction, 2,5-bis(trimethylsilyl)-p- benzoquinone has been synthesized. Its single crystal structure is reported, which does not show any cyanine distortion.

Chelate complexes of 1,2-dimesitoylbenzene radical anion with alkali metal cations exhibit in aprotic solution extremely large ESR /ENDOR metal coupling constants. For rationalization, structures of both the neutral molecule (H 3 C) 3 H 2 C 6 - CO - C 6 H 4 - CO - C 6 H 2 (CH 3 ) 3 , in which the two carbonyl groups are twisted out of the benzene ring plane by dihedral angles of ± 3̄7̄°, and a sodium contact ion quadruple have been determined. One of the dimers [dimesitoylbenzeneH ⊖ (Na ⊕ H 2 N H 2 C - CH 2 NH 2 )] 2 , although generated by Na metal mirror reduction of 1,2-dimesitoylbenzene in aprotic DME solution with added ethylendiamine for better electron transfer, surprisingly contains two 245 pm short (!) hydrogen bridges ⊖ O ··· (H)O and in addition two solvation bridges e ⊖ O ··· Na ⊕ (H 2 NH 2 C - CH 2 NH 2 ) ··· O ⊖ . Results of MNDO calculations based on the experimental coordinates support the proposed concept.

Bis(arylsilyl)arenes such as bis(p-tolylsilyl)benzene and bis(p-anisylsilyl)naphthalene are available from in situ Grignard reactions of the corresponding haloarenes, arylchlorosilanes and magnesium in tetrahydrofuran. Treatment of these products with one equivalent of trifluoromethanesulfonic (triflic) acid at low temperatures leads to arylsilyl(trifluoromethylsulfonatosilyl) arenes, which can be converted into arylsilyl(silyl)arenes using LiAlH 4 . The regioselectivity of the Si - C cleavage is surprisingly high. Any of the first dearylation steps is faster then the consecutive steps. Ortho, meta and para substituted p-tolylsilyl(silyl)benzenes, 1,4-dibromo-2-(p-tolylsilyl)-5-(silyl)benzene, and 1-(p-anisylsilyl)-8-(silyl)naphthalene have thus been obtained in good to moderate yields. These compounds can serve as starting materials for monofunctional arylsilanes with a tailored structure. The crystal structure of 1-(p-anisylsiIyI)-8-(siIyl)naphthalene has been determined by single crystal X-ray diffraction.

CaMg 2 N 2 (trigonal, P3̄ m 1 (Nr. 164); a = 354.046(1), c = 609.079(2) pm; Z = 1) is isotypic to the anti-La 2 O 3 structure with octahedral and tetrahedral coordination for Ca 2+ and Mg 2+ ions, respectively. The compound has been prepared by the reaction o f the binary nitrides Ca 3 N 2 and Mg 3 N 2 (molar ratio 1:2) in a tungsten crucible under a pure nitrogen atmosphere at 1050 °C. The formation of the solid CaMg 2 N 2 may be interpreted in analogy to reactions o f related oxides as an acid-base reaction between the binary nitrides with different coordination tendencies of Ca 2+ and Mg 2+ ions. An analysis of the binary aristotype anti-La 2 O 3 indicates that this structure is predisposed for building ternary phases.

The crystal structure of [P(C 6 H 5 ) 4 ][B 6 H 6 (CH 3 )] has been determined by single crystal X-ray diffraction analysis; triclinic space group P 1̄ with a = 7.408(2), b = 11.887(3), c = 14.4486(9) Å , α = 80.013(12), β = 79.421(10), γ = 88.85(2)°. The additional H atom could be refined with B - H distances between 1.21 and 1.31 Å above one of the facettes of the B 6 octahedron adjacent to the methyl group. The IR and Raman spectra of the ueprotonated Cs salts of the six isotopomers [B 6 H 5 (CH 3 )] 2- , [B 6 H 5 (CD 3 )] 2- , [B 6 H 5 ( 13 CH 3 )] 2- , [B 6 D 5 (CH 3 )] 2- , [B 6 D 5 (CD 3 )] 2- and [B 6 D 5 ( 13 CH 3 )] 2- exhibit characteristic shifts of their vibration bands. Using the crystallographic data a normal coordinate analysis has been performed, based on a general valence force field. With a set of 14 force constants (e.g. f d (BB ) = 1.80, f d (BC ) = 3.70, f d (BH ) = 3.17, f d (CH ) = 4.62 mdyn/Å) good agreement between observed and calculated frequencies o f all D and 13 C isotopically labeled derivatives has been achieved. The potential energy distribution on the force constants reveals strong vibrational couplings of the boron cage with the substituents. The B - C stretching vibration o f the CH 3 group is observed in the region 1142-1153 cm -1 , for the CD 3 substituent at higher frequencies of 1168-1179 cm -1 .

Single crystals of the compound CuTm 2 [B 2 O 3 ] 2 were obtained by a B 2 O 3 flux technique. The compound contains a hitherto unknown metaborate anion with the formula 2 ∞ [B 2 O 5 ] 4- . It crystallizes in the monoclinic space group C 5 2h - P2 1 /c with a = 452.18(7); b = 720.0(2); c = 929.2(5) pm; β = 90.16(5)°; Z = 2. The metaborate layers consists of four and eight membered rings of edge-sharing BO 4 -tetrahedra resembling the complex anion in the isotypic gadolinite structure of FeY 2 [BeSiO 3 ] 2 . The layers are connected via copper-centered elongated oxygen octahedra and slightly distorted thulium-centered tetragonal oxygen antiprisms.

The sterically highly shielded and monomeric tetrakis[bis(trimethylsilyl)methyl]dialuminoxane R 2 Al - O - AlR 2 (R = CH(SiMe 3 ) 2 ) 1 forms 1:1 and 1:2 adducts on treatment with trimethylamine oxide. Both products have been characterized by crystal structure determination. Contrary to the linear educt 1, the complexes show bent Al - O - Al groups with bond angles of 162.3 and 161.4°. The mono adduct 2 has three- and four-coordinated Al atoms with a very short Al - O bond between the bridging oxygen and the coordinatively unsaturated Al atom (168.7 pm), possibly indicating a π-interaction. The second bond of the dialuminoxane fragment is lengthened to 175.3 pm and represents a “normal” Al - O distance. The Al - O bond to the amine oxide ligand (184.6 pm) lies within the range o f dative Al - O bonds. As shown by NMR spectroscopy the unsymmetrical structure is preserved in toluene solution up to 90 °C. In the bis(amine-oxide) adduct 3 both A l atoms are four-coordinated with very similar inner Al - O bond lengths o f 173.6 pm.

The new bistetrazole 13 has been obtained by subsequent formation of the two heterocyclic units. In methanolic solution 13 reacts with zinc(II) acetate to yield the pseudo-meso-1 D-coordination polymer [ZnL 2 (MeOH)] n (n = ∞) 14. The structure of 14 was established by single crystal X-ray diffraction. The generation of the polymeric chain 14 is understandable, if intermediate formation of coordinatively unsaturated zinc(II) buildingblocks (Δ)-15 and (Λ)-15 is assumed. Alternating linkage of the self-complementary chiral monomers 15, across one cyanofunction each, leads to 14 with zinc being essentially octahedrally coordinated. Compared with polymeric compounds of similar bridging ligands, the Zn ··· N≡C-distance in 14 (225,7 pm) is short.

Decacarbonyldirhenium (1) reacts upon UV irradiation with allene (2), 1,2-butadiene (3) and 2,3-pentadiene (4) preferentially by CO substitution and oxidative rearrangement to the corresponding enneacarbonyl-μ-η 1:3 -endiyl-dirhenium complexes 5, 9, and 15 and to the octacarbonyl-μ-η 2:2 -allene-dirhenium complexes 6, the stereoisomers 10, 11, and 16. At elevated temperature 5, 9, and 15 loose CO and yield by a reductive rearrangement also the complexes 6, 10, 11, and 16. In addition to these main products, depending upon the allene derivative used, various by-products are obtained. By-products of the reaction o f 1 with 2 are octacarbonyl-μ-η 3:3 -(2,3-dimethylene-buta-1,4- diyl)dirhenium (7) and μ-η 2:2 -allene-hexacarbonyl-μ-η 1:3 -1-propene-1,3-diyl-dirheniurn (8). The photo reaction of 1 with 3 yields, in addition to 9-11, tetracarbonyl-η 3 -(E-5-ethylidene- 4-methyl-2-cyclopenten-1-yl)rhenium (12) and tetracarbonyl-η 3 -(Z-5-ethyliden-4- methyl-2-cyclopenten-1-yl)rhenium (13) as a mixture of isomers. 1 and 4 form the by-products tetracarbonyl-η 3 -(EZ-3-penten-2-yl)rhenium (17), tetracarbonyl-η 3 -(EE-3-penten-2-yl)rhenium (18) and heptacarbonyl-μ-η 1:2:1:2 -(4,5-dimethyl-2,6-octadiene-3,6-diyl)dirhenium (19) with an unusually bridging and chelating ligand. The constitutions of the reaction products have been concluded from the IR and 1 H NMR spectra. For 19 the crystal and molecular structure has been determined by X-ray diffraction analysis.

Details on a synthesis of the trisaccharide α-D-Glc(1→6)-β-D-Glc(1→6)-D -Glc are reported. The O-glycosidic linkages were constructed using the sulfoxide glycosylation reaction. This approach proves to be a rapid glycosylation method leading to high yield and good selectivity.

A new 13-Aza-4,4,8,8,12,12-hexamethyl-2,6,10-trioxatricyclo[7,3,1,0 5,13 ]tridecane synthesis and the crystal structure are reported. It crystallizes in the monoclinic space group P2 1 /n with a = 1201.9(1) pm, b = 1436.6(1) pm, c = 1726.2(2) pm, β = 90.74(1)° and Z = 8.

PS-PEG tentacle polymers are modified for the synthesis of oligonucleotides covalently bound to polyethylene glycol (P E G ) at their 3′-position by the solid phase method without additional steps. The average stepwise coupling rates and overall yields are in the range of standard oligonucleotide synthesis. Oligonucleotides and phosphorothioates up to 20 nucleotides, modified with hexaethylene glycol (H E G ), PEG 400 and PEG 1500 , are synthesized in this manner. The products are characterized by capillary electrophoresis and electrospray mass spectrometry (ES-MS). These new methods are very efficient for purity control as it is required for potential antisense drugs.

A simple method for the synthesis of substituted oxazolo[3ʹ,2ʹ: 1,2]pyrido[3,4-b]indoles from 3,4-dihydro-β-carboline and α-hydroxy-γ-butyrolactones is described.

Single crystals of LiBa 2 Cu 3 O 6 have been prepared by recrystallization from melts in a stream of dry Argon as well as by spontaneous CO 2 - LASER heating. It crystallizes with orthorhom bic symmetry, space group D 23 2h - Fmmm, a = 8,219(2), b = 11,520 (2), c = 14,284(3) Å, Z = 8. The crystal structure is isotypic to NaBa 2 Cu 3 O 6 .

The title compound [(η 5 -tBu 3 Cp)CoBr] 2 1 is prepared in a one pot reaction starting from 1,2,4- tBu 3 -cyclopentadiene followed by metallation and by reaction of the resulting tBu 3 Cp - K + anion salt with anhydrous CoBr 2 in THF. 1 was isolated from this reaction in 78% yield as black crystals. 1 reacts with LiAlH 4 in THF at 0 °C. Subsequent alcoholysis of the crude reaction mixture with ethanol at -78 °C gives the novel trihydride cluster [(η 5 -tBu 3 Cp)Co] 2 H 3 2 in 58% isolated yield as black crystals. 2 has been characterized by 1 H NMR, ESR, MS, and IR spectroscopy, as well as by elemental analysis.

Bis(fluorodiisopropylsilyl)amine [(Me 2 HC) 2 SiF] 2 NH (1) reacts with the disodium salt of catechole or the disodium salt of resorcinol in a molar ratio 1:1 to give the seven-membered heteraphane [HN(Me 2 HC) 2 SiO] 2 C 6 H 4 (2) resp. the 16-membered heteraphane [HN(Me 2 HC) 2 SiOC 6 H 4 OSi(CHMe 2 ) 2 ] 2 (3). The chain-like compound [(Me 2 HC) 2 SiFNHSi(CHMe 2 ) 2 O] 2 C 6 H 4 (4) is obtained by the reaction of 1 with disodium resorcinolate.

The reaction of 6-phenyl-3-pentafluorophenoxy-tetrafluorocyclohexa- 2,4-dien-1-one (1) with one equivalent of triphenylphosphane leads to the spectroscopically detectable 5-phenyl-4-pentafluorophenoxy- 3,3,6,6-tetrafluoro-2-triphenylphosphoranylidene- 4-cyclohexen-1-one (2), which upon hydrolysis or reaction with hydroxyl groups of the glass surface yields 5-phenyl-4-pentafluorophenoxy- 6,6-difluoro-2-triphenylphosphoranylidene- 4-cyclohexene-1,3-dione (3). The structure of 3 was determined by NMR measurements and an X-ray diffraction study.

The structure of [Et 4 N] 2 2+ [TeI 6 ] 2- , the first tetraalkyl ammonium salt to contain the almost regular octahedron of a discrete [TeI 6 ] 2- anion, has been determined by single crystal X-ray diffraction studies. It crystallizes in the monoclinic space group C2/c with a = 18.757(3), b = 11.578(2), c = 15.447(2) Å, β = 109.380(10)°. The [TeI 6 ] 2- anion has Te - I bond distances in the range of 2.845 to 2.948 Å and I - Te - I bond angles in the range of 89(1) to 90.1(1)°.

3-Amino-3-deoxy sugars [1] are essential substructures of a wide variety of biologically active natural products exemplified in aminocyclitols, [2] macrolides [3] or anthracyclin antibiotics [4], With this respect, the transformations of common and readily available carbohydrates are of special interest. In this communication we want to line out a short route for the incorporation of a vicinal cis hydroxyl-amino function in the pyranose moiety.

The solid-state structure of N,N-dibenzylhydroxylamine (1) has been determined by single crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P 2 1 /n with four formula units in the unit cell. N,N-dibenzylhydroxylamine dimerizes to give N 2 O 2 H 2 sixmembered rings as a result of the formation of two hydrogen bonds O - H ··· N in the solid state.