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Transition Metal Chemistry

Current research reports and chronological list of recent articles..




Transition Metal Chemistry is an international scientific journal dealing with all aspects of the preparation of transition metal-based compounds of all kinds, their structural, physical, kinetic and biological properties, their use in chemical synthesis as well as their application in the widest context, their role in naturally occurring systems and more.

The publisher is Springer. The copyright and publishing rights of specialized products listed below are in this publishing house. This is also responsible for the content shown.

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Additional research articles see Current Chemistry Research Articles:

 - Organometallics.



Transition Metal Chemistry - Abstracts



Synthesis, characterization and magnetic properties of cobalt(II) and manganese(II) metal–organic frameworks assembled from 4,6-bis(imidazol-1-yl)isophthalic acid ligands

Abstract

Two metal–organic frameworks of 4,6-bis(imidazol-1-yl)isophthalic acid (H2biip), of general formula, {[M2(biip)2(H2O)]·EtOH2}n (M = Co (1), Mn (2)), have been synthesized under solvothermal conditions. Complexes 1 and 2 are isomorphic and exhibit three-dimensional metal–organic frameworks with a 2-nodal (4,8)-connected topological network, Point Symbol {416.612}{44.62}2. The magnetic properties of the complexes were examined, indicating antiferromagnetic interactions between the metal centers in the temperature range from 2 to 300 K.


Datum: 23.05.2018


Anti-Markovnikov hydroaminations of styrene catalyzed by palladium(II) N-heterocyclic carbene complexes under conventional and microwave heating

Abstract

Six palladium(II) complexes with benzimidazole-based N-heterocyclic carbene ligands were synthesized by transmetallation reactions between silver(I) N-heterocyclic carbene complexes and PdCl2(PhCN)2. The complexes were characterized by physicochemical and spectroscopic methods. The palladium complexes were tested as catalysts for intermolecular hydroamination reactions of styrene with various anilines in ionic liquids under both conventional and microwave heating. All of these complexes proved to be catalytically active in these reactions. The anti-Markovnikov addition products were selectively obtained by using 1 mol% of the palladium complex.


Datum: 23.05.2018


A manganese Schiff base complex immobilized on copper–ferrite magnetic nanoparticles as an efficient and recyclable nanocatalyst for selective oxidation of alcohols

Abstract

A magnetically recoverable nanocatalyst was synthesized by covalent binding of a Schiff base ligand, namely N,N′-bis(Salicylidene)-1,3-diaminopropane-2-ol (H2salpn), onto the surface of silica-coated magnetic CuFe2O4 nanoparticles, followed by complexation with MnCl2. The resulting core–shell nanoparticles were characterized by spectroscopic and microscopic methods, including FTIR, XRD, VSM, TGA elemental analysis, TEM, and SEM. The Mn content was determined by ICP analysis. The nanoparticles were investigated as a catalyst for the selective oxidation of alcohols to the corresponding carbonyl compounds with tertiary-butyl hydrogen peroxide. The catalyst can be magnetically separated for reuse, with no noticeable loss of activity in subsequent reaction cycles. FTIR, VSM, and leaching experiments after three successive cycles confirmed that the catalyst was strongly anchored to the magnetic nanoparticles. A suitable mechanism for the reaction is proposed.


Datum: 10.05.2018


Synthesis, crystal structures and fluorescence properties of coordination polymers based on tetrahedral ligands and secondary bidentate linkers

Abstract

Two coordination polymers, namely {[Co2L(dpe)2]·0.42H2O} (1), and {[Zn4L2(dpe)4]·4H2O} (2), were solvothermally prepared from a flexible tetrapodal ligand tetrakis[(3-carboxyphenyl)oxamethyl]methane acid (H4L) and a secondary bidentate linker (E)-1,2-di(pyridin-4-yl)ethane (dpe). Single-crystal X-ray diffraction analysis revealed that these compounds possess similar three-dimensional structures, in which the frameworks are constructed from dinuclear SBUs (secondary building units) [M2(COOR)4N4] (M = Co or Zn) and tetrahedral L4− linkers. The overall structures of both compounds can be described as (4, 6)-connected binodal networks, with a Schläfli symbol of {42537}{4255647282} according to the topological analysis. Compound 2 exhibits strong photoluminescence at room temperature, with a peak at 422 nm (excitation at 370 nm), most probably from an intraligand and/or ligand-to-ligand charge transfer (LLCT). The emission of compound 2 was quenched efficiently by Fe3+ ion, suggesting that 2 could be used as a fluorescence sensor for Fe3+.


Datum: 09.05.2018


Bis-chelates of nickel(II) and copper(II) with an O,S-donor piperazine ligand

Abstract

A bidentate O,S-donor ligand N-(4-benzoyl-piperazine-1-carbothioyl)-benzamide (HL) was synthesized from the reaction of in situ generated benzoylisothiocyanate with piperazine and benzoyl chloride. Reaction of HL with the perchlorate salts of NiII and CuII in DMF–MeOH mixture using NEt3 as base afforded complexes 1 and 2 as crystalline solids in moderate yields. Physico-chemical and spectroscopic studies confirmed the chemical compositions of both the free ligand and its M(O,S)2 type metal complexes. The ligand undergoes keto-thione to keto-thiol tautomerization during metalation which is the driving force for the formation of neutral bis-chelates. The X-ray crystal structure of complex 2 shows bis-chelation with a cis-conformation in an overall square planar environment.

Graphical abstract

M(O,S)2 complexes have been stabilized in cis-conformation from a piperazine based thiourea ligand through keto-imine-thiol tautomerization.


Datum: 09.05.2018


Microwave-assisted synthesis of 3-substituted-6-ferrocene methylene-1,2,4-triazolo[3,4- b ]-1,3,4-thiadiazoles

Abstract

A series of triazolo-thiadiazole derivatives containing ferrocene were synthesized under microwave assistance. Compared with the phosphorus oxychloride method, the microwave method has the advantages of simple operation, short reaction time, fast reaction rate and high yield. The effects of different reaction conditions were explored, and under the optimized conditions, the products were obtained in good yields (up to 80%).


Datum: 04.05.2018


Kinetics and mechanism of pyridine substitution from [(η 3 -C 3 H 5 )Mo(CO) 2 (X)(py) 2 ] (X = Cl, Br; py = pyridine) by 1,2-bis(diphenylphosphino)ethane

Abstract

Reactions of [(η3-C3H5)Mo(CO)2(X)(py)2] (X = Cl (1), Br (2); py = pyridine) with 1,2-bis(diphenylphosphino)ethane (= dppe) in toluene solution resulted in replacement of the py ligands and the formation of [(η3-C3H5)Mo(CO)2(X)(κ2-P,-dppe)]. Thermal kinetics of these substitution reactions, under pseudo-first-order reaction conditions, indicated that these reactions proceed by a rate law that is first order in the concentration of the metal complex and zero order in dppe concentration. The data suggest a two-step substitution process. The first step is slow and reversible, involving the dissociation of the first py coligand to form a coordinatively unsaturated [(η3-C3H5)Mo(CO)2(X)(py)] transient species. This is followed by an irreversible end-on coordination of the dppe ligand at the transient species to give [(η3-C3H5)Mo(CO)2(X)(py)(κ1-P-dppe)] as an intermediate. The latter complex undergoes a fast and entropy-driven ring closure, resulting in the substitution of the second py ligand to give [(η3-C3H5)Mo(CO)2(X)(κ2-P,-dppe)]. Rate constants and activation parameters for these reactions have been determined and discussed. Competition studies for the [(η3-C3H5)Mo(CO)2(X)(py)] intermediates show that these transients are highly reactive and react almost indiscriminately with both py and dppe.

Graphical Abstract

Reactions of [(η3-C3H5)Mo(CO)2(X)(py)2] (X = Cl, Br; py = pyridine) with dppe give [(η3-C3H5)Mo(CO)2(X)(κ2-P,-dppe)]. Thermal kinetics of these substitution reactions, under pseudo-first-order reaction conditions, indicate that these reactions proceed by a rate law that is first order in the concentration of the metal complex and zero order in dppe concentration. A mechanism is proposed and suggests initial replacement of py, followed by attack of one P-atom of dppe at [(η3-C3H5)Mo(CO)2(X)(py)] to give [(η3-C3H5)Mo(CO)2(X)(py)(κ1-P-dppe)] which losses another py to give [(η3-C3H5)Mo(CO)2(X)(κ2-P,-dppe)]. Rate constants and activation parameters for these reactions have been determined and discussed. Competition studies for the [(η3-C3H5)Mo(CO)2(X)(py)] intermediates show that these transients are highly reactive and react almost indiscriminately with both py and dppe.


Datum: 03.05.2018


Nitrile functionalized silver(I) N -heterocyclic carbene complexes: DFT calculations and antitumor studies

Abstract

A series of aliphatic nitrile functionalized benzimidazolium salts and their respective mononuclear N-heterocyclic carbene Ag(I)-NHC complexes are reported. The benzimidazolium salts were synthesized by N-alkylation of 1H-benzimidazole with an appropriate alkyl bromide, followed by reaction with either 5-bromovaleronitrile or 6-bromohexanenitrile. The respective mononuclear Ag(I)-NHC complexes were prepared by the reaction of the benzimidazolium salts with Ag2O. All the synthesized compounds were characterized by physico-chemical and spectroscopic techniques. The molecular structures of the two complexes were elucidated through single-crystal X-ray diffraction analyses. Density functional theory was used to model the structures of the other complexes. The benzimidazolium salts and their complexes were screened for cytotoxicity against a breast cancer cell line (MCF-7), using the MTT assay. All the Ag(I)-NHC complexes gave IC50 values ranging from 7.0 ± 1.06 to 12.9 ± 1.55 µM which are comparable to the standard drug, tamoxifen (IC50 = 11.2 ± 1.84 µM), while all of the benzimidazolium salts proved to be inactive.


Datum: 01.05.2018


A green synthesis of biaryls in water catalyzed by palladium nanoparticles immobilized on N -amidinoglycine-functionalized iron oxide nanoparticles

Abstract

Fe3O4 nanoparticles were prepared by co-precipitation and coated with SiO2 following the Stöber process. N-Amidinoglycine amino acid was then covalently connected to provide an excellent ligand for the immobilization of Pd nanoparticles. The resulting material was characterized by FE-SEM, TEM, EDX, XRD, VSM and ICP-AES analysis. The Fe3O4@SiO2@N-amidinoglycine@Pd0 proved to be a highly active catalyst for the Suzuki coupling reactions of various aryl halides with substituted phenylboronic acids in water, giving the desired products in excellent yields for short reaction times. Moreover, this catalyst can be easily recovered by using an external magnet and directly reused for several times without significant loss of activity.


Datum: 01.05.2018


Tuning the regioselectivity of (benzimidazolylmethyl)amine palladium(II) complexes in the methoxycarbonylation of hexenes and octenes

Abstract

Reactions of N-(1H-benzoimidazol-2-ylmethyl-2-methoxy)aniline (L1) and N-(1H-benzoimidazol-2-ylmethyl-2-bromo)aniline (L2) with p-TsOH, Pd(AOc)2 and two equivalents of PPh3 or PCy3 produced the corresponding palladium complexes, [Pd(L1)(OTs)(PPh3)] (1), [Pd(L2)(OTs)(PPh3)] (2) and [Pd(L1)(OTs)(PCy3)] (3), respectively, in good yields. The new palladium complexes 13 and the previously reported complexes [Pd(L1)ClMe] (4) and [Pd(L2)ClMe] (5) gave active catalysts in the methoxycarbonylation of terminal and internal olefins to produce branched and linear esters. The effects of complex structure, nature of phosphine derivative, acid promoter and alkene substrate on the catalytic activities and selectivity have been studied and are herein reported.


Datum: 01.05.2018


Organophosphines in PtPCOX (X = N, Cl, S), PtPCNX (X = Cl, S, Br, I, As) and PtPCClX (X = S, I, As) derivatives: structural aspects

Abstract

In this review are classified and analyzed structural parameters of almost 90 monomeric organoplatinum complexes with inner coordination spheres consisting of PtPCOX (X = N, Cl, S), PtPCNX (X = Cl, S, Br, I, As) and PtPCClX (X = S, I, As). These complexes crystallized in three crystal systems: orthorhombic (× 11), triclinic (× 32) and monoclinic (× 45). Distorted square planar arrangements about the Pt(II) atoms are provided by mono-, heterobi- and heterotridentate donor ligands. The chelating ligands create a wide variety of four-, five- and six-membered metallocyclic rings and the effects of both steric and electronic factors influence the L–Pt–L bite angles. There are wide variations in the trans-positions of the donor ligands. Two examples are classified as distortion isomers.


Datum: 01.05.2018


Syntheses, structures, and catalytic activity in Friedel–Crafts acylations of substituted tetramethylcyclopentadienyl molybdenum carbonyl complexes

Abstract

Reactions of the substituted tetramethylcyclopentadienes [C5HMe4R] [R = t Bu, Ph, CH2CH2C(CH3)3] with Mo(CO)3(CH3CN)3 in refluxing xylene gave a series of dinuclear molybdenum carbonyl complexes [(η5-C5Me4R)Mo(CO)3]2 [R = t Bu (1), Ph (2), CH2CH2C(CH3)3 (3)], [(η5-C5Met Bu)Mo(μ-CO)2]2 (4)], and [(η5-C5Me4)t Bu]2Mo2O4(μ-O) (5)], respectively. Complexes 15 were characterized by elemental analysis, IR, 1H NMR, and 13C NMR spectroscopy. In addition, their crystal structures were determined by X-ray crystal diffraction analysis. The catalytic activities of complexes 13 in Friedel–Crafts acylation in the presence of o-chloranil has also been investigated; the reactions were achieved under mild conditions to give the corresponding products in moderate yields.


Datum: 01.05.2018


Dinuclear NHC–palladium(II) complexes: synthesis,characterization and application to Suzuki–Miyaura cross-coupling reactions

Abstract

Four dinuclear N-heterocyclic carbene–palladium(II) complexes 14 were prepared and characterized by elemental analysis and spectroscopic methods. The X-ray crystal structure of complex 2 showed a dinuclear framework in which N-heterocyclic ligands bridge between two square planar palladium(II) units. Each palladium center is surrounded by an imidazolylidene, a nitrogen atom from the central linking ligand, and two trans-chloride ligands. These dinuclear NHC–palladium(II) complexes exhibited efficient catalytic activities for the Suzuki–Miyaura coupling of aryl and benzyl chlorides with arylboronic acids.

Graphical Abstract


Datum: 01.05.2018


Complexation of hydroxamate-based siderophores with cobalt(II/III): growth inhibitory effect of cobalt(III)-desferricoprogen complex on fungi

Abstract

Solution equilibrium results for Co(II) and Co(III) complexes of two natural hydroxamate-based siderophores, the exocyclic desferricrocin (DFR) and the endocyclic triacetylfusarinine (TAF) are presented. The three hydroxamate chelating functions of TAF were found to complete the octahedral coordination sphere of a Co(II) ion in stepwise processes, but following the coordination of two hydroxamates of DFR practically in one step, the third function, most probably because of sterical reasons, remained uncoordinated. A comparison with corresponding results for the previously studied acyclic desferrioxamine B (DFB) and desferricoprogen (DFC) provided some information about the effects of the molecular framework of siderophores on their cobalt-binding ability. The oxidation of the central metal ion under basic conditions and investigation of the cobalt(III) complexes by cyclic voltammetry were also made. Compared to Fe(III), by several orders of magnitude, higher stability complexes were formed with Co(III). The possibility of any effect of the Co(III)-siderophore complex on microbial Fe(III) uptake was tested by investigation of the antifungal effect of Co(III)-DFC in comparison with that of CoCl2 on two fungi cultures, Penicillium brevicompactum and Aspergillus fumigatus.


Datum: 01.05.2018


Kinetics and mechanism of interactions of some monofunctional Au(III) complexes with sulphur nucleophiles

Abstract

Kinetics of the substitution reactions between monofunctional Au(III) complexes, [Au(dien)Cl]2+, [Au(bpma)Cl]2+ and [Au(terpy)Cl]2+ (dien = 3-azapentane-1,5-diamine, bpma = di-(2-picolyl) amine, terpy = 2,2′;6′,2″-terpyridine), and biologically relevant sulphur ligands, namely glutathione (GSH), l-methionine (l-Met) and l-cysteine (l-Cys), were studied in 0.1 M HCl (pH = 1.0). The reactions were followed under pseudo-first-order conditions as a function of ligand concentration and temperature using stopped-flow spectrophotometry. The [Au(terpy)Cl]2+ complex proved to be more reactive than the [Au(bpma)Cl]2+ and [Au(dien)Cl]2+ complexes. The reactivities of the nucleophiles follow the same order for all three complexes, viz. l-Met > GSH > l-Cys. Values of the activation parameters of the reactions support an associative substitution mechanism. In order to confirm that these monofunctional Au(III) complexes undergo a single substitution process in strongly acidic medium, the reaction between [Au(terpy)Cl]2+ and l-Met was studied by HPLC. At pH = 1.0, only one reaction product was detected.


Datum: 01.05.2018


Preparation, characterization and crystal structures of metal(II) tetraza macrocyclic complexes with organic co-ligands

Abstract

The complexes [Ni(L1)(pyc)2]·2H2O (1) (L1 = C-meso-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane; Hpyc = pyrazinecarboxylic acid) and [Cu(L2)(H-cpdc)] (2) (L2 = 3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,01.18,07.12]docosane; H2-cpdc = cyclopropanedicarboxylic acid) have been synthesized and structurally characterized. The crystal structure of complex 1 shows a distorted octahedral coordination geometry around the nickel(II) center, with four secondary amines in the equatorial positions and two nitrogen atoms of the pyc ligands in the trans positions. In complex 2, the coordination environment around the copper(II) center is a Jahn–Teller distorted octahedron with four Cu–N bonds and two axial Cu–O bonds. The electronic spectra, electrochemical and TGA behavior of the complexes are significantly affected by the nature of the axial pyc and H-cpdc ligands.


Datum: 01.05.2018


A dinuclear ruthenium(II) complex as an inducer and potential luminescent switch-on probe for G-quadruplex DNA

Abstract

Given that recognition and regulation of G-quadruplex nucleic acid structures is an important goal for the development of chemical tools and medicinal agents, a dinuclear ruthenium complex [Ru2(bpy)4(bip-phenol)](ClO4)4 {bpy = 2,2′-bipyridine, bip-phenol = 2,4-bis(1H-imidazo[4,5-f] [1,10] phenanthroline-2-yl)phenol} has been synthesized and characterized, and its interactions with telomeric G-quadruplex DNA have been explored by photophysical and biophysical methods. This complex can induce and stabilize the formation of an antiparallel G-quadruplex of telomeric DNA in the absence of salt, or in the presence of K+/Na+-containing buffer. The complex binds strongly to the telomeric G-quadruplex, with a binding constant Kb > 106 and a 2:1 [complex]/[quadruplex] binding ratio. Fluorescence titrations revealed that the complex behaves as a promising photophysical “light switch” for G-quadruplex DNA, with 8.6- and 8.4-fold fluorescence enhancements in Na+ and K+ buffers, respectively.


Datum: 30.04.2018


Crystal structures and spectroscopic properties of copper(II)–dipicolinate complexes with benzimidazole ligands

Abstract

The syntheses, crystal structures and spectroscopic properties of three Cu(II)–dipicolinate complexes with benzimidazole ligands, namely [Cu(bzim)(dipic)(MeOH)] (1), [Cu2(2-Etbzim)2(dipic)2]n ·0.5nH2O (2) and [Cu2(2-iPrbzim)2(dipic)2]n (3), where dipic = dipicolinate, bzim = 1-H-benzimidazole, 2-Etbzim = 2-ethyl-1-H-benzimidazole and 2-iPrbzim = 2-isopropyl-1-H-benzimidazole, are reported. Crystal structure studies revealed different coordination modes of the dipicolinate ligands; tridentate chelating for monomeric complex 1, and both tridentate chelating and bridging for similar polymeric complexes 2 and 3. Polymers 2 and 3 both contain two units, in which the Cu(II) central atoms Cu1 and Cu2 have different coordination polyhedra. The first unit {Cu(dipic)2} with Cu1 is connected to the second via two bidentate carboxylate groups of an μ3-bridging dipicolinate. In the second unit, Cu2 is coordinated by two imidazole nitrogen atoms from 2-ethyl-1-H-benzimidazole (2) or 2-isopropyl-1-H-benzimidazole (3) ligands. Complex 2 is of higher symmetry and has a localized Cu(II) atom Cu2 in a special position on the twofold axis. EPR spectra of all three Cu(II) complexes, which were measured at both room temperature and 98 K, indicate distorted tetragonal coordination spheres for all the Cu(II) atoms. The g-factor relation (g//> g > 2.0023) is consistent with a \(d_{{x^{2} - y^{2} }}\) ground electronic state in each case.


Datum: 24.04.2018


Syntheses, steric hindrance effects, luminescent properties and TD-DFT calculations for a series of copper(I) iodide coordination complexes

Abstract

A series of copper(I) coordination complexes, CuI(Phen)[2-(Dpp)bp] (1) (Phen = phenanthroline, 2-(Dpp)bp = 2-(Diphenylphosphino)-biphenyl), Cu2I2(Phen)[2-(Dpp)bp] (2), CuI(2-PBI)[2-(Dpp)bp] (3) and (2-PBI = 2-(pyridin-2-yl)-1H-benzo[d]imidazole) and CuI(Bipy)[2-(Dpp)bp] (Bipy = 2,2′-bipyridine) (4) have been synthesized. X-ray crystal structure studies revealed that complexes 1, 3 and 4 showed mononuclear structures with the copper atoms coordinated by iodide, a chelating nitrogen-donor ligand, and a monodentate phosphine ligand. However, the coordination centers display different distortions of their tetrahedral geometries, according to the steric hindrance of the bulky phosphine ligands. Complex 2 has a dinuclear structure, with trigonal and tetrahedral coordination centers. Variations in the aromatic system of the N-heterocyclic ligands result in different luminescence properties. Thus, the emission maxima for these complexes range from 580 to 642 nm, with lifetimes of τ = 0.6–0.9 and 1.6–4.2 μs. TD-DFT calculations reveal the origin of the luminescence to be metal–ligand charge transfer, as well as halogen–ligand charge transfer. The optical absorption spectra and thermal stabilities of the complexes have also been studied.


Datum: 20.04.2018


Three coordination polymers constructed from succinic acid and 1,4-bis(1H-imidazol-4-yl)benzene: synthesis, crystal structures, and properties

Abstract

Three coordination polymers involving transition metals, namely [Co(suc)(1,4-bib)(H2O)2]n (1), [Mn(suc)(1,4-bib)(H2O)2]n (2), [Cd(suc)(1,4-bib)]n (3) (H2suc = succinic acid, 1,4-bib = 1,4-bis(1H-imidazol-4-yl)benzene), have been synthesized under solvothermal conditions. All three compounds were characterized by single-crystal X-ray diffraction, elemental analysis, FTIR, UV–Vis spectroscopy, powder X-ray diffraction and thermogravimetric analyses. Compounds 1 and 2 show 2D metal–organic layers with the point symbol of {44·62}. The 3D framework of compound 3 displays a 4-connected dia net with the point symbol of {66} topology. Magnetic susceptibility studies of compound 1 indicate weak antiferromagnetic coupling between the Co(II) centers. The adsorption experiment results show that compound 3 exhibits rapid and selective separation of congo red over methylene blue and rhodamine B.


Datum: 18.04.2018


 


Category: Current Chemistry Research

Last update: 28.03.2018.






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