Volume 60, Issue 6

Well-crystallized copper carbodiimide, CuNCN, was synthesized by the slow oxidation of a copper(I) cyanamide precursor under aqueous conditions. The X-ray powder data evidence the orthorhombic system and space group Cmcm with a = 2.9921(1), b = 6.1782(1), c = 9.4003(2) Å , V = 173.769(5) Å 3 and Z = 4. There is a strongly distorted octahedral Cu 2+ coordination reflecting a typical first-order Jahn-Teller effect, with interatomic distances of 4×Cu-N = 2.001(2) Å and 2×Cu-N = 2.613(3) Å ; the NCN 2− unit adopts the carbodiimide shape with C-N = 1.227(4) Å . Despite the formal d 9 electron count of Cu 2+ , CuNCN exhibits a small temperature-independent paramagnetism and is likely to be a metallic conductor.

Treatment of the nido-2,3-Et 2 C 2 B 4 H 4 2− dianion (1) with monoboron reagents led to closo-C 2 B 5 carborane derivatives with functional substituents at the inserted apical boron atom. The reactions of 1 with BX 3 (X = Br, I) afforded the corresponding closo-1-X-2,3-Et 2 C 2 B 5 H 4 (2a,b), and with PhCΞCBcat (cat = O 2 C 6 H 4 ) produced the alkynyl-substituted closo-1-CΞCPh-2,3-Et 2 C 2 B 5 H 4 (2c). Pd-catalyzed Negishi-type cross-coupling reactions of 2b with RCΞCZnCl at room temperature gave the corresponding closo-1-CΞCR-2,3-Et 2 C 2 B 5 H 4 derivatives 2d-f, R = SiMe 3 , Me, and tBu, respectively. Compound 3 with two C 2 B 5 moieties linked via a C=C unit was obtained by a similar boron incorporation reaction with cis-Cl 2 B 5 (Et)C=C(Et)BCl 2 . The reactions of 2c,d with Co 2 (CO) 8 afforded the dicobaltatetrahedrane-substituted carboranes 4c and d, in which the clusters C 2 B 5 and Co 2 C 2 are connected by a B-C bond. Compounds 4c,d lost the apical boron on wet silica gel or sand to give the nido-C 2 B 4 -C 2 Co 2 compounds 5c,d. Formation of the carboranyl-substituted (η 5 - C 5 H 5 )Co(cyclobutadiene) complex 6c was observed in the reaction of 2c with (η 5 -C 5 H 5 )Co(C 2 H 4 ) 2 . The composition of the products follows from NMR and MS data.

Surface modification of pre-dried spherical silica nano-particles with diameters of 235 nm and 10 to 20 nm and of commercially available non-spherical silica materials using various aminoalkyltrialkoxysilanes and α-ω-bis(alkoxysilyl)organyls (organyl = alkanediyl, aminoalkanediyl, polyether, polysiloxane) has been performed in suspension in solvents with water. The quantity of water has a dominating influence, as compared to the amounts and the ratios of silanes employed, on the surface morphology of the modified silicas. The morphologies observed range from weakly linked aggregates of spherical particles to large agglomerates covered by thick irregular layers of organopolysiloxane, as demonstrated by scanning electron microscopy. These carriers can be modified further with organoaluminium compounds to yield heterogeneous cocatalysts for the polymerization of ethylene.

Surface modified silica were reacted with different aluminiumalkyls AlR 2 R’ (R = Me, Et, i-Bu, R’ = H, Me, Et, i-Bu), oligomeric methylaluminoxane (MAO) and combinations of both, to yield heterogeneous cocatalysts. These cocatalyts were employed to polymerize ethylene using zirconocene dichloride as the catalyst. The polymerization activity profiles have been recorded and compared with the information gained from the scanning electron microscopy (SEM) images of the polymers. The fragmentation of the heterogeneous cocatalyts upon polymerization has been demonstrated. The degree of fragmentation and the polymerization activity depend on the preparation of the silica supports and on the preparation of the heterogeneous cocatalysts using these supports. The most reactive, fragmentable heterogeneous cocatalysts show polymerization activities slightly higher than MAO in homogeneous solution and almost 1.5 times higher than commercially available MAO on silica (=MAO on Sylopol).

The solvent-free dodecahydro-closo-dodecaborate chlorides M 3 Cl[B 12 H 12 ] (M + = Rb + , Cs + ) and bromides M 3 Br[B 12 H 12 ] (M = K + −Cs + , NH 4 + ) of the heavy alkali metals are easily accessible by recrystallization of the corresponding M 2 [B 12 H 12 ] salts from aqueous solutions of the respective alkali-metal chlorides (MCl) or bromides (MBr). After precipitation colourless, polyhedralshaped single crystals were obtained and characterized by X-ray diffraction at room temperature. The compounds are all isostructural and crystallize in the trigonal space group R3̅m with Z = 3 (Rb 3 Cl[B 12 H 12 ]: a = 1009.73(7), c = 1139.14(9) pm; Cs 3 Cl[B 12 H 12 ]: a = 1038.02(7), c = 1179.59(9) pm; K 3 Br[B 12 H 12 ]: a = 1002.34(7), c = 1117.68(9) pm; (NH 4 ) 3 Br[B 12 H 12 ]: a = 1015.61(7), c = 1138.70(9) pm; Rb 3 Br[B 12 H 12 ]: a = 1016.89(7), c = 1141.82(9) pm; Cs 3 Br[B 12 H 12 ]: a = 1045.53(7), c = 1185.47(9) pm). Their structures are best described as a trigonally distorted variant of an anti-perowskite arrangement, the anti-LaAlO 3 -type structure. Together, the quasi-icosahedral [B 12 H 12 ] 2− cluster anions and the M + cations build up a cubic close-packed host structure where the halide anions (X − ) occupy all those octahedral interstices which are exclusively formed by the cations. The thermal decomposition of the salts was investigated by thermal analysis with DTA/TG methods in the temperature range between 30 and 1200 °C. The solid salts were also characterized using IR and Raman spectroscopy. The observed splitting of the B−H and B−B absorption bands clearly indicates a loss of symmetry of the quasi-icosahedral dianionic [B 12 H 12 ] 2− clusters.

The compound {[Ba 6 (Phen) 12 (CF 3 COO) 6 {Fe(CN) 6 } 2 (H 2 O) 8 ]· 6 H 2 O}n (1) (Phen = 1,10-phenanthroline) has been synthesized and structurally characterized. In the crystal structure, the two consecutive Ba centres are bridged through trifluoroacetate groups and also via cyano groups of [Fe(CN) 6 ] 3− and form the zigzag chain resulting the formation of 24-membered ring structure. The Ba-centres are 8-fold coordinated with distorted cubic geometry. Six H 2 O molecules per asymmetric unit remain in the structure without any direct interaction with the metal atoms but they act in hydrogen bond formation.

Low-temperature X-ray structures of the following di(4-X-benzenesulfonyl)amines, HN(SO 2 -C 6 H 4 -X) 2 , are compared in order to study the effects of the 4-substituents on the molecular packings: X = F (1, monoclinic, C2/c, Z′ = 1), X = Cl (2, monoclinic, C2/c, Z′ = 1/2, N-H bonds lying on twofold rotation axes), X = Me (3, orthorhombic, Pbca, Z′ = 1), X = Br (4A, monoclinic, P2 1 /c, Z′ = 1), X = Br (4B, monoclinic, P2 1 /c, Z′ = 2). As a common feature, the molecules of the halogen compounds, including two polymorphs of 4, are associated into catemers by strong hydrogen bonds of the type N-H···O in 1, 4A and 4B or N-H(···O) 2 in 2. These molecular chains are assembled in the crystal structures via different packing modes, which underline the well-known correlation between the atomic number of halogen atoms and their propensity to form halogen bonds. Thus, the structure of 1 is devoid of short C-F···O/N contacts, but close F···F contacts are tolerated, whereas in 2 each catemer is connected to four parallel congeners by long and bifurcated C-Cl(···O) 2 bonds, and both polymorphs of 4 display layers in which the molecules are connected by N-H···O bonds in one and by relatively short and approximately linear C-Br···O interactions in the other dimension. Despite the alleged steric equivalence of methyl and chloro substituents (“chloro-methyl exchange rule”), the packing architecture of the methyl compound 3 is not related to any of the preceding structures. In this case, the N-H···O bonding leads to centrosymmetric cyclodimers, which pack in such a way that each methyl group is located between two oxygen atoms and above the face of an aromatic ring in a topology consistent with C-H···O and C-H···C(π) bonding. All the structures are pervaded by weak C ar -H···O hydrogen bonds; moreover, 1 displays a short C-H···F hydrogen bond and a C-F···C(π) interaction, and π-stacking of aromatic rings is observed in 1, 3 and 4B

A new silver(I) nitrate complex of 2-(2-aminoethyl)pyridine (aepy), [Ag 2 (μ-NO 3 ) 2 (μ-aepy) 2 ] n , has been synthesized and characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffractometry. Two silver(I) ions are doubly bridged by two bidentate aepy ligands forming dimeric building block [Ag 2 (μ-aepy) 2 ] units with a Ag···Ag distance of 3.0587(17)Å . These dimeric units are further doubly bridged by two nitrato ligands into a one-dimensional polymeric chain. The nitrato ligand exhibits an uncommon bidentate bridging mode of Ag-ONO-Ag. The title complex features a hydrogen bonded two-dimensional supramolecular framework formed via N-H···O hydrogen bonds, involving the uncoordinated O atom of the nitrate ligand and amine hydrogen atoms of aepy. The thermal stability of the title complex was investigated using thermogravimetry and differential thermal analysis.

A Cu(II) complex of the amino acid L-selenomethionine of stoichiometry Cu(L-SeMet) 2 , has been prepared and characterized. Crystallographic data were obtained by means of X-ray powder diffractometry and showed that the compound is isostructural with the related complex of L-methionine, Cu(L-Met) 2 . The structural analogy is also supported by the analysis of the IR and Raman spectra of the complex, which are briefly discussed in comparison with those of free L-selenomethionine.

The reaction of the aliphatic unsymmetrical tripod [N(CH 2 CH 2 NH 2 ) 2 (CH 2 CH 2 OH)], H 5 -1, with cobalt(II) chloride in THF yields after aerial oxidation the dinuclear complex [(H 4 -1)Co III (μ-OH)Co III (H 4 -1)](Co II Cl 4 )Cl, [5](CoCl 4 )Cl. The trianion 5 3− contains two cobalt atoms triply bridged by two alkoxo groups of the singly deprotonated ligand (H 4 -1) − and a hydroxo group. The new ligand [N(CH 2 CH 2 CH 2 NH 2 )(CH 2 CH 2 OH) 2 ], H 4 -3, providing an N 2 O 2 donor set reacts with cobalt(II) chloride to give after aerial oxidation the hexanuclear complex [Co III 4 (H 2 -3) 4 Co II 2 (HOMe) 2 Cl 2 (μ-OH) 4 ], [6]Cl 2 , containing an unprecedented mixed-valent Co III 4 Co II 2 core.

The 2-pyrrolidino-1,3-dienes (E)-5 and (Z)-5 are obtained by the reaction of lithium di(tertbutyl) cuprate with propyne iminium salt 3. Quantitative Z→E isomerization of 5 takes place within 4 hours at 20 °C. In benzene solution, (E)-5 slowly equilibrates with a [1,5]-H shift to form the 1-amino-1,3-diene derivative 6. In concentrated chloroform solution, however, (E)-5 is transformed into the 3-pyrrolidino-bicyclo[4.2.0]octa-2,4-diene 7 which is identified by X-ray crystal structure analysis. A mechanism for this transformation is proposed.

Structural examination of the metabolic pool of the aerial parts of Pelargonium sidoides DC has led to the isolation of two new metabolites, 4-allyl-2,5-dimethoxyphenol-1-β -D-glucopyranoside and 6,7-dihydroxycoumarin-8-sulfate, along with a series of uncommon compounds including (2R,3R)-(+)-dihydroquercetin-3-β -glucopyranoside, (2R,3R)-(+)-dihydrokaempferol-3-β - glucopyranoside, fraxetin-7-β -glucopyranoside, 7-methoxycoumarin-6-β -glucopyranoside, umckalin, orientin-2”-gallate, and isoorientin-2”-gallate. They are accompanied by the widespread isoorientin, orientin, fraxetin, (2R,3S)-epigallocatechin-3-gallate, gallic acid and protocatechuic acid. The structures of the compounds were established from spectroscopic studies. Determination of configurations was achieved by circular dichroism.

On nucleophilic substitution with S-nucleophiles at room temperature, 1-(4-dimethylamino)- [2,3,5,6-tetrachloropyridin-4-yl]pyridinium chloride (2) yielded tetrachloro-4-sulfanylpyridines and 2,3,5-trichloro-4,6-disulfanylpyridines depending on the reaction conditions. Similarly, the tricationic (3,5-dichloropyridine-2,4,6-triyl)-1,1’,1”-tris[4-(dimethylamino)pyridinium] trichloride 3 was reacted with S-nucleophiles to give the corresponding 3,5-trichloro-2,4,6-trisulfanylpyridines under mild conditions.

The β -amino-hydroxylamines 5a - d are prepared of the α-amino-oximes 1a - d with boranedimethylsulfide. With mercury-EDTA, 5a - d react to (E/Z)-oxime-lactams 3a - d and benzaldoxime 7. Additionally 5b,c give the bicyclic amidine-N-oxides 8b,c, which slowly hydrolyze to the hydroxylamine-lactams 9b,c. These are easily oxidized to (E/Z)-3b,c. Postulated as intermediates in the mercury-assisted reduction of 5, the cyclic hydroxylamines 10a - d are available from the nitrones 4a - d with LiAlH 4 . From 10a - d with mercury-EDTA the same products are obtained as from 5a - d but without 7. Only the pyrrolidine 10a forms besides (E/Z)-3a the nitrone 4a. Thinlayer chromatography shows that the pure isomers of 3a - d in solution isomerize, contrary to the amine-oximes 1a - d. The configuration of the oxime-lactams depends on the manner of preparation. With mercury-EDTA, 1b,c yield 3b,c with retention of the configuration, while the oximation of phenacyl-lactams 13b,c give rise to (E/Z)-mixtures of 3b,c. The condensed imidazoles 12 result from the nitrones 4a - d and the dihydrooxadiazines 2a,d on treatment with hydrogen chloride.

NaNiO 2 was prepared through oxidation of a Na 2 NiO 2 / NiO mixture (1:1) in dried oxygen at 500 °C. Single crystals have been grown by annealing of NaNiO2 powder at 600 °C for 83 d in a flow of dried oxygen. According to the X-ray analysis of the crystal structure (C2/m, Z = 2, a = 5.3177(2), b = 2.8458(1), c = 5.5819(3) Å , β = 110.409(2)°, R 1 (all) = 3.4%, 185 independent reflections), the Jahn-Teller distorted NiO 6 octahedra, sharing edges, build up layers lying parallel to the ab plane. A phase transition (associated with an energy of 2.9 kJ/mole) to a high temperature rhombohedral form (R3̅m, Z = 3, a = 2.958(1), c = 15.748(2) Å , at 300 °C) was observed by Guinier and DSC measurements at 195 °C. The magnetic susceptibility of the monoclinic phase can be described by the Curie-Weiss law between 100 and 330 K: μ = 2.01μB (g = 2.32), Θ = 37 K, indicating the dominance of ferromagnetic interactions of S = 1 / 2 spins within the NiO 2 layers. Antiferromagnetic interlayer interactions produce an overall antiferromagnetically ordered structure below 18 K.