Volume 47, Issue 10

By photochemical reaction of Cs 2 [B 6 H 6 ] with KNO 2 in aqueous alkaline solution the mononitritohydrohexaborate Cs 2 [B 6 H 5 (ONO)] and the dinitrohydrohexaborate trans-Cs 2 [B 6 H 4 (NO 2 ) 2 ] are formed. The pure compounds have been separated by ion exchange chromatography on diethylaminoethyl cellulose. Their structures are proved by 11B NMR spectra which show the features of substituted B 6 cages with C 4v and D 4h point symmetry. Due to the +M effect of the nitrito group in contrast to the — M effect of the nitro substituents characteristic 11 B chemical shifts of opposite sign have been observed. Furthermore, the O or N coordination is distinguishable by different vibration modes within the substituents.

The compounds Mg 2 Ni 3 P and Mg 2 Ni 3 As were prepared by heating the elements. Their structures have been determined from single-crystal X-ray data. The structure of the phosphide is a rhombohedral ternary variant of the cubic Laves structure type MgCu 2 (R 3̄ m; hexagonal lattice constants: a = 4.971(0) Å, c = 10.961(2) Å). The ordered substitution of one quarter of the metal atoms by phosphorus and the resulting shorter distances are responsible for the rhombohedral symmetry. The arsenide crystallizes in the MgCu 2 type structure (Fd 3 m; a = 6.891(1)A, composition Mg 2 Ni 3 As) with a statistic distribution of the Ni and As atoms; the relevant homogeneity range extends from Mg 2 Ni 2.9 As 1.1 to Mg 2 Ni 3.5 As 0.5 .

The complexes t C 4 H 9 N=VCp(NH t C 4 H 9 )[E(SiMe 3 ) 3 ] (E = Si, Ge, Sn), t C 4 H 9 N=VCp(NH t C 4 H 9 )(EPh 3 ) (E = Sn, Pb), t C 4 H 9 N=VCp(O t C 4 H 9 )[E(SiMe 3 )3] (E = Si, Ge) and t C 4 H 9 N=VCp(O t C 4 H 9 (SnPh 3 ) have been prepared by reaction of chlorovanadium(V) compounds with LiER 3 (R=SiMe 3 , Ph). All complexes were characterized by NMR spectroscopy ( 1 H, 51 V), the stannyl complex 5 by X-ray diffraction analysis. The syntheses of t C 4 H 9 N=VCp(O t C 4 H 9 )(C 6 H 5 ) and LiSn(SiMe 3 ) 3 · 3 THF are also described.

Pale yellow crystals of LiBa 4 [Mo 2 N 7 ] • BaCl 2 (monoclinic, P2 1 /m; a = 1113.5(3), b = 605.8(1), c = 1122.7(3) pm; β = 95.65(2)°; Z = 2) were grown from the melt (LiCl/Ba 3 [MoN 4 ], molar ratio 3:1, T max = 1050 °C) by cooling (5°C/h). The crystal structure contains dimeric units [Mo 2 N 7 ] 9- (eclipsed conformation; N-Mo-N: 173.7°; Mo-N (term.) : 182.7(5)-186.1(8) pm; Mo-N (bridg.) : 190.6(8) and 192.3(8) pm).

The synthesis and crystal structure of 1,3-di-tert-butyl-4,4-dimethyl-2-pentafluorophenyl-1,3,4,2-diazastannoboracyclobutane are reported.

The zwitterionic λ 5 -spirosilicates bis[1,2-benzenediolato(2–)][2-(dimethylammonio)-phenyl]silicate (4) and bis [2,3-naphthalenediolato(2–)][2-(dimethylammonio)phenyl]silicate (5; isolated as 5 · ½CH 3 CN) were synthesized and the crystal structure of 4 was studied by X-ray diffraction. 4 was prepared by reaction of [2-(dimethylamino)phenyl]trimethoxysilane (7) or bis[2-(dimethylamino)phenyl]dimethoxysilane (8) with 1,2-dihydroxybenzene in acetonitrile at room temperature. 5 was synthesized analogously by reaction of 7 or 8 with 2,3-dihydroxynaphthalene. The silanes 7 and 8 were obtained by reaction of tetramethoxysilane (6) with [2-(dimethylamino)phenyl]lithium. The reactions 8 → 4 and 8 → 5 involve a remarkable Si–C cleavage leading to the formation of (dimethylamino)benzene. The pentacoordinate silicon atoms of 4 and 5 are surrounded by four oxygen atoms and one sp 2 hybridized carbon atom. The coordination polyhedron of 4 can be described as a distorted square pyramid, the carbon atom being in the apical position (the structure is distorted by 69,1 % from the trigonal bipyramid towards the square pyramid). In the crystal, 4 forms an intramolecular N-H···O hydrogen bond.

The amino-substituted vinylchlorosilanes 4-7 are synthesized from N,N,N′-trimethylethylenediamine (8a) or tris(trimethylsilyl)ethylenediamine (8b), Li Bu n and organodichlorovinylsilanes. 5 eliminates trimethylchlorosilane when distilled and yields 1,3-diaza-2-silacyclopentane 9, whereas the compounds 6 and 7 show a great tendency to oligomerize. The reaction of 4 with LiBu t gives a neopentylsilene intermediate 10 a which can be trapped by isoprene or 1,3-butadiene yielding small amounts of the Diels-Alder products 11 and 12, respectively. The main reaction pathway for 10 a is rearrangement with migration of a Me 3 Sigroup from nitrogen to the silene’s carbon atom and a new N—Si bond formation to give the diazasilacyclopentane 10 which has been characterized by X-ray diffraction analysis. This intramolecular rearrangement appears to involve a pentacoordinated silene Si-atom. No dimerisation of 10a to a disilacyclobutane is observed. The introduction of a second Si-tris(trimethylsilyl)ethylenediamine substituent at the SiC frame work does not result in silene stabilisation: there is no evidence for Si-hexacoordination in silene 15 nor in the [4+2] cyclo-addition product with isoprene (14).

(PPh 4 ) 2 [TiCl 3 (NSiMe 3 )] 2 · CH 3 CN has been prepared from [TiCl 2 NSiMe 3 )] ∞ with PPh 4 Cl in acetonitrile solution as yellow crystals. The compound crystallizes in the triclinic space group P T with one formula unit per unit cell, 3447 observed unique reflections, R = 0.053. Lattice dimensions at 200 K: a = 1030(1), b = 1253(1), c = 1374(1) pm, α = 77.46(8)°, β = 73.93(8)°, γ = 69.99(9)°. The structure consists of PPh 4 + ions and centrosymmetric dimeric anions [TiCl 3 (NSiMe 3 )] 2 2- , in which pentacoordinate titanium atoms are associated via the nitrogen atoms of the silylimido groups. (PPh 4 ) 2 [TiCl 4 (OSPCl 2 )] 2 has been prepared by the reaction of PPh [OSPCl 2 ] with titanium tetrachloride in CH 2 C1 2 solution as orange crystals. (Space group P1̄, Ζ = 1, 3242 observed unique reflections, R = 0.033). Lattice dimensions at 193 K: a = 1114.8(2), b = 1190.6(2), c = 1218.7(2) pm, α = 72.18(1)°, β = 85.45(1)°, γ = 69.19(1)°. The structure consists of PPh 4 + ions and centrosymmetric dimeric anions [TiCl 4 (OSPCl 2 )] 2 2- , in which hexacoordinate titanium atoms are associated via two chlorine atoms. The OSPCl 2 - group is coordinated via the oxygen atom.

Methylation of epindolidione gives the Ν,N′-dimethyl derivative which was characterized by X-ray diffraction. Dibenzo[b,g][1,5]naphthyridin-6,12(5,11 H)-dione (Epindolidione) [1] sind Strukturisomere des Indigos. Die geringe Löslichkeit sowie - ähnlich wie in Indigo [2] - die tiefe Lage der NH-und CO-Valenzschwingungen von Epindolidion ist auf intermolekulare Wasserstoffbrücken zurückzuführen. Obwohl Epindolidion nur gelb ist, wurde die Verbindung von Lüttke und Klessinger als indigoider Farbstoff eingestuft [3]. In letzter Zeit fanden Epindolidione als potentielle Halbleiter [4] sowie für den Einbau in Peptide Beachtung [5]. Im Rahmen von Arbeiten über Naphthyridin-Derivate [6] sowie über Metallkomplexe von Farbstoffen [7] interessierte die Alkylierung bzw. Metallierung (Isolobal-Analogie [8]) von Epindolidion, die am N- oder (und) O-Atom erfolgen kann.

z1.5 Time-consuming 13 C NMR measurements of sparingly soluble ring-substituted cyclopentadienyl metal complexes can be avoided if INEPT techniques are applied. In particular, polarization transfer based on long range 13 C— 1 H couplings ( n J( 13 C 1 H); n = 2, 3) can be used to observe 13 C NMR signals of quaternary 13 C nuclei, which are difficult to observe in normal 13 C NMR spectra. The improvement in the signal-to-noise ratio enabled to observe satellites due to 77 Se- 13 C and 125 Te —13 C couplings. Some typical ferrocene derivatives as well as η 5 -cyclopentadienyl-manganese- and -rhenium tricarbonyl derivatives were selected to demonstrate that the recommended methods are independent of the metal and of the type of ring substitution.

Quinonylmethylenaminones 5 and 6 are synthesized and cyclized to spiro compounds 7 and 8. Quinonylpropylenaminone 15 is made in the same way. Cyclization in acetic acid yields quinolines 11 and 12, in trifluoroacetic acid/trifluoroacetic anhydrid diacylenamine 16 is obtained. The product of 15 in perchloric acid is benzazocine 20. The structure of 20 is proven by X-ray analysis. The course of the reaction is discussed.

[Ni(′N 2 H 2 S 2 ′)], 1, forms from Ni(II) salts and the tetradentate thiolate-amine ligand ′N 2 H 2 S 2 ′2- (= 1,2-ethanediamine-N,N′-bis(2-benzenethiolate)(2-)) [2], or by reduction of the Schiff base complex [Ni(gma)] (gma 2- = glyoxal-bis(2-mercaptoanilide(2–))) with NaBH 4 . Bases easily deprotonate 1 to yield the [Ni(′N 2 S 2 ′)] 2- dianion, which is extremely easily oxidized to give the Ni(II) monoanion [Ni(′N 2 S 2 ′)] - which was isolated as [AsPh 4 ][Ni(′N 2 S 2 ′)], 4, and characterized by X-ray structure analysis. 4 contains a distorted square planar NiN 2 S 2 core, in which two thiolate-S and two amido-N donors are surrounding the nickel atom. Deprotonation of 1 was further substantiated by H*/D + exchange to give [Ni(′N 2 D 2 S 2 ′)] and by alkylation. Consecutive reaction of 1 with n-BuLi and CH 3 I leads to fourfold methylation of 1 yielding [Ni(′N 2 Me 2 S 2 Me 2 ′)I 2 ], 8, while alkylation of 1 by CH 3 I in the absence of base yields [Ni(′N 2 H 2 S 2 Me 2 ′)I 2 ], 5, in which only the thiolate donors have been alkylated. X-ray structure analysis shows 8 to contain a distorted octahedral NiN 2 S 2 I 2 core with two sulfur atoms occupying axial trans positions and two nitrogen and two iodine atoms occupying equatorial cis positions. 1 also forms by reaction of [Ni(CO) 4 ] with ′N 2 H 2 S 2 ′-H 2 , which is explained by a series of oxidative addition and reductive elimination reactions. Palladium and platinum homologues [Pd(′N 2 H 2 S 2 ′)], 9 and [Pt(′N 2 H 2 S 2 ′)], 10, were synthesized from [MC1 2 (COD)] (M = Pd, Pt) and ′N 2 H 2 S 2 ′-H 2 , and exhibit analogous reactivity as 1.

We have developed a chemical-enzymatic synthetic approach to gonadotropin releasing hormone Glp 1 –His- 2 –Trp 3 –Ser 4 –Tyr 5 –Gly 6 –Leu 7 –Arg 8 —Pro 9 –Gly 10 –NH 2 (GnRH) which enables one to perform the synthesis efficiently according to minimal protection strategy with all reactive side chains of amino acids unprotected. Five peptide bonds His 2 –Trp 3 , Tyr 5 –Gly 6 , Leu 7 –Arg 8 and Trp 3 –Ser 4 , Ser 4 –Tyr 5 were formed by means of a-chymotrypsin and papain, respectively. The remaining four bonds Glp 1 –His 2 , Gly 6 –Leu 7 , Arg 8 —Pro 9 , Pro 9 —Gly 10 were formed by chemical methods. The synthesis is simple to carry out and there are no problems in scaling up as demonstrated by the final coupling on 2 g scale affording highly pure GnRH in the yield of 84-90%.

The photodegradation of 2-(2-Furyl)-benzimidazole (Fuberidazole 1) has been reinvestigated employing advanced HPLC—UV/VIS technique and fluorescence emission and excitation spectroscopy in methanol at natural pH, in acidic medium and in aqueous solutions at pH 7 and 3, and four main products benzimidazole-2-carboxylic acid 3, its methyl ester 2, 1-methoxy benzimidazole 5, methyl 4-oxo-2-benzimidazole crotonate 7 (cis and trans isomers) besides benzimidazole 4 and 2,2′-bibenzimidazole 6 and other side products have been isolated and characterized. The kinetics of the photodegradation process was followed independently by HPLC—UV and fluorescence emission showing a significant similarity of the curve habit; this allows to monitor a photodegradation at very low concentrations (5·10 -5 -5·10 -6 Μ). The quantum yield of disappearance of Fuberidazole has been determined.

Arylidene malononitrile reacted with cyanothioacetamide under basic condition to afford the pyridine derivative (2). The same product was obtained from the reaction of arylidene ethylcyanoacetate, arylidene diethyl malonate, arylidene pyrazolinone with cyanothioacetamide under the same condition. A resonable mechanism for this behaviour was suggested.

Bis(thiodibenzoylmethanato)-nitridotechnetium(V) and -rhenium(V) as well as bis(1-phenyl-3-methyl-4-benzoyl-pyrazol-5-thionato)-nitridorhenium(V) have been prepared by the reaction of NBu 4 [TcNCl 4 or ReNCl 2 (PPh 3 ) 2 with the ligands. The dark brown complexes were characterized by elemental analysis, UV/VIS spectrometry and FAB mass spectra.

From leaves and bulbs of Ornithogalum nutans L. (2 n = 28), seventeen cardenolides were isolated by column chromatography, DCCC and TLC. The structure elucidation was performed by means of 1 H NMR, 13 C NMR, HH-Cosy, HC-Cosy and FAB-MS studies and identification of the sugar moieties by GLC after acid hydrolysis of the cardenolides. Sugar compounds were identified as digitoxose, 3-acetyl-digitoxose, 2-deoxy-allose, 6-deoxy-allose, rhamnose, xylose and apiose. Glycosides of 7β,15β, 16 α-trihydroxy-uzarigenin, 8β,16 α-dihy-droxy, 15-oxo-uzarigenin, 3 β, 11β-dihydroxy, 12-oxo, 18-nor-5 α-card-13-enolid, 11 α-hydroxygitoxigenin, 12-oxo,8, 14β-epoxy-uzarigenin, 8β-hydroxy, 15-oxo-uzarigenin and 12β-hydroxy-oleandrigenin are described for the first time, the presence of oleandrigenin-glycosides in the genus Ornithogalum was not known until now. Ornithogalum nutans L. shows a different cardenolide pattern from the second European species of the section Myogalum (LINK) PETERM. - Ornithogalum boucheanum (KUNTH) ASCHERS.

From bulbs of Ornithogalum nutans L. (2 n = 30) nineteen cardenolides were isolated by column chromatography and TLC. Thirteen substances were structurally elucidated as glycosides of Strophanthidin, Sarmentosigenin, Sarmentogenin, Bipindogenin, 2a-Hydroxy-bipin-dogenin, Syriogenin, 7a-Hydroxy,12-oxo,8β,14β-epoxy-uzarigenin, 3β,11β-Dihydroxy,12-oxo, 18-nor-5 α-card-13-enolide, 3β, 11β-Dihydroxy, 12-oxo, 18-nor-5 α-carda-13,20(22)-dienolide, mainly by means of 1 H, 13 C NMR spectroscopy, FAB-MS and identification of the sugar moieties by GLC after acid hydrolysis of the cardenolides. Six of these glycosides were identified by cochromatography (HPLC and TLC) with authentic samples. The results obtained were discussed with regard to the close botanical relationship of Ornithogalum nutans L. and Ornithogalum boucheanum (KUNTH) ASCHERS.

The new carboxylato-dinitrosyl-molybdenum complexes of the formula: [Mo(NO) 2 (O 2 CMe)2] • MeOH, Na 2 [Mo(NO) 2 (O 2 CMe) 4 ] and Mo(NO) 2 (O 2 CPh) 2 have been synthesized. Their structure was resolved on the basis of spectroscopic investigations ( 1 H NMR, IR, UV-VIS). Catalytic activity of these complexes in olefin metathesis reaction was also examined. The electronic structure of dinitrosyl-molybdenum complexes with ligands coordinating by oxygen atoms was calculated for the example of the di- and tetra-acetato-dinitrosyl-molybdenum complexes using the Fenske-Hall and INDO methods. To interpret the spectroscopic properties (UV-VIS) within the method of interaction configuration, the electronic structure of the excited states was calculated.

The red-pigmented caribbean sponge Thorecta horridus contains thorexanthin (3-methoxy-β-X-caroten-4-one) as a new carotenoid pigment. Its structure was determined by spectroscopic methods, including 2 D NMR experiments.

Full ab initio 3-21 G optimization of molecular structures of twelve planar formamidines substituted by X in Ε-configuration at imino nitrogen (N 2 ) (X = H, CH 3 , NH 2 , C 6 H 5 , OH, F, CHO, CN, BH 2 , NO (four isomers), NO 2 (planar and perpendicular conformations), and CH 2 + ) yielded the following conclusions: (1) as was found earlier experimentally, an increase of the shorter CN 2 bond lengths is associated linearly with a decrease of the longer CN 1 bond; (2) the difference of both CN distances (Δ CN) is related linearly to the Mulliken π-electron charge density at amino nitrogen (N 1 ); (3) a decrease of Mulliken π-charge density (Δ q π ) at N 1 is linearly related to a corresponding increase of Δ q π at N 2 . The scatter and a slope of –0.54 indicate a mixed mechanism of interaction between NH 2 and the substituents at amino nitrogen composed of n-π-conjugation and through conjugation; (4) an increase of σ-charge density at H 2 is correlated with an increase of N 1 – H 2 bond lengths. As a result of interaction between the lone pair at N 2 and the cis-bond of the nitro substituent this bond is calculated to be significantly shorter than the other one by 0.042 A. The same effect is calculated for the E-isomer of C-nitro substituted formamidine (Δ = 0.037 A) in contrast to the corresponding Z-isomer (Δ = 0.004 Å). A selection of experimental X-ray determinations of nitro-substituted compounds confirm this effect.

The edge sharing bioctahedral anions [M 2 Br10] 2- , M = Os, Re, have been prepared from [MBr 6 ] 2 in trifluoroacetic acid containing Hg 2+ ions at room temperature. Heating the solid decabromodirhenate(IV) with Hg in a vacuum at 100 °C affords the octabromodirhenate(III) with a quadruple bond between the Re atoms in quantitative yields.