Volume 48, Issue 4

Colourless monoclinic (space group C2/m) single crystals up to 1 mm long of K 2 [SeMo 3 O, 3 ] · 3.5 H 2 O and K 2 [SMo 3 O 13 ] · 4 H 2 O, respectively, were prepared from aqueous solution. Crystal data: Se compound a = 1703.5(2), b = 1088.5(1), c = 865.3(1) pm, β = 109.666(9)°, 1670 unique reflections, 123 parameters, R g = 0.0233; S compound a = 1702.7(2), b = 1079.6(1), c = 884.9(1) pm, β = 112.248(9)°, 1458 unique reflections, 123 parameters, R g = 0.0250. Both compounds cleave very easily to thin fibres. The chain-like heteropoly-anions are composed of chains of edge-sharing MoO 6 coordination octahedra and XO 4 tetrahedra (X = S, Se) linked to three different octahedra through common corners. Differential thermal analysis indicates that no decomposition occurs with K 2 [SMo 3 O 13 ] · 4 H 2 O except removal of water of crystallization up to 500°C. Decomposition to various potassium molybdates takes place between 460 and 470°C with the Se compound.

Colourless triclinic single crystals of Na 6 [TeMo 6 O 24 ] · 22 H 2 O were grown from aqueous solution (space group P 1, a = 1030.89(9), b = 1056.7(1), c = 1106.32(9) pm, α = 90.120(7), β = 115.220(6), γ = 105.195(7), Ζ = 1, 295 Κ, 336 parameters, 3181 reflections, R g = 0.0186). There are three crystallographically independent Na + cations. Two of them are coordinated octahedrally by water molecules only. The third Na + cation is bound to five H 2 O and one oxygen atom (O(4)) belonging to the Anderson-Evans type anion [TeMo 6 O 24 ] 6- . The sodium-centered coordination octahedra are linked by common edges exclusively formed by water molecules to yield chain-like polycations {Na 3 (H 2 O) 11 } n ,3n+ which are bound by the Na(1)-O(4) contact to the anions situated on crystallographic centers of inversion forming a layer-like arrangement. Further connections between the polycations and the [TeMo 6 O 24 ] 6- anions are established by hydrogen bonds involving all the oxygen atoms of the anion except O(4) as almost equivalent proton acceptors regardless of their bonding mode to Te or Mo.

Mixed complexes of Co(III) with 2-oximinopropionic (H 2 A) or 2-oximino-3-phenylpropionic (H 2 B) acid and different amine (imidazole, benzimidazole, pyridine, β-picoline, γ-picoline) are reported. Characterization of the complexes was based upon elemental analysis, conductivity and JR, 1 H NMR, and electronic absorption spectra, and X-ray diffraction analysis. The organic ligands behave as O,N donors via the carboxyl oxygen and the oxime nitrogen atoms. A trans-octahedral structure has been assigned to the bis(2-oximinocarboxylato)bis(amine)cobalt(III) on the basis of 1 H NMR data. The crystal and molecular structures of the complexes trans-[bis(2-oximinopropionato)bis-(imidazole)]- (I) and trans-[bis(2-oximinopropionato)bis(pyridine)]cobalt(III) (II) were determined. I crystallizes in space group P2/n with a = 14.1 67(2), b = 8.774(1), c = 14.785(2) Å,β = 113.37(1)°, Z = 4, D calc = 1.568 g · cm -3 . II crystallizes in space group P1̄ with a = 9.122(2), b = 10.038(2), c = 11.759(2) Å, α = 69.95(1)°, β = 67.47(2)°, γ = 69.49(2)°, Ζ = 2, D calc = 1.547 g cm -3 . The structures were refined to unweighted R factors of 0.036 and 0.028, respectively. The coordination sphere around Co is pseudo-octahedral with the 2-oximinopropionato ligands occupying four equatorial positions, and the amines in axial positions.

N,N′-Bis(salicylidene)ethylenediaminatocobalt(III) hydroxide is treated with chloroform in methanol to yield the corresponding chloride in pure, crystalline form. Results of the crystal structure determination compare well with those in earlier reports of dimeric [Co(salen)Cl] 2 units and incorporated CHCl 3 molecules. Electrochemical experiments in DMF and pyridine show that the chloride fully dissociates in these donor solvents. Thus, the quasireversible oneelectron reduction to Co(salen) is observed in cyclic voltammograms.

Whereas (COD)PtCl 2 usually reacts with bidentate phosphine ligands under substitution of the COD ligand, the reaction with the newly synthesized 1,4-bis-[di(t-butylphosphino)] butane results in the insertion of COD into one Pt-P bond affording [(t-Bu) 2 P(CH 2 ) 4 P(t-Bu) 2 -(C 8 H 12 )-PtCl] + Cl - (1). 1 crystallizes in the monoclinic space group C2/c with a = 3912.8(8), b = 1765.6(3), c = 3851.3(4) pm, β = 118.36(2)°, Ζ = 24. In the cation of 1 the second C=C bond remains coordinated to the central Pt 2+ ion. The square-planar coordination of Pt 2+ ion is completed by a Cl ligand and the second P atom of the phosphine ligand. The inserted C-C bond is elongated to 149(5) pm with respect to the coordinating C=C bond of 133(6) pm.

The electrochemical oxidation of Cd in acetonitrile solution of 1-hydroxy-2-pyridinethione (HPT) and 2,2′-bipyridine (bipy) affords [Cd(PT) 2 (bipy)] · H 2 O and [Cd(PT)(bipy) 2 ]ClO 4 · 1/4(bipy). The crystal structure of the perchlorate salt shows the molecule to have a distorted octahedral CdN 4 OS skeleton.

The new compound [K(Crypt-2.2.2)] 2 I 12 has been prepared by the reaction of [K(Crypt-2.2.2)]I with iodine in a mixture of ethanol and dichloromethane. It crystallizes in the triclinic space group PĪ with a = 1201,5(5), b = 1213,4(5), c = 1432,1(2) pm, α = 69,11(2), β = 72,01(2), γ= 61,93(3) and Z = 1. The crystal structure has been refined to R F = 0.030 for 2882 reflections. The structure may be described as a layerlike packing of I 12 2- anions and [K(Crypt-2.2.2)] + cations. The anion with point symmetry C i consists of two pentaiodide groups and a bridging iodine molecule.

In the reaction of 2-chloro-1,3,5-trimethyl-4,6-dioxo-1,3,5,2 λ 3 -triazaphosphinane (1) with β-chloroethylamine hydrochloride and bis-(β-chloroethyl)amine hydrochloride, 1,3,5-trimethyl-2-(β-chloroethyl)amino-4,6-dioxo-1,3,5,2 λ 3 -triazaphosphinane (4) and 1,3,5-trimethyl-2-bis-(β-chloroethyl)amino-4,6-dioxo-1,3,5,2 λ 3 -triazaphosphinane (5) were obtained. The reaction of 4 and 5 with sulfur, hexafluoroacetone, tetrachloroorthobenzoquinone and 4-nitrobenzoyl azide gave the 1,3,5-trimethy1-4,6-dioxo-1,3,5,2 λ 4 -triazaphosphinanes 6 and 9 and the 1,3,5-trimethyl-4,6-dioxo-1,3,5,2 λ 5 -triazaphosphinanes 7 and 8. The characterization of 4-9 rests, especially, on their 1 H, 13 C and 31 P NMR spectra, mass spectra and X-ray structure determinations of 4 and 5.

The metallic grey compound Na 2 [SnAs 2 ] was prepared from a molten mixture of the elements. Na 2 [SnAs 2 ] crystallizes in the tetragonal space group I4 1 /acd, Z = 32, with the lattice constants: a = 1416.6(3) pm, c = 2119.1(4) pm, c/a = 1.4959. In the crystal structure four [SnAs 4 ] tetrahedra are connected by common corners forming adamantan analogous [Sn 4 As 10 ] units. The further connection of these tetrameric moieties by the terminal As atoms results in a three-dimensional framework ∞ 3 [SnAs 2 2- ], in which the Na atoms occupy distorted tetrahedral and octahedral holes.

Phase transfer catalytic isopropylation or tert-butylation of cyclopentadiene yields 1-6 in efficient one-pot procedures. Powdered potassium hydroxide or solid sodium hydride are the prefered bases, Aliquat 336 or dibenzo-18-crown-6 are the PT catalysts.

As described by many authors, covalently linked dye-electron accepting group systems may provide a very efficient intramolecular fluorescence quenching and electron transfer. Due to the very fast thermal back reaction, no stable charge separation can be achieved. In contrast, J-aggregates of cyanine dyes (1,1′-diethyl-2,2′-cyanine iodide = 1) containing some molecules with covalently linked viologen groups (1-[3-[2-[(1-ethyl-2(1 H)-chinolinyliden)methyl]-chinolinium-l-yl]propyl]-1′-methyl-4,4′-bipyridinium triiodide = 2, 1,1′-(4,4′-bipyridinium-1,1′-diyldi-5,1 -pentandiyl)bis[2-[(1-ethyl-2(1H)-chinolinyliden)methyl]chinolinium] tetrachloride = 3) show an increase in charge separation. Hydrogen production experiments in these organized assemblies, both via inter- (with methyl viologen) and intramolecular (with 2 or 3) charge separation were successful. Hydrogen production experiments based on intramolecular charge separation gave even higher quantum yields than via intermolecular reaction steps. In contrast, hydrogen production experiments with dilute aqueous solutions (no aggregates) with 2 or 3 failed in the absence of methyl viologen (MV 2+ ) due to the fast intramolecular back reaction. In the presence of MV 2+ compounds 1-3 were able to produce H 2 only when irradiated with near UV-light (λ > 280 nm). Irradiation of these solutions with visible light (λ > 400 nm) resulted in no H 2 production. This is attributed to competing nonradiative desactivation processes. Dilute aqueous solutions of 1-3 gave also no visible emission (λ > 400 nm) in the absence of (additional) quenching molecules. So a further progress was achieved by using the J-aggregates: competing nonradiative desactivation processes (of the excited dye molecules) were diminished in J-aggregates.

A method is described which allows the titrimetric determination of the pH of decomplexation and of the formation constant of chelating ion-exchangers, although the titration curve is not complete. Iterative linearization leads to the formation constants and allows the completion of the titration curves. The studied systems are of the type MeL and MeL 2 , where the metals Me are zinc, copper and manganese, and the ligand L is Eriochrome Black T. The method may also be used for the determination of the number of ligands in a complex of the type MeL n .

13 C NMR and UV spectroscopy of aqueous phloroglucinol over the pH range 2.6 to 15 confirms that the dianion exists predominantly as the keto form (3,5-dihydroxy-2,5-cyclohexadienone dianion 2c, δ(>CH 2 ) = 46 ppm, δ(≥CH) = 101 ppm, δ(C 3 ,C 5 ) = 188 ppm, δ(C 1 ) = 197 ppm). All other states of ionization, i.e. neutral la (δ(>CH) = 98 ppm, δ(5(C 1 ,C 3 ,C 5 ) = 160.9 ppm), monoanion 1b (δ(>CH) = 98 ppm, δ(C 1 ,C 3 ,C 5 ) = 164.4 ppm) and trianion 1d (δ(>CH) = 100 ppm, δ(C 1 ,C 3 ,C 5 ) = 170 ppm) exist predominantly as the benzene forms. There is some evidence, consisting of a broadening of the signals from the 3,5-dihydroxy-2,5-cyclohexadienone dianion 2c in the pH range from ∾ 9 where they start to appear, to ∾10 where they approach their maximum values, for a small but noticeable equilibrium concentration of the cyclohexen-1-ol-3,5-dione (monoanion) 3b or the 3,5-dihydroxy-2,5-cyclohexadienone (monoanion) 2b forms. Other keto forms have not been detected. The third pK a turns out to be close to 14.

It is shown (1) that in most reactions of anilines 2 with 1-sulfonyl-2,2-dimethylaziridines 1 both isomeric products 3 and 4 are formed, (2) that the “normal” product 4 obtained by attack on position 3 of 1 usually arises in a small or negligible amount that seems to decrease with decreasing basicity of 2, and (3) that the amount of 4 strongly increases with increasing steric demand of 2. Formation of 4 is explained by a lag of bond making in S N 2.

Two linear dihydroxy diterpenes were isolated from the sponge Myrmekioderma styx. The structure of these com pounds were deduced by MS, UV, IR , 1 H and 13 C NMR , 1 H - 1 H COSY , XHCORR , and COLOC experiments. Both com pounds 5 and 6 are toxic toward Artemia salina; compound 5 showed inflammatory activity, by histamine release.

Derivatives of (diphenylmethylene-amino) acetic acid 1-3 react in the presence of bases (NaH, t-BuONa) or under phase transfer conditions with carbon disulfide to give the corresponding ketene dithioacetals 4-11 after alkylation. Phenyl isothiocyanate and dicyclohexyl carbodiimide give rise to ketene-S,N- and N,N-acetals. Methyl 2-(diphenylmethyleneamino)-2-(1,3-dithiane-2-ylidene) acetate (7) was characterized by an X-ray structure determination. The compound has a 2-aza-1,3-butadiene fragment containing two well localized double bonds. The C=N-C=C group is significantly non-planar, the relevant torsion angle amounts to -103.5(3)°.

A novel dihydroxy-substituted aminoxyl spin label, 4-hydroxy-3-(3'-hydroxypropyl)-2,2,6,6-tetramethylpiperidine-1-oxy (5), has been prepared. From this aminoxyl radical, a spin-labeled crown ether, 16,16,18,18-tetramethyl-2,5,8,11-tetraoxa-17-azabicyclo[ 13,4,0]-nonadecane-17-oxy (12), and a spin-labeled cyclic diester, 16,16,18,18-tetramethyl-3,10-dioxo-2,5,8,11-tetraoxa-17-azabicyclo[13,4,o]nonadecane-17-oxy (13), have been acquired. Other four new stable aminoxyl radicals 8,9,10, and 11 have also been obtained within the synthetic approach. It has been demonstrated that the cyclic ether compound (7) is generated by the reduction of its corresponding lactone which is sidely derived from the oxo-reduced species of 3 by intramolecular cyclization.

The protein biotinylating agent, pentafluorophenyl 6-(biotinylam ido)hexanoate (3) was synthesized. A straightforward synthetic route, biotin, biotin pentafluorophenyl ester (1), 6-(biotinylam ido)hexanoate (2) and pentafluorophenyl 6-(biotinylam ido)hexanoate (3) was followed. This agent was used for biotin-labelling of different proteins, bovine serum album in, immunoglobulin, horseradish peroxidase and β-galactosidase. Optimal conditions for the labelling were determined, as well as the influence of biotin-tagging to the biological activity of the proteins. An optimal ratio of the biotinylating agent to protein resulted in effective biotinylation without a significant decrease in the activity of the labelled enzyme. The labelled proteins proved to be suitable for immunodetection of proteins in both microplate and Western blot immunohistochemistry, as well as in a competitive steroid ELISA of testosterone and 20-hydroxyecdysone.

Synthesis of 4-cyanofuro(2,3-b)quinolines starting from 2-chloro-4-cyano-3-vinylquinolines is described.

The longest wavelength VIS absorptions of the deeply colored CF 3 CO,H solutions of the 4,4′-chalcogenobis-(triphenylmethylium) ions 4 ++ , Y[C 6 H 4 C(C 6 H 5 ) 2 ] 2 (Y = O,S,Se,Te) resemble closely those of the corresponding monocationic 4-arylchalcogenotriphenylmethylium systems 5 + , ArYC 6 H 4 C(C 6 H 5 ) 2 , and not those of the structurally directly related 4,4′-bis(arylchalcogeno)triphenylmethylium ions 3 + , C 6 H 5 C(C 6 H 4 YAr) 2 . This is in striking contrast to the results obtained previously for analogous nitrogen systems, where “inverse”, 2 ++ , RN[C 6 H 4 C(C 6 H 5 ) 2 ], and “conventional” malachite green systems 1 + , (Ar 2 NC 6 H 4 ) 2 CR, yield almost indentical A max values. A rationalization of these observations can be achieved based on the assumption of largely delocalized dications 2 ++ versus more or less orthogonal “double monocationic” systems 4B ++ separated due to torsional twist. Whereas the formal push-pull systems 6 + , ArSC 6 H 4 YC 6 H 4 C(C 6 H 5 ) 2 (Y = O,S,Se) behaved practically like the corresponding standard systems 5 + , the mono- and bis-triphenylmethylio-substituted dibenzofurane, dibenzothiophene and thioxanthene derivatives 8 + , 9 ++ , 10 + and 11 ++ displayed hypsocromic shifts of their color bands relative to their noncyclic analogues which are only partly in accordance with predictions based on a simple frontier orbital Hückel model. The 1 H and 13 C NMR spectra of all these cationic species comply with their respective charges.

Chromium and molybdenum carbonyl photocatalyzed hydrosilation of 1,3-butadiene by triethylsilane yields exclusively the 1,4-adduct, cis-l-triethylsilyl-2-butene which has been fully characterized. Mechanistic possibilities for photocatalytic hydrosilation reactions have been put forward.

The reaction of [{(CO) 5 W}PhPCl 2 ] with S(SiMe 3 ) 2 leads to the formation of [{(CO) 5 WPhP} 2 S 2 ] (1). 1 crystallizes in the space group P2 1 /n. The lattice constants (at 298 K) are: a = 658.9(3), b = 2287.6(11), c = 1905.5(9) pm, β = 94.53(3)°. According to the crystal structure determination 1 contains a four-membered P 2 S 2 ring which is coordinated to two {(CO) 5 W} units.