Dimolybdenum complexes containing anions of N,N′-bis(pyrimidine-2-yl)formamidine and N-(2-pyrimidinyl)formamide

The reactions of Mo₂(O₂CCH₃)₄ with different equivalents of N,N′-bis(pyrimidine-2-yl)formamidine (HL1) and N-(2-pyrimidinyl)formamide (HL2) afforded dimolybdenum complexes of the types Mo₂(O₂CCH₃)(L1)₂(L2) (1) trans-Mo₂(L1)₂(L2)₂ (2) cis-Mo₂(L1)₂(L2)₂ (3) and Mo₂(L2)₄ (4). Their UV–Vis and NMR spectra have been recorded and their structures determined by X-ray crystallography. Complexes 2 and 3 establish the first pair of trans and cis forms of dimolybdenum complexes containing formamidinate ligands. The L1 ligands in 1–3 are bridged to the metal centers through two central amine nitrogen atoms, while the L2 ligands in 1–4 are bridged to the metal centers via one pyrimidyl nitrogen atom and the amine nitrogen atom. The Mo–Mo distances of complexes 1 [2.0951(17) Å], 2 [2.103(1) Å] and 3 [2.1017(3) Å], which contain both Mo?N and Mo?O axial interactions, are slightly longer than those of complex 4 [2.0826(12)–2.0866(10) Å] which has only Mo?O interactions.     

Synthesis and biological activities of new 1H-1,2,4-triazole derivatives containing ferrocenyl moiety

Some new 1H-1,2,4-triazole derivatives containing ferrocenyl moiety were synthesized in various yields by the condensation of ferrocenecarboxaldehyde with 1-(1H-1,2,4-triazol-1-yl)-3-aryl-2-one in toluene. Their structures of all these new compounds have been confirmed with ¹H NMR, IR, MS and elemental analysis. Their results of bioassay showed that some title compounds exhibited some degree of antifungal and plant growth regulatory activities.     

Efficient one-pot formation of 4-N-substituted 2,4-dihydro-3H-1,2,4-triazolin-3-ones from primary amines using N′-(ethoxymethylene)hydrazinecarboxylic acid methyl ester

(E)-N′-(Ethoxymethylene)hydrazinecarboxylic acid methyl ester was synthesized in one step in good yield. This reagent was successfully applied to the one-pot synthesis of 4-substituted 2,4-dihydro-3H-1,2,4-triazolin-3-ones from readily available primary alkyl and aryl amines. This reaction process is relatively mild and easy to carry out. It is especially useful for the formation of sterically hindered triazolinones, which are otherwise difficult to obtain via existing literature procedures. A possible mechanistic pathway for the transformation is outlined.     

Synthesis and hybridization affinity of oligodeoxyribonucleotides incorporating 4-N-(N-arylcarbamoyl)deoxycytidine derivatives

Modified oligodeoxynucleotides incorporating 4-N-(N-arylcarbamoyl)-dC derivatives 1a-c were synthesized. The ¹H NMR spectra of 1a-c suggest that the carbamoyl group forms an intramolecular hydrogen bond with the cytosine ring nitrogen atom so that formation of a Watson-Crick base pair with the complementary guanine base is inhibited. The hybridization properties of oligodeoxynucleotides containing 1a-c were investigated by use of T_m analysis. The hybridization properties of 4-N-(N-phenylcarbamoyl)-dC (1a) were similar to those of 4-N-(N-alkylcarbamoyl)-dC derivatives reported previously. In sharp contrast to 1a, it turned out that 4-N-(N-napht-1-yl) and (N-quionol-5-yl)-dC (1b,c) have a unique property as a universal base.     

Highly efficient electrophilic cyclization of N′-(2-alkynylbenzylidene)hydrazides

Electrophilic cyclization of N′-(2-alkynylbenzylidene)hydrazides with I₂, Br₂, or ICl under mild conditions is described. This reaction proceeds smoothly in dichloromethane at room temperature, which provides a useful method for the synthesis of functionalized isoquinolinium-2-yl amide.     

1－（取代吡唑－4－基）－1，2，4－三唑的合成及生物活性研究

合成了２３个新的１－（取代吡唑－４－基）１，２，４－三唑化合物，经ＥＡ、ＩＲ、~１ＨＮＭＲ和ＭＳ确定其组成和结构，并对其进行了抑菌及生长调节活性的初步观察。     

N-(Pyridin-2-yl)picolinamide tetranickel clusters: Synthesis,structure and ethylene oligomerization

A series of N-(pyridin-2-yl)picolinamide derivatives was synthesized and characterized. Tetranickel complexes were obtained by stoichiometric reaction of NiBr₂ and corresponding ligands, and characterized by elemental and spectroscopic analysis. Moreover, the coordination pattern of complex 3a was confirmed by single-crystal X-ray diffraction. In the structure, two ligands linked two nickel atoms to form a unit, and two units were bridged via μ₃-OMe and μ₂-Br to form a tetranickel cluster. These Ni(II) complexes were investigated in ethylene oligomerization and found to exhibit remarkable catalytic activities upon activation with MAO. Reaction conditions as well as ligand environment significantly affected the catalytic performance of the nickel complexes; the highest activity could be achieved to be 2.7 × 10⁶ g mol⁻¹ Ni h⁻¹.     

Synthesis of 1-(2,4,6-trichlorophenyl)-2-(1,2,4-triazol-4-yl)-diazene-1-oxide

By reaction of 4-amino-1,2,4-triazole with 1-nitroso-2,4,6-trichlorobenzene in the presence of excess dibromoisocyanurate the title compound was obtained.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 362–364, February, 1992.     

Solvo-thermal Preparation and Characterization of Two CdII Coordination Polymers Constructed From 2,6-(1,2,4-Triazole-4-yl)pyridine and 5-R-Isophthalic Acid (R = Nitro,Sulfo)

Under the solvo-thermal conditions, two novel Cd^II mixed-ligand coordination materials with 2,6-(1,2,4-triazole-4-yl)pyridine(L₁) and aromatic poly-carboxylic acid co-ligands such as 5-R-isophthalic acid (R = nitro, sulfo), namely [Cd(L₁)(NO₂-BDC)(H₂O)₂] · 2H₂O ( 1 ) and [Cd(L₁)(HSIP)(H₂O)] · 4H₂O ( 2 ) (NO₂-H₂BDC = 5-nitroisophthalic acid, H₃SIP = 5-sulfobenzene -isophthalic acid) were successfully prepared. These Cd^II mixed-ligand coordination polymers 1 – 2 have been measured by crystal X-ray analysis, FT-IR spectra and powder X-ray diffraction analyses. In 1 , these seven-coordinate Cd^II atoms (Cd1) are inter-linked by didentate 5-nitroisophthalic acid ligands forming 1D chain structures. In 2 , these L₁ and partially de-pronated HSIP^2– are inter-linked by central Cd^II centers and are arranged into the unique 2D micro-porous metal-organic framework of 2 . Side view of 2 , it is noted that numerous oxygen atoms of un-coordinated carboxylate groups and coordinated SO₃ groups protrude out and decorate the 2D framework of 2 . PXRD patterns of 1 and 2 sample is tested, which is consistent with the simulated PXRD diffraction pattern. Photoluminescence studies show that 2 is highly selective and sensitive to trace elements of Eu³⁺ with excellent K_sv value (7.86 × 10⁴ m ^–1) and low detection limit (5.56 × 10^–2 mM), which also provides a convenient method and platform for real-time detection of Eu³⁺.     

Synthesis and characterization of a tetraruthenium butterfly cluster containing a quadruply-bridging ligand derived from an N,N′-dipyrid-2-ylurea

The tetraruthenium cluster complex [Ru₄(μ₄-κ⁴-dmpu)(CO)₁₀], H₂dmpu = N,N′-bis(6-methylpyrid-2-yl)urea, has been prepared by treating [Ru₃(CO)₁₂] with H₂dmpu in toluene at reflux temperature. An X-ray diffraction study has determined that this cluster has a butterfly metallic skeleton hold up by a doubly-deprotonated N,N′-bis(6-methylpyrid-2-yl)urea ligand (dmpu). This ligand has the pyridine N atoms attached to the wing-tip Ru atoms and the amido N atoms spanning Ru-Ru wing-edges, in such a way that the cluster has C₂ symmetry. The donor atoms of doubly-deprotonated N,N′-dipyrid-2-ylureas seem to be appropriately arranged to hold butterfly tetranuclear clusters.     

Catalytic photocarboxylation of 1,1-diphenylethylene with N,N,N′,N′-tetramethylbenzidine and carbon dioxide

Photocarboxylation of 1,1-diphenylethylene with N,N,N′,N′-tetramethylbenzidine (TMB) in MeCN under bubbling of CO₂ proceeded with high catalytic efficiency, giving 3,3-diphenylacrylic acid (DPA) and 3-hydroxy-3,3-diphenylpropionic acid (20). The turnover number (TON=(DPA+20)/TMB) reached 17. Similarly, 1-phenyl-1-cyclohexene yielded cis-2-acetamido-2-phenylcyclohexanecarboxylic acid with TON 5.9. As compared with related N,N-dimethylaniline derivatives, TMB is more resistant to photodecomposition, has the much larger absorbance in the S₀→S₁ transition, and has the lower quenching efficiency by CO₂. Probably these factors are partly responsible for the high TON observed for TMB.     

Synthesis, characterization and Schlenk equilibrium studies of methylmagnesium compounds with O- and N-donor ligands - the unexpected behavior of [MgMeBr(pmdta)] (pmdta = N,N,N′,N″,N″-pentamethyldiethylenetriamine)

MgMe₂ (1) was found to react with 1,4-diazabicyclo[2.2.2]octane (dabco) in tetrahydrofuran (thf) yielding a binuclear complex [{MgMe₂(thf)}₂(μ-dabco)] (2). Furthermore, from reactions of MgMeBr with diglyme (diethylene glycol dimethyl ether), NEt₃, and tmeda (N,N,N′,N′-tetramethylethylenediamine) in etheral solvents compounds MgMeBr(L), (L = diglyme (5); NEt₃ (6); tmeda (7)) were obtained as highly air- and moisture-sensitive white powders. From a thf solution of 7 crystals of [MgMeBr(thf)(tmeda)] (8) were obtained. Reactions of MgMeBr with pmdta (N,N,N′,N″,N″-pentamethyldiethylenetriamine) in thf resulted in formation of [MgMeBr(pmdta)] (9) in nearly quantitative yield. On the other hand, the same reaction in diethyl ether gave MgMeBr(pmdta) · MgBr₂(pmdta) (10) and [{MgMe₂(pmdta)}₇{MgMeBr(pmdta)}] (11) in 24% and 2% yield, respectively, as well as [MgMe₂(pmdta)] (12) as colorless needle-like crystals in about 26% yield. The synthesized methylmagnesium compounds were characterized by microanalysis and ¹H and ¹³C NMR spectroscopy. The coordination-induced shifts of the ¹H and ¹³C nuclei of the ligands are small; the largest ones were found in the tmeda and pmdta complexes. Single-crystal X-ray diffraction analyses revealed in 2 a tetrahedral environment of the Mg atoms with a bridging dabco ligand and in 8 a trigonal-bipyramidal coordination of the Mg atom. The single-crystal X-ray diffraction analyses of [MgMe₂(pmdta)] (12) and [MgBr₂(pmdta)] (13) showed them to be monomeric with five-coordinate Mg atoms. The square-pyramidal coordination polyhedra are built up of three N and two C atoms in 12 and three N and two Br atoms in 13. The apical positions are occupied by methyl and bromo ligands, respectively. Temperature-dependent ¹H NMR spectroscopic measurements (from 27 to −80 °C) of methylmagnesium bromide complexes MgMeBr(L) (L = thf (4); diglyme (5); NEt₃ (6); tmeda (7)) in thf-d₈ solutions indicated that the deeper the temperature the more the Schlenk equilibria are shifted to the dimethylmagnesium/dibromomagnesium species. Furthermore, at −80 °C the dimethylmagnesium compounds are predominant in the solutions of Grignard compounds 4-6 whereas in the case of the tmeda complex7 the equilibrium constant was roughly estimated to be 0.25. In contrast, [MgMeBr(pmdta)] (9) in thf-d₈ revealed no dismutation into [MgMe₂(pmdta)] (12) and [MgBr₂(pmdta)] (13) even up to −100 °C. In accordance with this unexpected behavior, 1:1 mixtures of 12 and 13 were found to react in thf at room temperature yielding quantitatively the corresponding Grignard compound 9. Moreover, the structures of [MgMeBr(pmdta)] (9c), [MgMe₂(pmdta)] (12c), and [MgBr₂(pmdta)] (13c) were calculated on the DFT level of theory. The calculated structures 12c and 13c are in a good agreement with the experimentally observed structures 12 and 13. The equilibrium constant of the Schlenk equilibrium (2 9c ? 12c + 13c) was calculated to be K_gas = 2.0 × 10⁻³ (298 K) in the gas phase. Considering the solvent effects of both thf and diethyl ether using a polarized continuum model (PCM) the corresponding equilibrium constants were calculated to be K_thf = 1.2 × 10⁻³ and K_ether = 3.2 × 10⁻³ (298 K), respectively.     

Micellar electrokinetic chromatography-chemiluminescent detection of biogenic amines using N-(4-aminobutyl)-N-ethylisoluminol as derivatization reagent and trivalent copper chelate as chemiluminescence enhancer

A facile, sensitive and universal method was established for analysis of biogenic amines using micellar electrokinetic chromatography coupled with chemiluminescent (CL) detection. It was found that diperiodatocuprate (III) (K₅[Cu(HIO₆)₂], DPC), a transition metal chelate at unstable high oxidation state, could effectively enhance the reaction between luminol-type compound and hydrogen peroxide, to produce very strong CL signal. In addition, triethylamine was found to be able to effectively improve the yield of the derivatization reaction between biogenic amines and a luminol-type derivatization reagent, N-(4-aminobutyl)-N-ethylisoluminol (ABEI). Based on these facts, three biogenic amines were pre-column derivatized with ABEI, and post-column detected using high sensitive luminol-hydrogen peroxide-DPC CL system. Since the background was quite low, and the signal was quite strong, a considerable improved sensitivity was obtained. The presented method had been successfully applied to simultaneously analyze glycine, proline and phenylalanine with the detection limits (S/N = 3) of 0.030 μmol L⁻¹, 0.23 μmol L⁻¹ and 0.21 μmol L⁻¹, respectively. To evaluate its potential application value, glycine in saliva and urine samples was detected using this method, and satisfied results were obtained. This approach can be further extended to detection of many other compounds such as peptides and drugs by using luminol-type derivatization reagent.     

Synthesis,spectral characterization of the zinc(II) mixed-ligand complexes of N(4)-allyl thiosemicarbazones and N,N,N′,N′-tetramethylethylenediamine,and crystal structure of the novel [ZnL2(tmen)] compound

Mixed-ligand zinc complexes with N,N,N′,N′-tetramethylethylenediamine (tmen) and R-salicylaldehyde N(4)-allyl thiosemicarbazones (R: 3-OCH₃ (L₁), 5-Br(L₂)), [ZnL_1,2(tmen)], were synthesized and the complexes were characterized by elemental analysis, atomic absorption spectrometer, magnetic susceptibility, molar conductivity, electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) mass spectra and IR, UV–Vis, ¹H NMR and ¹⁵N spectroscopies. Crystal of [ZnL₂(tmen)] have a slightly distorted square pyramid involving O, N, S atoms of thiosemicarbazone and one N atom of tmen in basal plane and the other N atom of tmen in apex of the pyramid. The non-coordinated allyl group is disordered.     

Lewis acid-catalyzed reactions of N′-(2-alkynylbenzylidene)hydrazides with diethyl phosphite

Lewis acid catalyst-tuned reactions of N′-(2-alkynylbenzylidene)hydrazides with diethyl phosphite are described. Isoquinolin-1-ylphosphonate is generated when copper triflate is utilized as catalyst, while 2-amino-1,2-dihydroisoquinolin-1-ylphosphonate is obtained in the presence of palladium acetate.     

Copper(I) catalysis: Synthesis of N,N′-diarylated and N-aryl,N′-formylated chiral C2-symmetric diamines

Chiral N,N′-diaryl C₂-symmetric diamines and N-aryl,N′-formyl-trans-(1R,2R)-diaminocyclohexane are readily accessed by copper catalyzed N,N′-diarylation and N-aryl,N′-formylation of trans-(1R,2R)-diaminocyclohexane with aryl bromides. N,N′-diarylation using (R)-1,1′-binaphthyl-2,2′-diamine and iodobenzene gave the corresponding (R)-N,N′-diphenyl-1,1′-binaphthyl-2,2′-diamine derivative in 83% yield.     

N,N′-Bis(aryl)pyridine-2,6-dicarboxamide complexes of ruthenium: Synthesis,structure and redox properties

Reaction of five N,N′-bis(aryl)pyridine-2,6-dicarboxamides (H₂L-R, where H₂ denotes the two acidic protons and R (R = OCH₃, CH₃, H, Cl and NO₂) the para substituent in the aryl fragment) with [Ru(trpy)Cl₃](trpy = 2,2′,2″-terpyridine) in refluxing ethanol in the presence of a base (NEt₃) affords a group of complexes of the type [Ru^II(trpy)(L-R)], each of which contains an amide ligand coordinated to the metal center as a dianionic tridentate N,N,N-donor along with a terpyridine ligand. Structure of the [Ru^II(trpy)(L-Cl)] complex has been determined by X-ray crystallography. All the Ru(II) complexes are diamagnetic, and show characteristic ¹H NMR signals and intense MLCT transitions in the visible region. Cyclic voltammetry on the [Ru^II(trpy)(L-R)] complexes shows a Ru(II)–Ru(III) oxidation within 0.16–0.33 V versus SCE. An oxidation of the coordinated amide ligand is also observed within 0.94–1.33 V versus SCE and a reduction of coordinated terpyridine ligand within −1.10 to −1.15 V versus SCE. Constant potential coulometric oxidation of the [Ru^II(trpy)(L-R)] complexes produces the corresponding [Ru^III(trpy)(L-R)]⁺ complexes, which have been isolated as the perchlorate salts. Structure of the [Ru^III(trpy)(L-CH₃)]ClO₄ complex has been determined by X-ray crystallography. All the Ru(III) complexes are one-electron paramagnetic, and show anisotropic ESR spectra at 77 K and intense LMCT transitions in the visible region. A weak ligand-field band has also been shown by all the [Ru^III(trpy)(L-R)]ClO₄ complexes near 1600 nm.     

Influence of N,N,N′,N′-tetraalkyl terephthalamide on isothermal crystallization kinetics and morphology evolution of polypropylene

The influence of N,N,N′,N′-tetraalkyl terephthalamide (TATA) on the isothermal crystallization kinetics of polypropylene (PP) was studied using differential scanning calorimetry (DSC). It was found that TATA shows a heterogeneous nucleation effect and leads to the formation of β-PP. TATA can not only shorten the crystallization time but also heighten the crystallization temperature of PP. The crystallization rate constant of PP containing TATA is larger than that of pure PP. The evolution of crystalline morphology of PP was investigated on a polarized optical microscopy (POM) equipped with a hot stage and the results showed that the introduction of TATA into PP can quicken the crystallization of PP, which is consistent with DSC results. TATA also leads to a substantial decrease in the spherulite size of PP and the boundaries of spherulites are hardly distinguished.     

Synthesis and hybridization properties of 2′-O-(tetrazol-5-yl)ethyl-modified oligonucleotides

2′-O-(1H-Tetrazol-5-yl)ethyladenosine was synthesized using 2′-O-cyanoethyladenosine derivative as a key intermediate. The 2′-O-(1H-tetrazol-5-yl)ethyl modifications exhibited intriguing properties such as the change in the structure of the tetrazole residue between a protonated and a deprotonated form. The T_m experiments of various oligodeoxynucleotides having a 2′-O-(1H-tetrazol-5-yl)ethyl-modified adenosine showed reduced hybridization affinity in comparison to the unmodified oligonucleotides toward their complementary oligodeoxynucleotides. The mechanism of the reduced hybridization affinity was discussed on the basis of the structure and the physicochemical properties of the tetrazole moiety.     

Complexes derived from the copper(II)/succinamic acid/N,N′,N″-chelate tertiary reaction systems: Synthesis,structural and spectroscopic studies

The use of succinamic acid (H₂sucm) in Cu^II/N,N′,N″-donor [2,2′:6′,2″-terpyridine (terpy), 2,6-bis(3,5-dimethylpyrazol-1-yl)pyridine (dmbppy)] reaction mixtures yielded compounds [Cu(Hsucm)(terpy)]_n(ClO₄)_n (1), [Cu(Hsucm)(terpy)(MeOH)](ClO₄) (2), [Cu₂(Hsucm)₂(terpy)₂](ClO₄)₂ (3), [Cu(ClO₄)₂(terpy)(MeOH)] (4), [Cu(Hsucm)(dmbppy)]_n(NO₃)_n·3nH₂O (5^.3nH₂O), and [CuCl₂(dmbppy)]·H₂O (6·H₂O). The succinamate(−1) ligand exists in four different coordination modes in the structures of 1–3 and 5, i.e., the μ₂-κO:κO′:κO″ in 1 and 5 which involves asymmetric chelating coordination of the carboxylato group and ligation of the amide O-atom leading to 1D coordination polymers, the μ₂-κ²O:κO′ in 3 which involves asymmetric chelating and bridging coordination of the carboxylato group, and the asymmetric chelating mode in 2. The primary amide group, either coordinated in 1 and 5, or uncoordinated in 2 and 3, participate in hydrogen bonding interactions, leading to interesting crystal structures. Characteristic IR bands of the complexes are discussed in terms of the known structures and the coordination modes of the Hsucm⁻ ligands. The thermal decomposition of complex 5·3nH₂O was monitored by TG/DTG and DTA measurements.