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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



Benzothiophene-based complexes mediated formation of cyclic carbonates by cycloaddition of carbon dioxide to epoxides under mild solvent-free conditions

Abstract

Transition metal complexes of the general formula [(S∩N∩N∩S)MCl2] (M: Cr(II), 2; Fe(II), 3, Co(II); 4; (S∩N∩N∩S): cis-1,2-N1,N2-bis{(benzo[b]thiophen-2-yl)methylene-diaminocyclohexane, S-DACH, 1) were prepared and characterized. The new complexes have been utilized as catalysts for the coupling reaction of carbon dioxide and the epoxides, styrene oxide (SO), and (±)-propylene oxide (PO), in the presence of bis(triphenylphosphoranylidene)imminium bromide (PPNBr) as a co-catalyst. The reactions were carried out under relatively low pressure and solvent-free conditions. The catalyst systems showed to be selective for the formation of cyclic carbonates. In general, the Cr(II)-based catalyst exhibited the highest activity for the coupling reaction of CO2 with both SO and (±)-PO compared with the corresponding iron(II) and cobalt(II) complexes under similar reaction conditions with turnover numbers values of 2445 and 1164 for the production of propylene carbonate and styrene carbonate, respectively.


Datum: 19.09.2019


Diiron butane-2,3-dithiolate complexes with monophosphine coligands: synthesis, characterization, and electrochemistry

Abstract

In this paper, three diiron butane-2,3-dithiolate complexes [Fe2(CO)5L{µ-SCH(CH3)CH(CH3)S}] [L = P(4-C6H4F)3, 2; P(4-C6H4OCH3)3, 3; P(3-C6H4Cl)3, 4] have been synthesized by CO substitution of the starting complex [Fe2(CO)6{µ-SCH(CH3)CH(CH3)S}] (1) with the corresponding monophosphine coligands in the presence of Me3NO·2H2O as the decarbonylating agent in 61‒74% yields. These complexes have been characterized by elemental analysis, IR, NMR spectroscopy, and single-crystal X-ray diffraction analysis. In addition, electrochemical studies revealed that these complexes can catalyze the reduction of proton to H2 in the presence of acetic acid under the electrochemical conditions.


Datum: 17.09.2019


A green approach to the preparation of triangular silver(I) 3,5-bis(trifluoromethyl)pyrazolate: crystal structures of two adducts with triethylammonium nitrate or benzoic acid

Abstract

An improved procedure is described herein for the synthesis of triangular Ag(I) 3,5-bis(trifluoromethyl)pyrazolate ({[3,5-(CF3)2Pz]Ag}3), which involves initial preparation of its adducts with triethylammonium nitrate or benzoic acid, namely {[3,5-(CF3)2Pz]Ag}3·(Et3NH·NO3)2 (1) and {[3,5-(CF3)2Pz]Ag}3·(PhCOOH)2 (2), followed by removal of the nitrate and benzoic acid by washing or extraction with water to afford the pristine trisilver complex {[3,5-(CF3)2Pz]Ag}3. X-ray diffraction analysis on 1 and 2 reveals that {[3,5-(CF3)2Pz]Ag}3, acting as a π-acidic host, can combine with guest molecules/ions (NO3, PhCOOH) by weak Ag–O/C coordination bonds, π–π stacking and C–H···F interactions. Our proposed synthetic procedure for {[3,5-(CF3)2Pz]Ag}3 can be easily carried out at room temperature, without using complex Schlenk techniques or hazardous organic solvents such as benzene and toluene, thus representing a green and facile approach to this well-recognized π-acidic complex.


Datum: 16.09.2019


Synthesis, characterization, photophysical, and redox properties of three trinuclear Ru(II) polypyridyl complexes possessing 5-amino-1,10-phenanthroline ligands

Abstract

Three ruthenium(II) polypyridyl complexes with 5-amino-1,10-phenanthroline ligands have been successfully designed and synthesized. They have been fully characterized by ESI-MS, ESI-HRMS, 1H NMR, and elemental analyses. The photophysical and electrochemical properties of the three complexes have been investigated in organic solvent. The geometrical configuration and the electron density distribution in the frontier molecular orbitals of the three complexes have been studied. The three complexes show metal-to-ligand charge transfer (1MLCT) absorption at 445 nm, and intense triplet metal-to-ligand (3MLCT) emission at around 619 nm in fluid solution at 298 K and 580 nm in low-temperature glass. Electrochemical studies of the three complexes are consistent with one RuIII/II reversible couple at around 1.31 V accompanied by three ligand-centered reduction couples.


Datum: 01.09.2019


Synthesis, characterization and anti-tumor activity of Pd(II) complexes with 4,5-benzo-3H-1,2-dithiole-3-thione

Abstract

Reaction of Na2[PdCl4] with two equivalents of 4,5-benzo-3H-1,2-dithiole-3-thione (btt) affords cis-[PdCl21-btt)2] (1), which provides a convenient entry into mixed-ligand btt complexes. Addition of one equivalent of a range of diamines or diphosphines gives the salts [Pd(κ1-btt)22-diamine)]Cl2 (2ad) (diamine = en, dap, bipy, phen) and [Pd(btt)22-diphosphine)]Cl2 (3ac) (diphosphine = dppe, dppp, dppf) in good yields. In contrast, two equivalents of dppm result in [Pd(κ1-btt)21-dppm)2]Cl2 (4), where the diphosphine binds in a monodentate fashion. Two equivalents of PPh3 result in a mixture of cis- and trans-isomers of [Pd(κ1-btt)2(PPh3)2]Cl2 (5ab) (ca. 1:5 ratio); the pure trans-isomer 5b was isolated by ion-exchange chromatography. The cis-isomer 5a could be synthesized independently from the reaction of cis-[PdCl2(PPh3)2] with two equivalents of btt. In all of these complexes, the btt ligand binds in a monodentate manner through the exocyclic thione sulfur. The anti-tumor activities of representative examples, cis-[PdCl21-btt)2] (1), cis-[Pd(κ1-btt)21-dppm)2]Cl2 (4) and cis-[Pd(κ1-btt)2(PPh3)2] (5a), were evaluated by cell proliferation assays and phase-contrast microscopy against prostate cancer cell lines PC3, DU145 and LNCaP, with complexes 1 and 4 showing potent anti-proliferative effects (TGI values of 19.2 and 21.1 µg/mL, respectively) against LnCaP cells.

Graphical abstract


Datum: 01.09.2019


A theoretical study of Fe(PMe 3 ) 4 -catalyzed anti-Markovnikov addition of aromatics to alkenes to provide linear alkylation products

Abstract

The mechanisms and regioselectivities of Fe(0)-catalyzed alkylation of aromatic compounds with alkenes were explored by DFT calculations. Our calculations show that these systems tend to undergo anti-Markovnikov addition. The influence of steric effects on the reaction mechanism has been investigated. The results indicate that the reaction is more likely to provide the linear product with dissociation of the 1PMe3 ligand. The reductive elimination is the rate-determining step of the whole process, such that the electrostatic interactions of the reaction site and the steric hindrance of the trimethylsilyl groups are favorable for the anti-Markovnikov rather than the Markovnikov addition pathway. Our calculations provide insights into the regioselective origin of the alkylation of aromatic compounds mediated by Fe(PMe3)4.


Datum: 01.09.2019


Double-shell structural polyaniline-derived TiO 2 hollow spheres for enhanced photocatalytic activity

Abstract

Polyaniline (PANI) is a conducting polymer which has been employed as a photosensitizer for enhancing the performance of a number of photocatalysts. Herein, we describe the synthesis of organic–inorganic hybrid materials in order to enhance the photocatalytic activity of double-shell TiO2/PANI hollow spheres (TAHSs), which were fabricated by means of sol–gel and in situ polymerization processes. The physicochemical properties of the PANI-modified TiO2 hollow spheres were investigated by a variety of techniques. The effect of the PANI shell layer on the photocatalytic activity of TAHSs was elucidated. With the optimal PANI content, the resultant TiO2/PANI hybrid materials exhibited remarkably enhanced UV and visible light photocatalytic degradation of aqueous methyl orange, far exceeding the activity of bare TiO2 hollow spheres. The synergistic effect between TiO2 and PANI is explained in terms of the improved separation of photogenerated electron–hole pairs.


Datum: 01.09.2019


Mizoroki–Heck cross-coupling reactions using palladium immobilized on DABCO-functionalized silica

Abstract

A heterogeneous palladium catalyst supported on silica modified by DABCO has been prepared by post-synthetic modification of silica gel. This heterogeneous catalytic system exhibits high activity and stability in the Mizoroki–Heck cross-coupling reaction of various aryl halides with olefins. The reaction proceeds efficiently under efficiently under mild mild reaction conditions and high yield, with the formation of E-isomers selectively. Moreover, we successfully established a gram-scale synthesis, and the catalyst was reused for up to ten catalytic cycles.


Datum: 01.09.2019


Synthesis and X-ray crystal structures of some isothiosemicarbazone complexes

Abstract

Four complexes of a new isothiosemicarbazone ligand have been prepared and characterized as μ2-pip-(NiL)2 (1), MnL2 (2), UO2L(BrSal)BuOH (3) and (μ2-MoO2L)2 (4) (H2L = 2-hydroxyacetophenone S-allyl isothiosemicarbazone.hydrobromide, BrSal = 5-bromosalicylaldehyde, pip = piperazine). All four complexes were characterized by X-ray crystallography, IR and elemental analyses. Complex 1 has a square planar coordination geometry in a binuclear arrangement such that both Ni atoms are coordinated to the phenolic-O, azomethine-N and thioamide-N atoms of L, and the bridging piperazine occupies the fourth position. For complex 2, the Mn atom connects to two N2O tridentate ligands in a distorted octahedron. The pentagonal bipyramidal geometry of complex 3 is provided by the tetradentate N2O2 ligand, n-butanol, and two oxo ligands around the uranium center. Finally, in the binuclear Mo complex (4), two N2O ligands coordinate to each molybdenyl center, together with the phenoxide-O donor of the adjacent molecule.


Datum: 01.09.2019


Studies of the anticancer activities of ruthenium(II) polypyridyl complexes toward human hepatocellular carcinoma BEL-7402 cells

Abstract

Two ruthenium(II) polypyridyl complexes formulated as [Ru(bpy)2(THPDP)](PF6)2 (1) and [Ru(ttbpy)2(THPDP)](PF6)2 (ttbpy = 4,4ʹ-ditertiary butyl-2,2ʹ-bipyridine) (2) were synthesized and characterized by elemental analysis, 1H NMR, 13C NMR and UV–Vis spectra. The cytotoxic activities of the complexes against cancer cell lines BEL-7402, A549, SGC-7901, HeLa and normal NIH3T3 cells were investigated by 3-(4,5-dimethylthiazole)-2,5-diphenyltetrazolium bromide (MTT) methods. The complexes show moderate cytotoxicity toward BEL-7402 and HeLa cells. The changes in mitochondrial membrane potential, intracellular Ca2+ and reactive oxygen species were studied by fluorescence microscopy. Both complexes can increase intracellular Ca2+ concentrations and ROS levels and induce a decrease in mitochondrial membrane potential. They also inhibit cell invasion and suppress cell proliferation at the G0/G1 phase. Additionally, they activate caspase 3, cleave PARP and regulate the expression of Bcl-2 family proteins. In short, the complexes induce apoptosis in BEL-7402 cells through a ROS-mediated mitochondria dysfunction pathway.


Datum: 01.09.2019


Ruthenium(II)-NHC-catalyzed (NHC = perhydrobenzimidazol-2-ylidene) alkylation of amines using the hydrogen borrowing methodology under solvent-free conditions

Abstract

New ruthenium(II) complexes with N-heterocyclic carbene ligand were synthesized by transmetalation reactions between silver(I) N-heterocyclic carbene complexes and [RuCl2(p-cymene)]2. The complexes were characterized by physicochemical and spectroscopic methods. These ruthenium complexes were applied to the N-monoalkylation of aromatic amines with a wide range of primary alcohols under solvent-free conditions using the hydrogen borrowing strategy. The catalytic reactions using all ruthenium complexes resulted in N-monoalkylated products with high selectivities using furfuryl alcohol as the alkylating agent.


Datum: 01.09.2019


Synthesis and crystal structures of manganese(III) complexes derived from bis-Schiff bases with antibacterial activity

Abstract

Two mononuclear Mn(III) complexes, [MnL1(N3)(OH2)] (1) and [MnL2L′] (2), where L1 and L2 are the dianionic forms of N,N′-bis(3-ethoxysalicylidene)-1,2-ethanediamine (H2L1) and N,N′-bis(3,5-dichlorosalicylidene)-1,4-butanediamine (H2L2), respectively, and L′ is the deprotonated form of 2,4-dichloro-6-(dimethoxymethyl)phenol (HL′), have been synthesized and characterized. The complexes were characterized by physico-chemical and spectroscopic methods. The Mn atoms in the structures are in octahedral coordination. In the crystal structure of complex (1), molecules are linked through intermolecular O–H···O hydrogen bonds to form dimers. In both complexes, there exist π···π interactions among molecules. The complexes and the Schiff bases were assayed for antibacterial activities by MTT method.


Datum: 01.09.2019


Reductions of the cisplatin-based platinum(IV) prodrug cis,cis,trans -[Pt(NH 3 ) 2 Cl 2 Br 2 ] by predominant biological thiols: kinetic and mechanistic studies

Abstract

The reductions of the anticancer-active platinum(IV) complex cis,cis,trans-[Pt(NH3)2Cl2Br2] by three predominant biological thiols (cysteine, homocysteine and glutathione) were studied kinetically in the present work. The reductions show second-order kinetics, being first order each in [Pt(IV)] and in [thiol]. The second-order rate constant k′ was increased dramatically when the pH of reaction media was increased. Thiols were oxidized to their intermolecular disulfides. Accordingly, mechanisms containing a transition state S-Br-Pt are proposed, from which the overall rate laws were deduced. The rate-determining rate constants were also calculated by simulation of k′-pH data. The reactivity trend for the reduction of cis,cis,trans-[Pt(NH3)2Cl2Br2] is ordered as Cys > GSH > Hcy by comparison of k′ under the same reaction conditions. The rate for the reduction of the axial bromide-coordinated Pt(IV) complex is much faster than that of reduction of the axial chloride-coordinated one. In addition, the reduction rate is related to the equatorial and axial ligands.


Datum: 01.09.2019


An efficient synthetic approach towards a single diastereomer of (2 R ,3 R )- N 2 , N 3 -bis(( S )-1-phenylethyl)butane-2,3-diamine via metalation and demetalation

Abstract

A facile synthetic approach has been adopted towards the synthesis of (2R,3R)-N2,N3-bis((S)-1-phenylethyl)butane-2,3-diamine via demetalation of its dichloro Zn(II) complex, which itself was separated from a mixture of diastereomeric Zn(II) complexes by fractional crystallization. The synthesized chiral 1,2-diamine ligand was evaluated as a chiral auxiliary for the Cu(II)-catalysed asymmetric Henry reaction of 3-phenylpropanal and nitromethane, yielding (S)-1-nitro-4-phenylbutan-2-ol in excellent yields (up to 99%) and enantioselectivities (up to 97%).

Graphic abstract

A facile synthetic approach towards (2R,3R)-N2,N3-bis((S)-1-phenylethyl)butane-2,3-diamine (2b) via fractional crystallization and demetalation of its Zn(II) complex has been adopted. 2b served as a highly enantioselective pro-ligand with Cu(OAc)2 for asymmetric Henry reaction of 3-phenylpropanal and nitromethane in the presence of base with 97% > ee and 99% yield.


Datum: 30.08.2019


Polyethyleneimine-oleic acid micelle-stabilized gold nanoparticles for reduction of 4-nitrophenol with enhanced performance

Abstract

Noble metal nanoparticles have been drawing great attention for the treatment of water pollutants. The catalytic activity of noble metal nanoparticles is usually reduced due to their aggregation. Amphiphilic molecule micelles have potential to stabilize the noble nanoparticles against aggregation. In this study, a novel facile method was reported for preparing polyethyleneimine-oleic acid (PEI-oleic acid) micelle-stabilized gold nanoparticles (PO-AuNPsn), where the gold nanoparticles (AuNPs) were embedded in the shell area of micelles. When the molar ratio of [N] to [Au] was 50, 100, and 200, the mean diameter of AuNPs was 3.52 ± 0.42, 3.11 ± 0.28, and 2.85 ± 0.48 nm, respectively. The corresponding zeta potential of the PO-AuNPsn was determined to be 26.2, 28.9 and 35.7 mV, respectively. Furthermore, PO-AuNPsn remained stable in aqueous solution at room temperature for more than 1 month. More importantly, PO-AuNPsn had higher catalytic activity for 4-nitrophenol (4-NP) reduction in aqueous solution compared with previous reports, where PO-AuNPs200 showed a Knor value of 9367 s−1 g−1. It is believed that PO-AuNPsn showed high catalytic activity because of their small size, high stability, and the location of AuNPs in the shell area, which made it easier for AuNPs to contact with 4-NP. The method described in this report represents a new method to prepare small and stable noble metal nanoparticles for catalytic applications in the future.


Datum: 28.08.2019


Two silver(I) complexes based on dicarboxylate and flexible bis(benzimidazole) ligands: synthesis, crystal structures, sensing and photocatalytic properties

Abstract

Two Ag(I) complexes, namely [Ag2(L1)2(HMIP)2·H2O]n (1) and [Ag2(L2)2(HPA)2]n (2) (L1 = 1,6-bis(2-methylbenzimidazol-1-yl)hexane, L2 = 1,6-bis(benzimidazol-1-yl)hexane, H2MIP = 5-methylisophthalic acid, H2PA = phthalic acid), were hydrothermally synthesized and characterized by physicochemical and spectroscopic methods. 1 Processes a binuclear Ag(I) structure which is further extended into a 2D supramolecular network by hydrogen bonds and ππ stacking interactions. 2 Features a 1D meandering chain which is linked into a 3D supramolecular network by Ag···O and ππ stacking interactions. Complex 1  is shown to be a highly sensitive material for luminescence detecting Fe3+ in aqueous solution. These complexes display high photocatalytic activities for degradation of methylene blue under UV irradiation.


Datum: 26.08.2019


N ′ N ′ N pincer and N ′ N bidentate(pyrazolylpyridyl) Rh(I) complexes as catalyst precursors for hydroformylation of olefins

Abstract

The industrial process of hydroformylation or the oxo process has been used for many years in the production of aldehydes from alkenes. Different metals have been used as efficient catalysts for hydroformylation, in which linear and branched aldehydes are the products obtained; therefore, the development of new catalysts for hydroformylation with high selectivity to aldehydes is important. Rhodium complexes 69 were synthesized using [RhCl(CO)2]2, or [RhCl(COD)]2, with either pyrazolylpyridyl NNN pincer ligands or a pyrazolylpyridyl NN ligand. These complexes were then evaluated as catalyst precursors in the hydroformylation reaction using a variety of alkenes. The catalysts all showed activity in hydroformylation but the most active catalyst was methyl-substituted pyrazolyl–rhodium complex 7 following optimization of temperature, syngas pressure and amount of catalyst. Other olefinic substrates were used for hydroformylation in the presence of 7 under the optimum hydroformylation conditions. Undecene and dodecene as substrates only showed minimal formation of aldehydes with predominantly isomerization of the alkene being observed.


Datum: 24.08.2019


Simultaneous efficient adsorption and photocatalytic degradation of methylene blue over iron(III)-based metal–organic frameworks: a comparative study

Abstract

Here, we prepared a series of Fe-based metal organic frameworks (MOFs), including MIL-53(Fe), NH2-MIL-53(Fe), MIL-88B(Fe) and NH2-MIL-88B(Fe), via an oil bath process and used them to remove methylene blue under visible light. A comparative study of NH2-MILs and Fe-MILs was conducted. The experimental results showed that the presence of amino groups could improve the adsorption capacities of NH2-MILs, which was attributed to hydrogen bonding interactions and ππ stacking between the amino groups of the dye molecules and the amino-functionalized MOFs. The photocatalytic activities of NH2-MILs under visible light were higher than those of Fe-MILs, owing to the enhancement of visible-light absorption, the decrease in the band gap and the improvement of the adsorption capacity. After several photodegradation experiments, the catalytic activities decreased and could be restored by irradiating the catalysts with ultraviolet light. This study indicated that the amino-functionalized materials had great potential for wastewater treatment and resource utilization.

Graphic abstract


Datum: 21.08.2019


Synthesis and structural characterization of (η 5 -Dp)Ru(PPh 3 ) 2 H (Dp = C 8 H 9 − , 1,2-dihydropentalenyl)

Abstract

5-Dp)Ru(PPh3)2H (Dp = C8H9, 1,2-dihydropentalenyl) was synthesized in 90% yield by reaction of (η5-Dp)Ru(PPh3)2Cl with sodium formate. (η5-Dp)Ru(PPh3)2H was characterized by 1H and 31P NMR spectroscopy and IR spectroscopy. The Ru–H appears in the 1H NMR spectrum upfield at −11.6 ppm, indicative of a metal hydride. In the IR spectrum, the νRu–H was observed at 1920 cm−1. The solid-state structure of (η5-Dp)Ru(PPh3)2H (1) was determined by X-ray crystallography. Compound 1 has similar structural parameters to (η5-Cp)Ru(PPh3)2H and (η5-Ind)Ru(PPh3)2H.


Datum: 13.08.2019


Kinetic and mechanistic analysis of oxidation of 2-furoic hydrazide by hexachloroirradate(IV) in a wide pH range

Abstract

Oxidation of 2-furoic hydrazide (FH) by hexachloroiridate(IV) ([IrCl6]2−) was studied kinetically in a wide pH range in aqueous solution of 1.0 M ionic strength. The oxidation reaction followed well-defined second-order kinetics: − d[IrCl62−]/dt = k′[FH]tot[IrCl62−], where [FH]tot denotes the total concentration of FH and k′ stands for the observed second-order rate constants. The established k′–pH profile displays that k′ increases drastically with pH and a plateau region exists between pH 4 and 6. A stoichiometric ratio of Δ[FH]tot/Δ[IrCl62−] = 1/4 was revealed by spectrophotometric titrations. 1H NMR spectroscopic studies indicated that FH was cleanly oxidized to 2-furoic acid. The kinetic data suggest a reaction mechanism in which all the three protolysis species of FH react with [IrCl6]2− in parallel, forming the rate-determining steps. Two stabilized hydrazyl radicals are generated in the rate-determining steps, in which a single electron is transferred to [IrCl6]2−. The two hydrazyl radicals react rapidly in consecutive steps requiring 3 mol of Ir(IV) to form 2-furoic acid as the final product. Rate constants of the rate-determining steps were deduced through a simulation of the rate expression to the k′–pH dependency data. Values of these rate constants demonstrate that the three protolysis species of FH have a huge reactivity span, changing by about 109 times toward reduction in [IrCl6]2− and that FH can be readily oxidized in neutral and basic media. Rapid scan spectra and the measured activation parameters suggest that an outer-sphere electron transfer is probably taking place in each of the rate-determining steps. This is the first kinetic study on the oxidation reactions of FH and provides concurrently the protolysis constants of FH (pKa1 = 3.04 ± 0.08 and pKa2 = 11.6 ± 0.1) at 25.0 °C and 1.0 M ionic strength.


Datum: 10.08.2019


 


Category: Current Chemistry Research

Last update: 28.03.2018.






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