Zinaida S. Klemenkova

Vibrational spectra of tris(cyclopentadienyl)zirconium and -hafnium hydrides and deuterides, Cp3MX (M Zr, Hf; X H, D)

The synthesis has been performed of tris(cyclopentadienyl)hafnium hydride and deuteride from Cp4Hf treated with LiAlH4 and LiAlD4, respectively. The IR spectra (4000—100 cm-1) and Raman spectra of tris(cyclopentadienyl)zirconium and -hafnium hydrides and deuterides have been studied. The compounds are shown to have the structure (η5-C5H5)3MX (M  Zr, Hf; X  H, D) with three identically bonded cyclopentadienyl ligands. The spectral characteristics obtained are consistent with metal—ring coordination of the central type. An increase is noted in the strength of the M—H and M—Cp bonds when passing from zirconium to hafnium.

Study of the catalytic activity of electrochemically reduced forms of phthalocyanines in the reaction of CO2 with epoxides

Catalytic activity of electrochemically reduced forms of mono- and diphthalocyanine complexes of transition and rare-earth elements in the reaction of carbon dioxide with epoxides is considerably higher than that of corresponding neutral forms. The catalytic efficiency depends on the nature of the phthalocyanine complex, the method of the catalyst immobilization, and the electrophilicity of epoxide.

Interaction of carbon dioxide with zirconocene and hafnocene dihydrides

Zirconocene and hafnocene dihydrides Cp2MH2 (M = Zr, Hf) are capable of rapid absorbing carbon dioxide at room temperature and atmospheric pressure in a THF medium. In the case of Cp2ZrH2, the reaction results in the cleavage of the C=O bond of a CO2 molecule to form cyclic trimeric zirconocene oxide [Cp2ZrO]3, whose structure was confirmed by analytical and spectral methods as well as by X-ray diffraction study. Small amounts of formaldehyde and methyl formate are found in the organic products of the reaction.

Synthesis and Complexing Properties of Phosphorus-Substituted Pyridine-2-Carboxylic Acid Anilides

Abstract Novel phosphorus-containing ligands have been synthesized by the condensation of 2-(thio)phosphorylated anilines with 2,6-dichloro- and 4-chloropyridine-2-carbonyl chlorides in the presence of Et3N and unsubstituted pyridine-2-carboxylic acid using P(OPh)3 as a coupling agent. The compounds derived readily form complexes with a range of transition metals (M=Re(I), Pd(II), and Cu(II)), serving as bi- or tridentate monoanionic ligands. The composition and structure of the resulting metallocycles depend both on the presence/amount of the Cl atoms in the pyridine ring and on the nature of the donor atom X in the P=X moiety. The novel compounds were characterized by multinuclear NMR and IR spectroscopy as well as X-ray crystallography. GRAPHICAL ABSTRACT

Influence of ligand architecture on the structure of coordination centre in dimeric europium carboxylates with 1,10-phenanthroline

Abstract Methods of optical spectroscopy and X-ray crystallography data were used to examine the effect of architecture of carboxylate anions on structure of the Eu3+ coordination centre in europium carboxylates with 1,10-phenanthroline Eu(RCOO)3·Phen. Luminescence spectra of europium acetate, nitropropionate, benzoate, naphthylcarboxylates, phenylacetates, phenoxyacetate, triphenylpropionate were investigated. A few of europium carboxylates with 2,2′-bipyridine Eu(RCOO)3·Bpy and europium salts Eu(RCOO)3·nH2O were also studied. Vibrational IR and Raman spectra of phenylacetate family were analyzed. The crystal structure of nitropropionate Eu(NO2C2H4COO)3·Phen was solved by X-ray diffraction method. The predominant influence of steric hindrances on Eu3+ coordination centre was observed at increase of the size of aromatic fragment of carboxylate anions. It was demonstrated, that introduction of the methylene bridges between the carboxylic group and aromatic rings of ligand weakens the effect of steric factor.

1,5-Diaryl-3-oxo-1,4-pentadienes based on (4-oxopiperidin-1-yl)(aryl)methyl phosphonate scaffold: synthesis and antitumor properties

Novel 3,5-bis(arylidene)-4-piperidones modified with diethyl[(aryl)methyl]phosphonate moiety attached to the piperidone nitrogen atom have been synthesized by crotonic condensation of aromatic aldehydes with diethyl[(4-oxopiperidin-1-yl)(aryl)methyl]phosphonates in the presence of LiClO4/Et3N system or acetonitrile solution of boron trifluoride etherate. The synthesized phosphonate derivatives of 3,5-bis(arylidene)-4-piperidone series displayed inhibitory properties toward RD, PC3, HCT116, and MCF7 human cancer cell lines with IC50 values in the range of 2.5–8.5 μM, as assessed by an in vitro 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.

Highly Cytotoxic Palladium(II) Pincer Complexes Based on Picolinylamides Functionalized with Amino Acids Bearing Ancillary S-Donor Groups

The reactions of picolinyl and 4-chloropicolinyl chlorides with methyl esters of S-methyl-l-cysteine, l- and d-methionine, and l-histidine afforded a series of functionalized carboxamides, which readily formed pincer-type complexes upon interaction with PdCl2(NCPh)2 in solution under mild conditions. The direct cyclopalladation of the ligands derived was also accomplished in the solid phase, in particular, mechanochemically, although it was complicated by the partial deactivation of the starting amides. The resulting complexes with 5,5- and 5,6-membered fused metallocycles were fully characterized by IR and NMR spectroscopy, including variable-temperature and 2D-NMR studies. In the case of some cysteine- and methionine-based derivatives, the realization of κ3-N,N,S-coordination was supported by X-ray diffraction. The cytotoxic effects of these complexes were examined on HCT116, MCF7, and PC3 human cancer cell lines as well as HEK293 as a representative of normal cells. The comparative studies allowed us to determine that the presence of the sulfide ancillary donor group is crucial for cytotoxic activity of this type of Pd(II) complexes. The main structure-activity relationships and the most promising palladocycles were outlined. The additional studies by gel electrophoresis revealed that 4-chloropicolinyl derivatives, despite the nature of an amino acid, can bind with DNA and inhibit topoisomerase I activity.

Synthesis of camphecene derivatives using click chemistry methodology and study of their antiviral activity

A series of seventeen tetrazole derivatives of 1,7,7-trimethyl-[2.2.1]bicycloheptane were synthesized using click chemistry methodology and characterized by spectral data. Studies of cytotoxicity and in vitro antiviral activity against influenza virus A/Puerto Rico/8/34 (H1N1) in MDCK cells of the compounds obtained were performed. The structure-activity relationship analysis suggests that to possess virus-inhibiting activity, the compounds of this group should bear oxygen atom with a short linker (C2-C4), either as a hydroxyl group (18, 19, 29), keto-group (21) or as a part of a heterocycle (24). These compounds demonstrated low cytotoxicity along with high anti-viral activity.

Interaction of bis(trimethylsilyl)acetylene complex of titanocene with mercury trifluoroacetate

The reaction of the bis(trimethylsilyl)acetylene complex of titanocene Cp2Ti(Me3SiC2SiMe3) with mercury trifluoroacetate (NF3COO)2Hg at 20 °C in a THF medium affords titanocene bis(trifluoroacetate) Cp2Ti(OCOCF3)2 and metallic mercury. The structure of Cp2Ti(OCOCF3)2 was established by the analytical and spectroscopic methods and X-ray diffraction analysis.

Addition of CCl4 to unsaturated compounds catalyzed by M3(CO)12 (M=Fe, Ru, Os)

The addition of CCl4 to hex-1-ene and to the methyl ester ofN-(trans-cinnamoyl)-l-proline (2) catalyzed by M3(CO)12 or by the M3(CO)12+DMF system (M=Fe, Ru, Os) was studied. The use of ruthenium and osmium dodecacarbonyls in combination with DMF increases the yields of adducts CCl3CH2CHClC4H9 (4) and PhCHClCH(CCl3)C(O)R′ (3) over those obtained in reactions catalyzed by the same carbonyls without DMF. In addition to adduct3, salts [M(CO3)Cl3]−[Me2NH2]+ were isolated from the products of the reaction between CCl4 and1 in the presence of M3(CO)12+DMF (M=Ru, Os). These salts do not catalyze this reaction and apparently result from chain termination. Experimental results in favor of a coordination mechanism of the addition of CCl4 to olefins in the presence of Ru3(CO)12 and Os3(CO)12 were obtained.