Spin-crossover complexes in solution,II solvent effects on the high spin-low spin-equilibrium of [Fe(bzimpy)2](ClO4)2

Summary The influence of the solvent on the spin-equilibrium of [Fe(bzimpy)₂](ClO₄)₂ (bzimpy=2,6-bis(benzimidazol-2-yl)pyridine) has been investigated in several nonaqueous solvents by means of UV-Vis spectroscopy and magnetic susceptibility measurements. In methanol, a bis-tris ligation equilibrium is found. Both, the FeL ₂ ²⁺ and FeL ₃ ²⁺ species show spin-crossover behaviour in solution. Photometric and magnetic properties of the complex in various solvents are related. The spin-equilibrium of [Fe(bzimpy)₂](ClO₄)₂ shows the strongest sensitivity towards changes of the solvent that has ever been observed for spin-crossover compounds. Increase in solvent donor number (DN) from DN=14.1 (Acetonitril) to DN=19.1 (Methanol) causes a shift from _exp=4.21 (78% High-Spin (HS)) to _exp=3.0 (56% HS). In solvents with DN 30 deprotonation of the complex occurs yielding a low-spin species. The solvent effects are discussed in terms of the donor-acceptor concept.Dedicated to Professor Harry J. Emeléus with heartiest congratulations to his 90^th birthday on 22^th June 1993.     

Spin-crossover complexes in solution,I. Substitutional lability of [Fe(bzimpy)2](ClO4)2

Summary The iron(II) complexes of the nitrogen donor ligand 2,6-bis(benzimidazol-2-yl)pyridine (bzimpy) have been investigated in nonaqueous solvents using various spectrophotometric methods. Measurements in methanol at 20°C revealed thatbzimpy can act as a bi-or tridendate ligand towards iron(II) in this solvent, forming [Fe(bzimpy)]²⁺ (tridendate, logK=5.54), [Fe(bzimpy)₂]²⁺ (bistridentate, logK=4.12) and [Fe(bzimpy)₃]²⁺ (tris-bidentate, logK=3.85). The pronounced thermochromism of the compound is shown to be the result of both spin-crossover and dissociation equilibria. Furthermore, in solvents of higher donor numbers (30), partial or complete deprotonation of the complex [Fe(bzimpy)₃]²⁺ is observed. Triethylamine added stepwise to methanolic solutions causes successive deprotonation.This paper is dedicated to Professor Dr. Wolfgang Beck on the occasion of his 60th birthday with warmest personal wishes     

Convergent synthesis of 2′,3′-dideoxy-3′-mercapto nucleosides — Potential anti-HIV agents

Summary Methyl 3-benzoylthio-5-O-tert-butyldiphenylsilyl-2,3-dideoxy--D-erythro-pentofuranoside (4) and its corresponding anomer5 were synthesized in four steps from 2-deoxy-D-ribose and used as substrates for the synthesis of nucleosides by condensation with silylated thymidine and N⁶-isobutyryladenine. The nucleosides were deprotected by treatment with Bu₄NF inTHF followed by reaction with MeONa in MeOH to give 3-deoxy-3-mercaptothymidine (8), 2,3-dideoxy-3-mercaptoadenosine (15) and its corresponding anomer16. In the latter reactions it was important to use degassed solvents to minimize formation of the corresponding disulfides of purine nucleosides. Using Bu₄NF, without subsequent reaction with MeONa in the deprotection reaction, resulted in intermolecular transesterification reactions.On leave from Chemistry Department, Faculties of Science and Education, Tanta University, Tanta, Egypt     

Reactivity of pyrrole pigments,XXI: Structure and reactivity of Cu(II) and Zn(II) bilindione chelates

Summary Several Mn, Cu, and Zn chelates of etiobiliverdin-IV-, mesobiliverdin-IX, and its dimethyl ester are studied. The results show that the chemical constitution of the Cu biliverdin chelate corresponds to a formal metal oxidation state of (II) coordinated to a neutral radical of the NH trideprotonated biliverdin. The reactivity of the Cu(II) bilindione chelates in nucleophilic solvents agrees with that expected for a neutral radical structure of the ligand; in CH₃OH, they undergo oxidation towards dimethoxybilipurpurins. The magnetic behaviour of Cu(II) etiobiliverdinate-IV- in the solid state shows an intramolecular weak antiferromagnetic coupling d⁹Cu-to--radical (J=–23 cm^–1) and an intermolecular weak antiferromagnetic coupling -radical-to--radical (J=–45 cm^–1). The analogy of this magnetic behaviour to that of the cation radical of metalloporphyrins is discussed.

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Reaktivität von Pyrrolpigmenten, 21. Mitt.: Struktur und Reaktivität von Cu(II)- und Zn(II)-Chelaten von Bilindionen

Zusammenfassung Einige Mn, Cu and Zn Chelate von Etiobiliverdin-IV-, Mesobiliverdin-IX und seinem Dimethylester werden untersucht. Im Komplex koordiniert ein Metallatom (mit der Formalladung II) mit einem Neutralradikal des dreifach NH-deprotonierten Bilindions. Die Reaktivität des Komplexes gegenüber nukleophilen Lösungmitteln entspricht erwartungsgemäß dem eines neutralen -Radikals; in CH₃OH wird er zu Dimethoxybilipurpurin oxidiert. Bei Cu(II)-Etiobiliverdinat-IV beobachtet man im festen Zustand neben schwacher, antiferromagnetischer Kupplung zwischen d⁹Cu und -Radikal (J=–23 cm^–1) auch eine schwache, intermolekulare, antiferromagnetische Wechselwirkung zwischen zwei -Radikalen (J=–45 cm^–1). Dieses magnetische Verhalten wird dem des -Kationradikals von Metalloporphyrinen gegenübergestellt.

     

Diastereomeric Oxathia[n](1,1′)ferrocenophanes

Zusammenfassung Neue Oxathiaferrocenophane wurden durch Umsetzung von 1,1-Bis(hydroxymethyl)ferrocen mit Dithiolen dargestellt, welche Sauerstoff in den Alkylketten enthalten. Die Reaktion von 1,1-Bis(-hydroxyethyl)ferrocenen mit Dithiolen führte zu Mischungen von Diastereomeren, aus welchen reine Stereoisomere isoliert und charakterisiert wurden. Einige Aspekte des stereochemischen Verlaufes dieser Reaktionen werden diskutiert.

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Diastereomere oxathia[n](1,1)ferrocenophane

Novel oxathiaferrocenophanes have been synthesized by the reaction of 1,1-bis(hydroxymethyl)ferrocene with dithiols bearing oxygen in chains. The reactions of 1,1-bis(-hydroxyethyl)ferrocenes with dithiols afforded mixtures of diastereomeric products from which pure stereoisomers were isolated and characterized. Some aspects concerning a stereochemical course of the reactions described are discussed.

     

The structures of 1-(2′-hydroxybenzoyl)piperidine and 4-(2′-hydroxybenzoyl)morpholine

1-(2-hydroxybenzoyl)piperidine, C₁₂H₁₅NO₂, orthorhombic, Pbc2₁-C _2v ⁵ ;a=9.529 (1),b=10.001 (1),c=11.652 (1) Å;Z=4. The structure was determined from 1 510 single crystal X-ray data by direct methods and the refinement of the structure parameters yieldedR=0.040. There is one molecule in the asymmetric unit.4-(2-hydroxybenzoyl)morpholine, C₁₁H₁₃NO₃, orthorhombic, P2₁2₁2₁-D ₂ ⁴ ;a=13.006 (1),b=17.258 (2),c=9.125 (1) Å;Z=8. The structure parameters of the isotypic compound 4-(2-hydroxythiobenzoyl)morpholine were used in a starting set of refinement; finallyR=0.054 was obtained for 1 900 single crystal X-ray data. There are two molecules in the asymmetric unit.In both compounds the hydrogen atoms could be located by means of differenceFourier summations. The intermolecular hydrogen bonds with O ... O distances of 2.649 (2) Å for the piperidine derivate and 2.688 (3) resp. 2.754 (3) Å for the morpholine derivate are typical for intermediate bond strengths.

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Die Strukturen von 1-(2-hydroxybenzoyl)piperidin und 4-(2-hydroxybenzoyl)morpholin

Zusammenfassung 1-(2-hydroxybenzoyl)piperidin, C₁₂H₁₅NO₂, orthorhombisch, Pbc2₁-C _2v ⁵ ;a=9.529 (1),b=10.001 (1),c=11.652 (1) Å;Z=4. Die Struktur wurde aus 1 510 Einkristallröntgendaten mittels direkter Methoden bestimmt; die Strukturverfeinerung ergabR=0.040. Es ist ein Molekül in der asymmetrischen Einheit.4-(2-hydroxybenzoyl)morpholin, C₁₁H₁₃NO₃, orthorhombisch, P2₁2₁2₁-D ₂ ⁴ ;a=13.006 (1),b=17.258 (2),c=9.125 (1) Å;Z=8. Die Strukturparameter der isotypen Verbindung 4-(2-hydroxythiobenzoyl)morpholin wurden als Startsatz für die Strukturverfeinerung benutzt. Es wurdeR=0.054 aus 1 900 Einkristallröntgendaten erreicht. Es befinden sich zwei Moleküle in der asymmetrischen Einheit.In beiden Verbindungen konnten mittels Differenz-Fourier-Summierungen die Wasserstoffatome lokalisiert werden. Die intermolekularen Wasserstoffbrükken mit O ... O-Distanzen von 2.649 (2) Å für das Piperidinderivat und 2.688 (3) bzw. 2.754 (3) Å für das Morpholinderivat sind typisch für mittlere Bindungsstärken.

     

Lumineszierende Cu(I)- und Ag(I)-Cluster mit Thionoliganden

Zusammenfassung Cu(I) bildet mit zahlreichen nicht lumineszierenden Thionoliganden (N-monosubstituierten N-Sulfonylthioharnstoffen, N,N-Dialkyl-N-phenylthioharnstoffen und N,N-Dialkylmonothiocarbamaten) rot lumineszierende oktaedrische Cluster (CuL)₆. Die Lumineszenz tritt sowohl im Festzustand als auch in Lösungen auf. Abklingzeiten von 10^–5s deuten auf kurzlebige Phosphoreszenz hin. Der Einfluß verschiedener Strukturelemente auf die Lage der Emissionsmaxima wird diskutiert. Dabei bewirken Veränderungen in der Metall-Ligand-Koordination die stärkste Verschiebung der Lumineszenzbanden. Tetraedrische (CuL)₄-Cluster mit den obigen Thionoliganden zeigen keine Lumineszenz. Generelle Unterschiede in der Struktur oktaedrischer und tetraedrischer Cluster werden diskutiert.Ag(I) bildet nur mit N-Alkyl-N-sulfonylthioharnstoffen lumineszierende Cluster (AgL)₆. Die Lumineszenz ist im Gegensatz zu den Cu-Clustern auf den Festzustand beschränkt.

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Luminescent Cu(I) and Ag(I) clusters with thiono ligands

Summary Octahedrical (CuL)₆ clusters with several non luminescent thiono ligands (N-monosubstituted N-sulfonylthioureas, N,N-dialkyl-N-phenylthioureas and N,N-dialkylmonothiocarbamates) show red luminescence in the solid state and in solution. The luminescence lifetimes of 10^–5s are typical of short lived phosphorescence. The emission bands are affected by structural variation of the ligand. Changes of the coordination bonds cause the strongest shifts of the luminescence maxima. Tetrahedrical (CuL)₄ clusters with the same thiono ligands are not luminescent. General structural differences between octahedral and tetrahedral clusters are discussed.(AgL)₆ clusters are only luminescent in the solid state and if the ligand is a N-monosubstituted N-sulfonylthiourea

     

[2+2]-Photocycloaddition von Cyclohexen an 2-Acetyl-5,5-dimethyl-1,3-cyclohexandion und 3-Acetyl-1,5,5-trimethyl-2,4-pyrrolidindion

Summary Irradiation of solutions of excess cyclohexene and 2-acetyl-5,5-dimethyl-1,3-cyclohexanedione (1), and 3-acetyl-1,5,5-trimethyl-2,4-pyrrolidinedione (4) results mainly in the formation of 1,5-diones2 and5. These originate from intermediate cycloadducts of cyclohexene and theexo-enols of the cyclic 1,3-diketones. The yields decrease with increasing polarity of the solvent. In solution2 and5 are in equilibrium with the cyclic hemiacetales3 and6.

     

Asymmetric reduction of acetophenone and propiophenone by NaAl(IPTOLate)H2 combined with enantiomeric enrichment of the reaction product as an inclusion complex with IPTOL

An improved procedure was developed for asymmetric reduction of acetophenone and propiophenone by the chiral reagent NaAl(IPTOLate)H₂. This procedure is based on isolation of the chiral alcohol that formed as a crystalline host—guest complex with the IPTOL ligand. The enantiomeric enrichment of the product was as high as 97% ee. The ability of IPTOL and its analogs to form host—guest complexes with a number of ether-type solvents, 1-phenylethanol, and 1-phenylpropan-1-ol as well as thermal stabilities of IPTOL-containing complexes with these alcohols were studied.     

Synthesis and thermal decomposition of 3-aroyl-4-aryl-2-pyrazolines

Summary 3-Aroyl-4-aryl-2-pyrazolines (21–40) have been synthesized by the reaction of ,-unsaturated ketones (1–20) with diazomethane. These 2-pyrazolines gave -methyl-,-unsaturated ketones (41–46) on thermal denitrogenation.Dedicated to Prof. Dr.F. Sauter on the occasion of his 65^th birthday     

Aromatische Spirane. 15. Mitt. Darstellung von 2,2′-Spirobi-(s-hydrindacen)-1,1′-dion und von 4,4′-disubstituierten 2,2′-Spirobi-(s-hydrindacenen)

The title compound6 a was prepared by cyclisation of the diacid4 b. The diester4 a of4 b was synthesized by alkylation of2 with3 and following Retro-Claisen-reaction. After catalytic reduction of6 a to8 a two identical substituents were introduced byFriedel-Crafts-reaction (28). By transformation of the acetylgroups several other derivates (29–36) could be obtained. The unsymmetrical compounds (e.g.21) were prepared from20, whose precurser was the spiroketon10 a.

     

N-Arylsulfonyl-N′-pyrimidinylsubstituierte Chloralaminale

N-Arylsulfonyl-N-pyrimidinyl substituted aminals of chloral were prepared from N-(1-Hydroxy-2,2,2-trichloroethyl)arylsulfonamides with thionyl chloride and subsequent reaction with aminopyrimidines.

     

Thermal Behaviour of the N-donor Adducts of Metal Saccharinates: I. 2,2'-bipyridine saccharinato complexes of Co(II), Ni(II), Cu(II), Zn(II) and Pb(II)

The adducts of Co, Ni, Cu, Zn and Pb saccharinates with 2,2'-bipyridine were synthesized and their thermal behaviour in the 20–1000°C temperature interval in a static air atmosphere was investigated. Regardless of the coordination, the decomposition starts with dehydration and proceeds with removal of the bipyridine ligand(s). The resulting metal(II) saccharinates adopt characteristic two-step decomposition, the first step being the SO₂ release. Their stability was found tobe metal-dependent. The thermal decomposition pathways were correlated with the existing structural data about the compounds.This revised version was published online in November 2005 with corrections to the Cover Date.     

N-(2,6-Dihalobenzoyl)-N′-pyrimidinylharnstoffe

N-(2,6-Dichlorobenzoyl)- and N-(2,6-difluorobenzoyl)-N-pyrimidinylureas3b–3n have been synthesized by reaction of the corresponding aminopyrimidine derivatives with 2,6-dichlorobenzoyl isocyanate or 2,6-difluorobenzoyl isocyanate. The insecticidal activity of compounds3b–3n has been evaluated.

     

Reaction of 2-methyl-4,5-dihydrofuran with hydrogen chloride

Reaction of 2-methyl-4,5-dihydrofuran with HCl at 0°C yields 5-chloro-2-pentanone (13%) and 1-(2-methyltetrahydrofuryl-2)-5-chloro-2-pentanone (27%) and at 200° 5-chloro-2-pentanone exclusively.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. I. M. Gubkin State Petroleum and Gas Academy, 117917 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 2188–2191, September, 1992.     

Transition Metal Halide Salts of 1,3-bis(4-Pyridyl)propane: Synthesis and Structural Characterization

The resulting salts of (H₂bpp)MX₄ · n H₂O (M = Zn, X = Cl, n = 1, 1; M = Cd, X = Br, n = 0, 2; M = Hg, X = Cl, n = 1, 3; M = Cu, X = Cl, n = 0, 4; M = Cu, X = Br, n = 1, 5; M = Pt, X = Cl, n = 1, 6) were crystallized from the reaction mixture prepared by adding MX₂ to the HX solution of 1,3-bis(4-pyridyl)propane (bpp), while the salt of colorless (H₂bpp)SnCl₆, 7, was crystallized from the reaction mixture prepared by adding SnCl₂ to the HCl solution of bpp. Their structures have been determined by X-ray crystallography. All the compounds show supramolecular structures in the solid state by intermolecular hydrogen bondings and aromatic – interactions. The H₂bpp²⁺ cations in these metal salts adopt the gauche–gauche and anti–anti conformations with different dihedral angles for the two pyridyl rings.     

Synthesis of 2′,3′-dideoxynucleosides from 5-alkoxymethyluracils

Summary A modified synthesis of protected 2,3-dideoxyribose5 starting fromL-glutamic acid (1) is described. Reaction of5 with silylated 5-hydroxymethyluracil7 a and 5-alkoxymethyluracils7 b–e in the presence of trimethylsilyl triflate afforded an anomeric mixture of 2,3-dideoxyuridine derivatives8 a–e and9 a–e. Deprotection with methanolic ammonia and separation by chromatography gave the corresponding nucleosides10 a–e and11 a–e. Treatment of9 b–e with tri(1H-1,2,4-triazol-1-yl)phosphine oxide and subsequent reaction of12 b–e with ammonia in dioxane afforded the cytosine derivatives13 b–e which on treatment with methanolic ammonia gave the corresponding 2,3-dideoxycytidine derivatives14 b–e and15 b–e. In contrast with the parent compounds, these alkoxymethyl derivatives had no appreciable activity against human immunodeficiency virus (HIV-1).

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Synthese von 2,3-Dideoxynucleosiden aus 5-Alkoxymethyluracilen

Zusammenfassung Ausgehend vonL-Glutaminsäure (1) wird eine modifizierte Synthese von geschützter 2,3-Dideoxyribose (5) beschrieben. Reaktion von5 mit silyliertem 5-Alkoxymethyluracilen7 b–e in Gegenwart von Trimethylsilyltriflat ergab anomere Mischungen der 2,3-Dideoxyuridinderivate8 a–e und9 a–e. Abspaltung der Schutzgruppe mit methanolischen Ammoniak und chromatographische Trennung ergab die entsprechenden Nucleoside10 a–e und11 a–e. Behandlung von9 b–e mit Tri(1H-1,2,4-triazol-1-yl)phosphinoxid und nachfolgende Reaktion von12 b–e mit Ammoniak in Dioxan ergab die Cytosinderivate13 b–e, welche nach Behandlung mit methanolischem Ammoniak die entsprechenden 2,3-Dideoxycytidinderivate14 b–e und15 b–e ergaben. Im Gegensatz zur Stammverbindung hatten diese Alkoxymethylderivate keine nennenswerte Wirksamkeit gegen den menschlichen Immunschwächevirus (HIV-1).

     

Natural product chemistry. Part 121. Synthesis of dicoumarinyl ethers with the structures proposed for fatagarine and oreojasmine

Synthesis of the 7,8-dicoumarinyl ethers: 7-methoxy-7,8-oxydicoumarin and 6,7-dimethoxy-7,8-oxydicoumarin, established that the structures of fatagarine and oreojasmine for which these two structures have been proposed, have to be revised. Synthesis of 7-methoxy-5,7-oxydicoumarin and 8-methoxy-7,7-oxydicoumarin exclude the possibility of these dicoumarinyl ether structures for fatagarine.

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Naturstoffchemie. 121. Mitt.: Synthese von Dicumarinylethern mit den für das Fatagarin und das Oreojasmin vorgeschlagenen Strukturen

Zusammenfassung Durch die Synthese der 7,8-Dicumarinylether: 7-Methoxy-7,8-oxydicumarin und 6,7-Dimethoxy-7,8-oxydicumarin, ließ sich nachweisen, daß die für das Fatagarin und Oreojasmin vorgeschlagenen Strukturen revidiert werden müssen. Die Darstellung des 8-Methoxy-7,7-oxydicoumarin und 7-Methoxy-5,7-oxydicumarin schließen die Möglichkeit dieser Strukturen für das Fatagarin aus.

     

Spin-crossover complexes in solution. III. Substituent- and solvent effects on the spin-equilibrium of 4-substituted iron(II)-2,6-bis-(benzimidazol-2′-yl)-pyridine systems

Summary Transition metal complexes of the composition [Fe(4-X-bzimpy)₂](ClO₄)₂ [bzimpy = 2,6-bis-(benzimidazol-2-yl)pyridine and X=H, OH, Cl] show thermally accessible spin-crossover behaviour in solution that depends on both the ligand and the solvent.¹H-NMR spectroscopy and UV-visible spectroscopy measurements suggest that ligand substituent effects, solvent donor-acceptor properties and hydrogen-bonding may be employed to fine-tune the ligand field strength and hence to affect the spin-crossover behaviour. The ligand substitution changes in solution are reflected by the magnetic data (X=H:_exp=2.50 _B; X=OH:_exp=4.20 _B and X=Cl:_exp=4.30 _B at 294 K in MeOH), and by the shift of metal-to-ligandcharge-transfer band (X=H, =557 nm; X=OH, =520 nm; X=Cl, =500 nm). [Fe(bzimpy)₂](ClO₄)₂ exhibits a pronounced spin-crossover equilibrium (¹A₁ ⁵T₂) in solution (K _sc=0.26 at 293 K; _exp=1.30 3.40 _B for 213 328 K in MeOH). A small variation of magnetic moments of [Fe(4-OH-bzimpy)₂](ClO₄)₂ (_exp=3.77 4.73 _B at 220 332 K) might indicate either the existence of (temperature dependent) hydrogen bonding between the ligand and solvent molecules or a temperature dependent variation in the population of the⁵E_g sublevel. The presence of strong donor solvents (DN 30) shifts the spin-state of the complexes.In course of absence from the Chemistry Department, Jahangirnagar University, Dhaka, Bangladesh     

Investigation of polyimide formation from the complexes of the diester of benzophenonetetracarboxylic acid with diamines 7. Role of theo-carboxylic group of acid diester in the formation and imidization of H-complexes

The kinetics of thermal imidization of various H-complexes of semiesters of bis(o-phthalic) acids with diamines was studied. The activation energy of the imidization was shown to increase with increasing pK_a value of the diamine andE _a value of the dianhydride and with decreasing nucleophilicity of the alcohol used for the synthesis of H-complexes. The experimental kinetic data and the results of quantum chemical calculations of the heats of formation of the initial H-complexes and transition states made it possible to propose a mechanism for the imidization reaction. This mechanism takes into account the catalytic effect of the carboxylic group of the semiester in theo-position with respect to the ester group.For report 6, seeIzv. Akad. Nauk, Ser. Khim., 1993, 300 [Russ. Chem. Bull., 1993,42, 255 (Engl. Transl.)].Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1060–1065, June, 1995.