Synthesis and molecular structures of cyclopentadienyl sulfide complexes of chromium with cymantrenyl-thiolate bridging ligands

Interaction of [Cp₂Cr₂(CO)₄[μ-SC₅H₄Mn(CO)₃]₂ with sulphur gave binuclear complex Cp₂Cr₂[μ-SC₅H₄Mn(CO)₃]₂(μ-S) (I) (Cp = π-C₅H₅) and triangular cluster Cp₃Cr₃[μ-SC₅H₄Mn(CO)₃](μ-S)₂(μ₃-S) (II). I was also synthesized from Cp₂Cr₂(μ-SCMe₃)₂(μ-S) and (CO)₃Mn(C₅H₄SH). Interaction between I and Co₂(CO)₈ resulted in triangular mixed-metal cluster Cp₂Cr₂[μ-SC₅H₄Mn(CO)₃](μ³-S)₂Co(CO)₂ (III). The molecular structures of I–III were determined by means of single-crystal X-ray diffraction analysis.     

Synthesis and characterization of chromium and tungsten tetracarbonyl bound to the bridging ligand 2,3-bis(2-pyridyl)pyrazine (dpp)

The synthesis, electronic absorption, infrared and ¹³C NMR spectra, and electrochemistry of [Cr(CO)₄]dpp and [W(CO)₄]dpp (dpp = 2,3-bis(2-pyridyl)pyrazine) are reported. Electronic absorption spectra in different solvents show solvatochromic behavior and indicate the metal to ligand charge transfer (MLCT) excited state is lower in energy than the ligand field (LF) excited state. Electrochemical results show the [Cr(CO)₄]dpp complex undergoes semi-reversible one electron oxidation, while [W(CO)₄]dpp undergoes irreversible one electron oxidation. ¹³C NMR spectra of both complexes show all carbons in the metal-bound dpp ring shift downfield. The amount of downfield shift for the series [M(CO)₄]dpp (M = Cr, Mo, W) is interpreted as indicating better M dπ → dpp pπ backbonding occurs for Mo and W than for Cr.     

Synthesis and application of chalcones to the preparation of heterocyclic structures

Condensation of methyl N-(4-acetylphenyl)carbamate with aromatic aldehydes in basic and acid environment, and also with hetarylaldehydes in the presence of bases afforded chalcones with the carbamate function. Under the conditions of basic catalysis a nucleophilic substitution was observed of a methoxy group in the carbamate moiety of the chalcone for an ethoxy group. The reactions of the obtained chalcones with hydrazine hydrate, isonicotinic acid hydrazide, guanidine and hydroxylamine hydrochlorides, thiourea, and selenium dioxide furnished the corresponding derivatives of pyrazole, oxazole, pyrimidine, and selenadiazole.     

Heterocyclic analogs of 5,12-naphthacenequinone. 5. Synthesis of 2,3-diamino-1,4-dimethoxyanthraquinone and its heterocyclic derivatives

A new method for the synthesis of 2,3-diamino-1,4-dimethoxyanthraquinone from quinizarin has been developed. Heterocyclic analogs of 5,12-naphthacenequinone have been synthesized based on this o-diamine-4,11-dimethoxyanthra[2,3-d]imidazole-5,10-dione, 4,11-dimethoxyanthra[2,3-d][1,2,3]triazole-5,10-dione, and 5,12-dimethoxynaphtho[2,3-g]quinoxaline-6,11-dione. On the 70th Birthday of Professor E. Lukevics. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No.1, 96–102, January 2007.     

Synthesis and molecular structures of heterometallic complexes [RC5H4Fe(CO)2]2 Sn(TePh)2 and their adducts with chromium and tungsten carbonyls or with trimethylplatinum iodide

Complexes [RC₅H₄Fe(CO)₂]₂Sn(TePh)₂ (R=H, Me) containing stable heterometallic Fe−Sn−Fe fragments with two phenyltellurium groups at the tin atom were synthesized from [RC₅H₄Fe(CO)₂]₂SnCl₂ (R=H, Me) and sodium phenyltelluride and their structures were established by X-ray analysis. Their chelates with tungsten tetracarbonyl, [RC₅H₄Fe(CO)₂]₂Sn(TePh)₂[W(CO)₄] (R=Me, H), and complexes with two Cr(CO)₅ fragments or dimeric trimethylplatinum iodide were synthesized and studied by X-ray analysis. Thermal decomposition of [RC₅H₄Fe(CO)₂]₂Sn(TePh)₂ complexes and their adducts with ML fragments (ML=W(CO)₄, 2 Cr(CO)₅, (Me₃PtI)₂) into inorganic tellurides of a preset mixed-metal—chalcogenide composition was studied by differential scanning calorimetry. The temperature of complete elimination of organic fragments from methylcyclopentadienyl complexes is about 100°C lower than in the case of cyclopentadienyl analogs. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1766–1772, September, 1999.     

Chemistry of 2-methylene-2,3-dihydro-3-furanones. 6. Crystal and molecular structures of 2-methoxycarbonylmethylene-5-phenyl-2,3-dihydrofuran-3-one

The crystal and molecular structures of 2-methoxycarbonylmethylene-5-phenyl-2,3-dihydrofuran-3-one have been analyzed by x-ray crystallography. The solid-phase photodimerization of this compound has been found to be topochemical in nature.For previous communication, see [1].Institute of Chemical Physics, Russian Academy of Sciences, Chernogolovka 142432. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 620–624, March, 1992.     

Variable-energy photoelectron spectroscopy of substituted rhenium and manganese pentacarbonyls: molecular orbital assignments and the interatomic resonant effect

High-resolution variable-energy photoelectron spectra of M(CO)5X [M = Re, X = Re(CO)5, Cl, Br, and I; and M = Mn, X = Mn(CO)5 and Br] are reported. Tunable synchrotron radiation is used to distinguish the Re 5d and Br 4p orbital based peaks for the controversial Re(CO)5Br. Our results provide firm molecular orbital assignments for all of these molecules. The valence orbital in the ordering of ionization energies for M(CO)5Cl (M = Mn and Re) and Mn(CO)5Br is a 1(M-X) > e(X) > b2(M) > e(M); but for M(CO)5I (M = Mn and Re) and Re(CO)5Br the ordering is a1(M-X) > e(M) > b2(M) > e(X). The crossover of the HOMO in the Re molecules due to the change in the halogen electronegativities occurs at Re(CO)5Br. The metal np-->nd resonance is observed for all of these molecules. For molecules like M2(CO)10 (M = Re and Mn) and Mn(CO)5Br, the observation of this np-->nd resonance is useful in assigning the metal nd based orbitals in their valence level spectra. However, for molecules like Re(CO)5X (X = Br and Cl), a np-->nd type resonance is observed on bands arising from both Re 5d and halogen mp based orbitals. This new resonant effect on the ligand-based orbitals is shown to be mainly due to the interatomic resonant effect. The core and valence level chemical shifts of these compounds are treated using Jolly's approach to confirm the assignments for the valence level spectra of some of these molecules. The high-resolution inner valence and core level spectra of these compounds are reported. Broadening of Re 4f, Br 3d, and I 4d core level spectra is discussed. The Auger peaks are observed in the high-resolution, high-intensity Br 3d of Re(CO)5Br and I 4d of Re(CO)5I spectra.     

Crystal and molecular structures of methyl (2-hydroxy-3-oxo-5-p-tolyl-2,3-dihydrofuran-2-yl)acetate

Institute of Chemical Physics in Chernogolovka, Russian Academy of Sciences. Institute of Technical Chemistry, Russian Academy of Sciences. A. M. Gorkii Perm State University. Translated fromZhurnal Struktumoi Khimii, Vol. 36, No. 5, pp. 952–956, September–October, 1995.     

Synthesis of a novel heterocyclic system: 8-Fluro- 1,2,3,4,4a,10a-hexahydro-5H-[1]benzopyrano[2,3-c]pyridin-5-ol

The Synthesis of the title compound is described and its structure elucidated by ¹H nmr spectroscopy.     

Catalytic Synthesis of 5‐Substituted Tetrazoles: Unexpected Reactions and Products

Tetrazoles are incredibly useful organic molecules with a wide range of applications from medicinal chemistry as carboxylic acid isosteres to high energy density materials in space research. In an effort to develop an easy protocol for the synthesis of tetrazoles from nitriles, we used nano‐Ag‐TiO₂ as an efficient heterogeneous catalyst for the reaction of various nitriles and sodium azide to afford 5‐substituted tetrazoles in excellent yields. By this method, a wide variety of aryl nitriles underwent [3 + 2] cycloaddition to afford tetrazoles in excellent yields. Further reaction of tetrazoles with ethylchloroacetate resulted in the formation of expected products, except for a bis‐tetrazole, which underwent ring opening and subsequent reaction to afford an unusual product. The bis‐tetrazole also formed an unusual polymeric sodium complex in aq. NaOH solution. X‐ray crystallography revealed a distorted octahedral geometry for the complex, which forms a three‐dimensional network of chains interlinked by bis‐tetrazole moieties through a network of H‐bonds.     

Synthesis and molecular structures of tris(thio- and selenophenyl)stannyl complexes of cyclopentadienylcarbonylnitrosylmanganese and their reaction products with tungsten carbony

Reactions of CpMn(CO)(NO)SnCl₃ (I) with sodium benzenethiolate and sodium benzenesele-nolate gave orange crystals of the complexes CpMn(CO)(NO)Sn(EPh)₃, where E = S (II) or Se (III). Treatment of complex II with photochemically generated W(CO)₅(THF) yielded the adduct CpMn(CO)(NO)Sn(SPh)₃ · W(CO)₅ (IV). A similar treatment of complex III resulted in the formation of the ditungsten complex W₂(CO)₄(SePh)₆ (V) with transfer of all chalcogenate groups from tin to tungsten. In reactions of complexes II and III with a Pt₀ complex with phosphine and acetylene, (PPh₃)₂Pt(Ph₂C₂), the chalcogenate groups are transferred from tin. Only the known Pt(II) complexes (PPh₃)₂Pt(EPh)₂), where E= S (VI) or Se (VII). Molecular structures IV and V were characterized by X-ray diffraction. It has been found that the Mn-Sn bond in complex IV (2.5479(9) Å) is nearly the same length as that found earlier for complex II (2.5328(17) Å) and is substantially shorter than the sum of the covalent radii of Mn and Sn (2.78 Å). The Sn-S bond is noticeably lengthened (2.5217(11) Å) only for the S atom bound to tungsten (W-S, 2.5696(12) Å), while the other Sn-S bonds (2.4413(12) and 2.4291(12) Å) are virtually the same as in complex II (on average, 2.441 Å). Complex V contains the direct W-W bond (2.8153(16) Å) supplemented with four benzeneselenolate bridges in which the W-Se bonds (on average, 2.642(2) Å) are longer than the two terminal W-SePh bonds (2.571(2) Å). All the W-Se bonds are much shorter than the sum of the covalent radii of W and Se (2.82 Å).     

Synthesis and characterization of a chromium(V) cis-dioxo bis(1,10-phenanthroline) complex and crystal and molecular structures of its chromium(III) precursor

The first structurally characterized Cr(V) dioxo complex, cis-[CrV(O)2(phen)2](BF4) (2, phen=1,10-phenanthroline) has been synthesized by the oxidation of a related Cr(III) complex, cis-[Cr(III)(phen)2(OH2)2](NO3)3.2.5H2O (1, characterized by X-ray crystallography), with NaOCl in aqueous solutions in the presence of excess NaBF4, and its purity has been confirmed by electrospray mass spectrometry (ESMS), EPR spectroscopy, and analytical techniques. Previously reported methods for the generation of Cr(V)-phen complexes, such as the oxidation of 1 with PbO2 or PhIO, have been shown by ESMS to lead to mixtures of Cr(III), Cr(V), Cr(VI), and in some cases Cr(IV) species, 3. Species 3 was assigned as [CrIV(O)(OH)(phen)2]+, based on ESMS and X-ray absorption spectroscopy measurements. A distorted octahedral structure for 2 (CrO, 1.63 A; Cr-N, 2.04 and 2.16 A) was established by multiple-scattering (MS) modeling of XAFS spectra (solid, 10 K). The validity of the model was verified by a good agreement between the results of MS XAFS fitting and X-ray crystallography for 1 (distorted octahedron; Cr-O, 1.95 A; Cr-N, 2.06 A). Unlike for the well-studied Cr(V) 2-hydroxycarboxylato complexes, 2 was equally or more stable in aqueous media (hours at pH=1-13 and 25 degrees C) compared with polar aprotic solvents. A stable Cr(III)-Cr(VI) dimer, [Cr(III)(Cr(VI)O4)(phen)2]+ (detected by ESMS), is formed during the decomposition of 2 in nonaqueous media. Comparative studies of the oxidation of 1 by NaOCl or PbO2 have shown that [Cr(V)(O)2(phen)2]+ was the active species responsible for the previously reported oxidative DNA damage, bacterial mutagenicity, and increased incidence of micronuclei in mammalian cells, caused by the oxidation products of 1 with PbO2. Efficient oxidation of 1 to a genotoxic species, [Cr(V)(O)2(phen)2]+, in neutral aqueous media by a biological oxidant, hypochlorite, supports the hypothesis on a significant role of reoxidation of Cr(III) complexes, formed during the intracellular reduction of Cr(VI), in Cr(VI)-induced carcinogenicity. Similar oxidation reactions may contribute to the reported adverse effects of a popular nutritional supplement, Cr(III) picolinate.     

Carbonylation of Alkynyl Epoxides: Synthesis of 5-Hydroxy-2,3-dienoate Esters and 2,3-Dihydrofuran-3-ol Derivatives

The carbonylation of alkynyl oxiranes catalyzed by (MePh(2))(4)Pd in the presence of 20 atm of carbon monoxide in methanol gives methyl 5-hydroxy-2,3-pentadienoates in good yields. When the reaction is performed on alkynyl oxiranemethanol derivatives, 4,5-dihydrofuran-3-ol derivatives are obtained stereoselectively. These products arise from the spontaneous cyclization of a dihydroxyallenyl ester intermediate.     

取代环戊二烯基三羰基合铬(钼)卤化物η5-RC5H4(CO)3MX的合成及结构

由η^5^-RC5H4(CO)3MNa(1)(R=MeCO, MeO2C, EtO2C; M=Cr, Mo)与I3、三卤化磷(PX3, X=Cl, Br, I)、苯基二氯化膦或甲基二碘化胂反应, 可得金属卤化物η^5-RC6H4(CO)3MX(2a-2l)(M=Cr, X=I; M=Mo, X=Cl, Br, I)。鉴于1(R=MeO2C, M=Mo)与PCl3反应的中间物η^5-MeO2CC5H4(CO)3MoPCl2业已被析离, 并可转变为相应的氯化物η^5-MeO2CC5H4(CO)3MoCl(2g), 因此1与三卤化磷、苯基二卤化膦或甲基二碘化胂生成金属卤化物的反应很可能经缩合及中间物分解两步简单反应, 2f(R=MeCO, M=Mo, X=I)为单斜晶系, a=0.6663(2), b=1.2364(6), c=1.5464(5)nm; β=99.02(3)°;V=1.2581nm^3; Dc=2.186g/cm^3; Z=4; F(000)=776; 空间各P21/c。     

2,3—二取代—5—氟脲嘧啶的合成及其抗肿瘤活性研究

以相转移催化法或在无水体系中合成了十个未见文献报道了２，３－二取代５－氟脲嘧啶化合物，它们的结构经ＩＲ、＾ＨＮＭＲ元素分析或ＭＳ等确证。其中有些化合物具有一定的抗肿瘤活性。     

Synthesis and crystal structures of new lanthanide isonicotinates: coordination polymers and molecular complexes

New coordination polymers [Ce(C5H4NCOO)3(H2O)2] · 0.5C6H4N2 · 1.5H2O, [Ln(C5H4N-COO)3(H2O)2] (Ln = Ce, Pr) and [Ho(C5H4NCOO)2(H2O)4]NO3, and the tetranuclear complex [Ho4(OH)4(C5H4NCOO)6(H2O)8](NO3)2 · 3.5C6H4N2 · 5H2O were prepared by heating aqueous solutions of lanthanide(III) nitrates with 4-cyanopyridine under conditions of hydro-thermal synthesis. X-ray diffraction study demonstrated that the lanthanide atoms in the coordination polymers are bridged in chains through coordination to the carboxyl group of isonicotinic acid. The metal atoms in the tetranuclear complex are bound in pairs by six bidentate isonicotinate ligands.     

Ab initio studies of molecular structures,conformers and vibrational spectra of heterocyclic organics: I. Nicotinamide and its N-oxide

FTIR spectra of nicotinamide and its N-oxide have been recorded and analyzed in the range 400–4000 cm^?1. The stabilities, optimized molecular geometries, APT charges and vibrational characteristics for the two possible conformers of nicotinamide and its N-oxide have been studied theoretically using restricted Hartree–Fock (RHF) and density functional theory (DFT) methods. The E (trans) conformers of nicotinamide and its N-oxide are found to be more stable and less polar than their respective Z (cis) conformers. Due to addition of an O atom at the N₁ site in the NA molecule the magnitudes of atomic charges on all the H atomic sites are found to increase. For all the studied molecules, magnitude of the wagging mode of the NH₂ group is found to be higher than its torsion mode, which is in the reverse order as compared to that for the aniline molecule. Most of the vibrational frequencies have nearly the same magnitude for the two conformers of nicotinamide and its N-oxide, however, significant changes are noticed in their IR intensities, Raman activities and depolarization ratios of the Raman bands. The frequency of the ring breathing mode for the NA molecule is found to decrease by 100 cm^?1 in going to the NANO molecule for both the conformers. The IR intensity for the scissoring mode of the CON(H₂) group is found to decrease significantly for the NA-II conformer as compared to that for the NA-I conformer.     

Chemistry of iminofurans: XIV. Ring opening of 5-substituted furan-2,3-dione 3-benzoylhydrazones by the action of aromatic and heterocyclic amines

Reactions of 5-aryl- and 5-tert-butyl-3-(benzoylhydrazinylidene)furan-2,3-diones with aromatic and heterocyclic amines afforded 4-aryl-2-(benzoylhydrazinylidene)-4-oxobutanamides and 5,5-dimethyl-2-(benzoylhydrazinylidene)-4-oxohexanamides which exist in solution as mixtures of hydrazone and cyclic dihydropyrazole tautomers.