Synthesis,structure, and rearrangements of new tricarbonylchromium complexes of substituted heptalenes

Reactions of 1,2,5,6,8,10-hexamethylheptalene (1) and its bond isomer, 1,4,5,6,8,10-hexamethylheptalene (2), with tricarbonylchromium complexes L{in3}Cr(CO){in3} (L=NH{in3} and Py) have been investigated. Thermodynamically less stable complex 1 exhibits higher reactivity with respect to Py{in3}Cr(CO){in3}/BF{in3} · Et{in2}O under the conditions of Öfele's reaction than complex2. At 10–30 °C, the Cr(CO){in3} group is coordinated to the asymmetrically substituted ring, which is accomplished by the shift of double bonds in the ligand, to afford tricarbonyl-[1,4,5,6,8,10-hexamethyl-{su6}-(10a, 1–5)heptalene]-chromium (6) as the only mononuclear complex. Under more drastic conditions (Raush's reaction, 80 °C),1 2 interconversion proceeds faster than the reaction of individual bond isomers with coordinatively unsaturated hot particles (solv){inn}Cr(CO){in3}. In this case, all of the four possible isomeric mononuclear complexes (6–9) and two binuclear complexes (10 and 11) are formed. The structures of complexes 6–11 have been studied by NMR and mass spectrometry, the structure of6 has been established by X-ray diffraction analysis. Heating a solution of6 in octane at 115 °C results in the isomerization of6 into complex7 through the intracycle 1,2-shift of the Cr(CO){in3} group and also in its conversion into complex8, which is the first example of interring {su6}{su6}-haptotropic rearrangement in nonplanar seven-membered -systems.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2220–2226, December, 1994.We would like to thank N. S. Kulikov for measuring mass spectra and L. A. Aslanov for helpful discussion of the results of X-ray diffraction analysis.The Research Group from the Moscow State University gratefully acknowledges the support of this work by the International Science Foundation (Grant No. MQ 5000) and the Russian Foundation for Basic Research (Project No. 94-03-08325).     

Ir(I) complexes with oxazoline-thioether ligands: nucleophilic attack of pyridine on coordinated 1,5-cyclooctadiene and application as catalysts in imine hydrogenation

Oxazoline-thioether ligands 6-11 react with [Ir(η⁴-COD)Py₂]PF₆ (COD=C₈H₁₂=1,5-cyclooctadiene) to give [Ir(σ-η²-C₈H₁₂Py⁺)L] PF₆ (L=oxazoline-thioether ligand) (12a-d) complexes resulted from the coordination of ligand to the metal and subsequent nucleophilic attack of pyridine to one of the double carbon bond of COD with concomitant iridium-carbon bond formation. When [Ir(η⁴-COD)₂]BF₄ was used as starting material, the reaction with ligands 7, 9 afforded the complexes [Ir(η⁴-COD)L]BF₄. Application of these iridium complexes to the reduction of N-(α-methyl)benzylidenbenzylamine gave low or negligible enantioselectivity.     

Transition metal complexes with heterocyclic analogs of fluorene. 1. Synthesis, structures, and haptotropic rearrangements of tricarbonylchromium complexes of dibenzothiophene

The complex formation of dibenzothiophene with chromium carbonyl complexes of the general formula L₃Cr(CO)₃ (L = Py, NH₃, or CO) afforded ⁶-C₁₂H₈SCr(CO)₃ (1). In the presence of tetramethylethylenediamine, complex 1 was selectively metallated with BuLi at position 4 of the coordinated ring to form ⁶-4-LiC₁₂H₈SCr(CO)₃ (2). In decane, the tricarbonylchromium group is reversibly and intramolecularly migrates from the unsubstituted to substituted ring due to the inter-ring haptotropic rearrangement (IRHR) at 130 °C for 100 h. In decane, the rate constant of IRHR was estimated experimentally by ¹H NMR spectroscopy and theoretically by the density functional theory (DFT).     

Synthesis and reactivity of dipropargylic disulfides: tandem rearrangements, cyclization, and oxidative dimerization

Synthesis and facile rearrangement and cyclization reaction of new dipropargylic disulfides are described. A possible mechanism for these transformations involving an initial double [2,3]-sigmatropic rearrangement to the elusive diallenyl disulfides via a thiosulfoxide intermediates is suggested.     

Synthesis, characterization, and catalytic activity of divalent organolanthanide complexes with new tetrahydro-2H-pyranyl-functionlized indenyl ligands

Two series of new divalent organolanthanide complexes with the general formula [η⁵:η¹-{1-R-3-(C₅H₉OCH₂)C₉H₅}]₂Ln^II (R = H, Ln = Yb (3); R = Me₃Si, Ln = Yb (4); R = H, Ln = Eu (5); R = Me₃Si, Ln = Eu (6)) were prepared by reactions of 2 equiv. of 1-R-3-(C₅H₉OCH₂)C₉H₆ (R = H (1), R = Me₃Si (2)) with the lanthanide(III) amides [(Me₃Si)₂N]₃Ln(μ-Cl)Li(THF)₃ (Ln = Yb, Eu) via a one-electron reductive elimination process. Recrystallization of 6 from n-hexane afforded [η⁵:η¹-(C₅H₉OCH₂C₉H₅SiMe₃)]₂Eu^II · (C₆H₁₄)_0.5 (7). All compounds were fully characterized by elemental analyses, and spectroscopic methods. The structures of complexes 4 and 7 were additionally determined by single-crystal X-ray analyses. The catalytic activity of the complexes on methyl methacrylate and ε-caprolactone polymerization was studied, and the temperatures, substituents on the indenyl ring, and solvents effects on the catalytic activity of the complexes were examined.     

Synthesis,characterizations and crystal structures of new antimony (III) complexes with dithiocarbamate ligands

Eight new antimony (III) complexes containing dithiocarbamate ligands (R₂NCS₂)₂SbBr [R₂NCS₂ = OC₄H₈NCS₂ (1), C₂H₅NC₄H₈NCS₂ (2), Me₂NCS₂ (3), C₄H₈NCS₂ (4)] and (R₂NCS₂)₃Sb[R₂NCS₂ = C₅H₁₀NCS₂ (5), Bz₂NCS₂ (6), Et₂NCS₂ (7), (HOCH₂CH₂)₂NCS₂ (8)] have been synthesized by the reactions of antimony (III) halides with dithiocarbamate ligands in 1:2 or 1:3 stoichiometries. All the complexes have been characterized by elemental analysis, melting point as well as spectral [IR and NMR (¹H and ¹³C)] studies. The crystal structures of complexes 1, 5 and 8 have been determined by X-ray single crystal diffraction, and their electrochemical character has also been studied.     

Three copper(II) complexes of thiophene-2,5-dicarboxylic acid with dissimilar ligands: Synthesis, IR and UV–Vis spectra, thermal properties and structural characterizations

Three thiophene-2,5-dicarboxylic acid (H₂tdc) complexes of copper(II) with 2-aminomethylpyridine (ampy), {[Cu₂(μ-tdc)₂(ampy)₂]·2DMF}_n (1), ethylenediamine (en), trans-[Cu(H₂O)₂(en)₂](tdc) (2) and 4-methylimidazole (4-meim), trans-[Cu(H₂O)₂(4-meim)₄](tdc)·4H₂O (3) have been synthesized and characterized by spectral (IR, UV–Vis), thermal analyses and X-ray diffraction techniques. In 1, thiophene-2,5-dicarboxylate acts as a bridging bis(bidentate) ligand through four carboxylate oxygen atoms forming a 1-D zigzag polymeric chain, whereas in 2 and 3 the tdc dianion behaves as a counter ion. In all cases, the Cu(II) centers have an octahedral coordination geometry. Three-dimensional frameworks are constructed though hydrogen bonding and/or C–H···π interactions in the three complexes.     

Synthesis, characterization, reactivity and computational studies of new rhenium(I) complexes with thiosemicarbazone ligands derived from 4-(methylthio)benzaldehyde

N-thioamide thiosemicarbazone derived from 4-(methylthio)benzaldehyde (R = H, HL¹; R = Me, HL² and R = Ph, HL³) have been prepared and their reaction with fac-[ReX(CO)₃(CH₃CN)₂] (X = Br, Cl) in methanol gave the adducts [ReX(CO)₃(HLⁿ)] (1a X = Cl, n = 1; 1a′ X = Br, n = 1; 1b X = Cl, n = 2; 1b′ X = Br, n = 2; 1c X = Cl, n = 3; 1c′ X = Br, n = 3) in good yield.All the compounds have been characterized by elemental analysis, mass spectrometry (ESI), IR and ¹H NMR spectroscopic methods. Moreover, the structures of HL², HL³, HL³·(CH₃)₂SO and 1b′·H₂O were also elucidated by X-ray diffraction. In 1b′, the rhenium atom is coordinated by the sulphur and the azomethine nitrogen atoms (κS,N³) forming a five-membered chelate ring, as well as three carbonyl and bromide ligands. The resulting coordination polyhedron can be described as a distorted octahedron.The structure of the dimers is based on rhenium(I) thiosemicarbazonates [Re₂(L¹)₂(CO)₆] (2a), [Re₂(L²)₂(CO)₆] (2b) and [Re₂(L³)₂(CO)₆] (2c) as determined by X-ray studies. Methods of synthesis were optimized to obtain amounts of these thiosemicarbazonate complexes. In these compounds the dimer structures are achieved by Re-S-Re bridges, where S is the thiolate sulphur from a κS,N³-bidentate thiosemicarbazonate ligand.Some single crystals isolated in the synthesis of 2b contain [Re(L⁴)(L²)(CO)₃] (3b) where L⁴ (=2-methylamine-5-(para-methylsulfanephenyl)-1,3,4-thiadiazole) is originated in a cyclization process of the thiosemicarbazone. Furthermore, the rhenium atom is coordinate by the sulphur and the thioamidic nitrogen of the thiosemicarbazonate (κS,N²) affording a four-membered chelate ring.     

Synthesis, characterizations and crystal structures of new organoantimony(V) complexes with various isomers of fluoromethylbenzoate ligands

Six new organoantimony(V) complexes containing various isomers of fluoromethylbenzoate ligands [RC₆H₃COO]₂SbPh₃ and [RC₆H₃COO]SbPh₄ [R = 3-F-4-(CH₃) (1, 4), 4-F-2-(CH₃) (2, 5), 5-F-2-(CH₃) (3, 6)] have been synthesized by the reactions of triphenylantimony(V) dichloride or tetraphenylantimony(V) bromide with various isomers of fluoromethylbenzoate ligands in 1:2 or 1:1 stoichiometries. All the complexes have been characterized by elemental analysis, IR and NMR [¹H, ¹³C and ¹⁹F] studies. The crystal structures of complexes 1, 3, 4, 5 and 6 have been determined by X-ray single crystal diffraction. The structure of complexes show that the five-coordinated antimony(V) atom adopts a distorted trigonal bipyramidal geometry. Furthermore, weak but significant intermolecular C–H···O, C–H···F hydrogen bonds, C–H···pi stacking lead to aggregation and assembly of these complexes into 1D and 2D supramolecular frameworks.     

Synthesis of 3-isocyano-nido-7,8-dicarbaundecaborate salts and their use as new isonitrile ligands in transition-metal complexes

The treatment of 3-isocyano-o-carboranes with an alkali solution in alcohol results in the regioselective splitting out of a boron atom from position 6 of theo-carborane nucleus to give 3-isocyano-nido-7,8-dicarbaundecaborate salts, in which the isonitrile group is attached to the boron atom of thenido-polyhedron anion. 3-Isocyano-nido-7,8-dicarbaundecaborate salts are new isonitrile ligands in transition-metal complexes. Complexes with chromium, molybdenum, tungsten, and iron compounds have been obtained.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1458–1460, August, 1993.     

Palladium complexes of multidentate pyrazolylmethyl pyridine ligands: Synthesis,structures and phenylacetylene polymerization

The compounds, 2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)pyridine (_MeNˆNˆN) (L1) and 2,6-bis(3,5-ditertbutylpyrazol-1-ylmethyl)pyridine (_tBuNˆNˆN) (L2), react with either [Pd(NCMe)₂Cl₂] or [Pd(COD)ClMe] to form the mononuclear palladium complexes [Pd(_MeNˆNˆN)Cl₂] (1), [Pd(_MeNˆNˆN)ClMe] (2), [Pd(_tBuNˆNˆN)Cl₂] (3) and [Pd(_tBuNˆNˆN)ClMe] (4). Reactions of 1, 2 and 4 with the halide abstractor, NaBAr₄ (Ar = 3,5-(CF₃)₂C₆H₃), led to the formation of stable tridentate cationic species [Pd(_MeNˆNˆN)Cl]⁺(5), [Pd(_MeNˆNˆN)Me]⁺ (6) and [Pd(_tBuNˆNˆN)Cl]⁺ (7) respectively. The analogous carbonyl linker cationic species [Pd{(3,5-Me₂pz-CO)₂-py}Cl]⁺ (9) and [Pd{(3,5-^tBu₂pz-CO)₂-py}Cl]⁺ (10), prepared by halide abstraction of the neutral complexes [Pd{(3,5-Me₂pz-CO)₂-py}Cl₂] and [Pd{(3,5-^tBu₂pz-CO)₂-py}Cl₂] by NaBAr₄, were however less stable with t_1/2 of 14 and 2 days respectively. Attempts to crystallize 1 and 3 from the mother liquor resulted in the isolation of the salts [Pd(_MeNˆNˆN)Cl]₂[Pd₂Cl₆] (11) and [Pd(_tBuNˆNˆN)Cl]₂[Pd₂Cl₆] (12). Although when complexes 1–4 were reacted with modified methylaluminoxane (MMAO) or NaBAr₄, no active catalysts for ethylene oligomerization or polymerization were formed, activation with silver triflate (AgOTf) produced active catalysts that oligomerized and polymerized phenylacetylene to a mixture of cis-transoidal and trans-cisoidal polyphenylacetylene.     

Synthesis,anticancer and antimicrobial evaluation of new pyridyl and thiazolyl clubbed hydrazone scaffolds

Abstract

A series of new hydrazones bearing pyridyl and thiazolyl scaffolds have been synthesized and evaluated for their in vitro anticancer and antimicrobial activities. The anticancer activity was evaluated against the A549 lung cancer cell line. The eight hydrazone derivatives have shown better anticancer activity than positive control doxorubicin against the A549 lung cancer cell line. The antimicrobial activity was evaluated against bacterial and fungal pathogens by using well diffusion method. The four hydrazone derivatives have displayed good antimicrobial activities. Molecular docking studies of the synthesized hydrazone derivatives revealed good binding via hydrogen bond interactions with key residues on active sites as well as neighboring residues with an active site of Focal adhesion kinase (PDB ID 2JKO). A computational study for the prediction of absorption, distribution, metabolism, and excretion (ADME) properties of all compounds has also been performed.     

Synthesis of chiral polydentate ligands and the use of their titanium complexes as pre-catalysts for the asymmetric trimethylsilylcyanation of benzaldehyde

A number of polydentate ligands based on enantiomerically pure binaphthol have been synthesized. The ligand complexes with titanium isopropoxide were used as catalysts for the asymmetric addition of trimethylsilyl cyanide to benzaldehyde. A fragment with axial chirality is responsible for the configuration of O-trimethylsilyl cyanohydrin product. In the case of the optimum ligand based on (R)-binaphthol and (S)-leucinol, an enantiomeric excess of 86% and quantitative yield were achieved in 4 h. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1946–1953, September, 2008.     

(-)-Menthol as a source of new N,N-diamine ligands for asymmetric transfer hydrogenation

The synthesis of new chiral N-monotosylated-1,2-diamines based on the (-)-menthol skeleton is presented. The elimination of HCl from neomenthyl chloride obtained from an Appel reaction led to p-menth-3-ene in excellent yield. Further functionalization of the double bond in p-menth-3-ene with chloramine-T gave the corresponding N-tosylaziridines, which upon reaction with sodium azide and subsequent reduction of the azide functional group, formed the 1,2-diamine system. The synthesized chiral ligands proved effective in the asymmetric transfer hydrogenation of aromatic ketones and an endocyclic imine.     

Synthesis, resolution and racemisation studies of new tridentate ligands for asymmetric catalysis

A method for the high-yielding preparation of two tridentate, isoquinoline-derived ligands, involving successive Suzuki cross-coupling reactions, is described. The first ligand could be resolved via molecular complexation with N-benzylcinchonidinium chloride, while the second was resolved by chromatographic separation of its epimeric camphorsulfonates. The barrier to rotation about the central biaryl axis was evaluated via racemisation studies, and the absolute configuration assigned by X-ray crystallography.     

Nitrile ligands for controlled synthesis of alkynyl-ruthenium based homo and hetero bimetallic systems

Wire like mono- and poly-nuclear molecules based on alkynyl ruthenium complexes whose core unit is trans-[Ru(CC-R)(R′CN)(dppe)₂][PF₆] are readily formed in soft conditions. The electronic dual character of the metallic unit, donor through the acetylide moiety, acceptor versus the nitrile ligand is exemplified through electrochemical studies of a series of ethynylferrocene and cyanoferrocene derivatives. A single crystal X-ray diffraction analysis of the [(dppe)₂(PhCC)Ru(NC-C₆H₄-CN)Ru(CCPh)(dppe)₂][2PF₆] bimetallic complex 5 shows that the global structure of such complexes consists of wire type dimetallic units. With the availability of this versatile, direct, and simple route, a new class of extended rigid rod systems of nanometric size with multilevel electron transfers is readily accessed.     

Synthesis,characterization and molecular docking of new C,N‐palladacycles containing pyridinium‐derived ligands: DNA and BSA interaction studies and evaluation as anti‐tumor agents

Four new monomeric Pd (II) complexes with formulas [Pd(C,N)‐(2′‐NH₂C₆H₄)C₆H₄ (N₃)(L)] ( A ), ( B ) and [Pd(C,N)‐C₆H₄CH₂NH(C₄H₉)(N₃)(L)] ( C ), ( D ), [L = isonicotinamide for ( A ) and ( C ), L = 4‐N,N‐dimethylaminopyridine for ( B ) and ( D )] have been synthesized using four initial dimers [Pd₂{(C,N)‐(2′‐NH₂C₆H₄)C₆H₄}₂(μ‐OAc)₂] ( 1 ), [Pd₂{(C,N)‐ (2′‐NH₂C₆H₄)C₆H₄}₂(μ‐N₃)₂] ( 3 ) for A and C , and [Pd₂{(C,N)‐C₆H₄CH₂NH(C₄H₉)}₂(μ‐OAc)₂] ( 2 ) and [Pd₂{(C,N)‐C₆H₄CH₂NH(C₄H₉)}₂(μ‐N₃)₂] ( 4 ) for B and D . Then synthesized complexes have been characterized by Fourier transform‐infrared, NMR spectroscopy and thermal gravimetric‐differential thermal analysis. Furthermore, UV–Vis spectroscopy, fluorescence spectroscopy, circular dichroism (CD) and helix melting temperature measurements have been employed to study the binding interaction of them with calf thymus‐deoxyribonucleic acid (DNA). The results reveal that all synthesized complexes can interact with DNA via groove‐binding mode. Bovine serum albumin (BSA)‐binding studies have been carried out using UV–Vis spectroscopy, emission titration and CD. However, competitive binding studies using warfarin, ibuprofen and digoxin on site markers demonstrated that the complexes bind to different sites on BSA. The results also indicated that the binding site was mainly located within site‐III for complex A , and site‐I for complexes B , C and D of BSA. In addition, molecular docking studies have been executed to determine the binding site of the DNA and BSA with complexes. Eventually, in vitro cytotoxicity of synthesized palladium complexes and cisplatin were carried out against human promyelocytic leukemia cancer (Hela) and breast cancer (MCF‐7) cell lines. Pursuant to the IC₅₀ values, the cytotoxicity of complexes against MCF‐7 was more than Hela.     

Synthesis, characterization and spectroscopic properties of 1,2-diiminetricarbonylrhenium(I)chloride complexes with o-benzoquinone diimines as ligands

The novel organometallic complexes Re(BQDI---R)(CO)₃Cl with BQDI---R=4,5-substituted o-benzoquinone diimines (R=H, Me, OMe, Cl) have been prepared and characterized by elemental analysis, IR, MS and ¹H-NMR spectroscopic methods. Their electronic spectra display a long-wavelength absorption band which can be ascribed to a metal-to-ligand charge transfer (MLCT) transition from Re(I) to the low-lying π*-orbitals of the o-benzoquinone diimine ligand, even though a significant degree of metal–ligand orbital mixing is occurring. The energy of this absorption band correlates very well with the nature of the substituents R in the 4,5-position of BQDI---R. In solvent series of decreasing polarity, the MLCT absorption maximum is shifted to longer wavelengths (negative solvatochromism). None of the Re(BQDI---R)(CO)₃Cl complexes studied is photoluminescent at 298 or 77 K.     

Synthesis,molecular modeling,TD-DFT,antimicrobial, and in vitro therapeutic activity of new spherical nano-sized sulfonamide imine ligands and their zinc (II) and copper (II) complexes

A series of nanometer-sized spherical sulfonamide imine ligands HL ¹ -HL ⁵ and their copper and zinc complexes were synthesized and fully characterized based on elemental analyses, spectroscopic (UV/vis, FT-IR, NMR, EPR, SEM) studies, molar conductance and thermal analyses. Furthermore, computational studies of HL ¹ -HL ⁵ were carried out by the DFT/B3LYP method. TD-DFT, HOMO and LUMO energy values, chemical hardness, electronegativity, electrophilic index, softness, and other parameters were calculated. Screening against several pathogenic microorganisms indicated that HL ¹ exhibited high activity against the tested Gram-negative bacteria relative to other analogues and the inhibition activity is greater than the standard Gentamicin. Analogously, HL ² exhibited high potent activity against the tested Gram-positive bacteria. Copper complexes exhibited a higher potent activity than zinc analogues. Noteworthy, inhibition activity of [Cu ( L ³ )(OAc)] complex is higher than that of the standard Ampicillin. [Cu ( L ² )(OAc)] complex displayed a similar activity of the standard bactericides and fungicides in use. The complexes showed appreciated values of MIC against bacterial strains: B. subtilis (MIC = 0.4 μg / mL), E. coli and S. pneumonia (MIC = 1.95 μg / mL) and P. aeruginosa (MIC = 7.81 μg / mL). in vitro cytotoxic activities study proved that [Cu ( L ³ )(OAc)] complex exhibited appreciable activity versus (HEPG-2); IC₅₀ = 4.8 μg/ml, while [Cu( L ² )(OAc)] complex showed a high activity against (MCF-7); IC₅₀ = 6.2 μg/ml. These results could be considered as new findings of promising antitumor candidates for experimental chemotherapy.     

Synthesis,characterization, crystal structure and thermal analysis of a copper(II) mononuclear compound with 2,6- bis (3,5-dimethyl- N -pyrazolyl)pyridine (bdmpp) and selenocyanate as ligands

A single crystal of the copper(II) compound, [Cu(bdmpp)(SeCN)₂], 2, was obtained and its crystal structure was determined by X-ray diffraction methods. The complex was characterized by elemental, thermal and FTIR analysis. The FTIR analysis of the complex clearly shows the SeCN peaks at 2096 and 2061?cm^?1 which did not exist in the free organic ligand (bdmpp). X-ray analysis showed that 2 crystallized in the monoclinic space group P2₁/c. Cu(II) has a distorted trigonal bipyramidal coordination involving three N atoms from the ligand and two N atoms from the selenocyanate group.