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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



Photoinduced reactivity and cytotoxicity of a series of zinc(II)–flavonolate derivative complexes

Abstract

A series of Zn(II)-based complexes as photoinduced carbon-monoxide-releasing molecules (photoCORMs), viz. (L)Zn(R)]ClO4 with L = tris(pyridine-2-ylmethyl)amine (TPA), N,N-((5-estermethyl-2-pyridyl)methyl)-bis(2-pyridylmethyl) amine (5-COOCH3TPA), N,N-(bis(5-estermethyl-2-pyridyl)methyl)-(2-pyridylmethyl) amine [(5-COOCH3)2TPA], or N,N-((6-estermethyl-2-pyridyl)methyl)-bis(2-pyridylmethyl) amine (6-COOCH3TPA) and R = 4-dimethylaminoflavonol [4-N(Me)2FLH], 4-diethylaminoflavonol [4-N(Et)2FLH], or 4-methoxyflavonol (4-MeOFLH), have been prepared and characterized. When dissolved in CH3CN or 1:1 H2O:dimethylsulfoxide (DMSO) in presence of O2, visible light (λmax ranging from 417 to 462 nm) induced dioxygenase-type reactions to release CO quantitatively from these complexes. Moreover, the intracellular uptake and CO releasing reactivity were confirmed by the change of their fluorescent properties observed under fluorescence microscopy. The cytotoxicity of the complexes demonstrates that they exhibit good biocompatibility in the concentration range from 1 to 50 μM. The solid complexes are stable in air for more than 60 days, and their aqueous solutions are also stable for 96 h under anaerobic or dark condition. The remarkable stability and biocompatibility of the complexes are indispensable properties for use in pharmaceutical chemistry.

Graphic abstract


Datum: 16.03.2020


A kinetic investigation of mononuclear trans-platinum(II) complexes with mixed amine ligands

Abstract

This study was aimed at investigating the substitution behaviour of mononuclear trans-platinum(II) complexes with mixed amine ligands. The rate of substitution of the chloride moieties from the complexes trans-Pt(NH3)(NH2C2H5)Cl2 (tPt2), trans-Pt(NH3)(NH2C3H7)Cl2 (tPt3), trans-Pt(NH3)(NH2C4H9)Cl2 (tPt4) and trans-Pt(NH3)(NH2C5H11)Cl2 (tPt5), by three nucleophiles, viz. thiourea (TU), 1-methyl-2-thiourea (MTU) and 1,3-dimethyl-2-thiourea (DMTU), was studied by stopped-flow spectrophotometry using a large excess of nucleophile. Pseudo-first-order rate constants (kobs) were measured as a function of nucleophile concentration and temperature. Reactions were first order in both [complex] and [nucleophile] and therefore second-order overall (rate = kobs[complex] where kobs = k2[nucleophile]). The kinetics are consistent with a stepwise mechanism involving rate determining substitution of the first chloride followed by a fast second substitution step, with no intermediates being detected. The reactivity of the complexes was largely dependent on the length of the alkyl chain of the alkylamine moiety of the complexes. Computational modelling using density functional theory calculations showed that an increase in chain length by a methylene unit has no direct electronic consequence on the metal centre but did, however, pose significant steric hindrance on the substitution sites due to the flexibility of the alkyl chains and thus governed the overall reaction pattern. 195Pt NMR kinetic studies established that the mixed amine ligands remain coordinated to the metal centre in the final kinetic product. This implies that mononuclear trans-platinum(II) complexes are resistant to complete substitution of ligands by the incoming thiourea nucleophiles at the reaction sites. The reactions follow an associative mechanism of substitution.


Datum: 12.03.2020


The rate of substitution from η 6 -arene ruthenium(II) complexes

Abstract

The rate and mechanism of substitution in the Ru(II) complexes (C1–C6) by thiourea nucleophiles was studied at pH 2 and rate constants measured as a function of nucleophile concentrations and temperature using spectrometric methods. There is increased electron density at the Ru metal atom of C2 as a result of inductive donation by substituents on the arene ligand, making it less positive and therefore less reactive than C1. For the complexes C3–C6 bearing the 2,2′-bipyridyl ligand, the aqua ligands are located trans to the arene ligands, and hence, their reactivity increases in accordance to the number and type of alkyl substituents on the η6-arene ligands which donate inductively into the π-molecular orbitals, causing increased trans labialisation of the coordinated aquo co-ligand. Compared to the reactivity of triaquo complex (C1), the auxiliary bipyridyl ligand of (C3) complex lowers the rate of substitution for the later complex by a factor of about 100, possibly due to its steric hindrance at the Ru(II) metal centre. The significantly negative activation entropies and positive activation enthalpies suggest an associative mode of substitution. The reactivity of the nucleophiles follow the order DMTU > TU > TMTU.


Datum: 03.03.2020


Three supramolecular trinuclear nickel(II) complexes based on Salamo-type chelating ligand: syntheses, crystal structures, solvent effect, Hirshfeld surface analysis and DFT calculation

Abstract

Three Ni(II) complexes {[NiL(μ-OAc)(CH3CH2OH)]2Ni} (1), {[NiL(μ-OAc)(CH3OH)]2Ni]·2CH2Cl2·2CH3OH (2) and {[NiL(μ-OAc)(CH3OH)]2Ni}·1.5CH3OH (3) based on a Salamo-type bis-oxime ligand (H2L = 2,2′-[ethylenedioxybis(nitrilo-methylidyne)]dinaphthol) have been synthesized and characterized by physicochemical and spectroscopic methods. The complexes 1, 2 and 3 are all trinuclear structures, and the center Ni(II) ions are six-coordinated and show the slightly distorted octahedral coordination. They all consist of three Ni(II) ions, two deprotonated L2- units, two μ-acetato ligands and two coordinated solvent molecules, as well as the crystallizing solvent molecules. Although the molecular structures of the Ni(II) complexes 1, 2 and 3 are similar to each other, obtained in different solvents, the supramolecular structures are entirely different. The complexes 1, 2 and 3 possess the self-assembled infinite 1D, 3D and 2D supramolecular structures via different intermolecular interactions (hydrogen bonds, C–H···π and π···π stacking interaction), respectively. But complex 2 formed a 3D structures by intramolecular hydrogen bonds. It is significant that the solvent molecules have obvious effects on the optical properties and molecular configuration. The Hirshfeld surface analysis showed that the short-range forces of the hydrogen bonds in complexes 1, 2 and 3 accounted for 67.8%, 44.6% and 52.7%, respectively. The molecular orbital energies for ligand H2L and complex 1 were obtained by DFT calculation, and the electron distribution, energy level and energy gap of HOMO and LUMO were given.


Datum: 13.02.2020


Water-mediated proton conduction in two stable fluorophenyl imidazole dicarboxylate-based cadmium(II) complexes

Abstract

Recently, crystalline solid materials as proton conductors have attracted intensive attention. Herein, two highly stable complexes, 2D coordination polymer [Cd(3,5-DFPhH2IDC)2]·H2O (1) and supramolecule [Cd(3,5-DFPhH2IDC)2(phen)(H2O)]·0.5H2O (2) (phen = 1,10-phenanthroline), have been synthesized by using 2-(3,5-difluorophenyl)imidazole-4,5-dicarboxylic acid (3,5-DFPhH3IDC) as organic ligand. The water-assisted proton-conductive properties of 1 and 2 were investigated by impedance spectroscopy. Notably, the proton conductivity of both complexes attains the optimized value of 4.90 × 10−5 S cm−1 for 1 and 2.04 × 10−4 S cm−1 for 2 under 100 °C and 98% RH. Consequently, their proton-conducting mechanisms based on the Ea values were highlighted.

Graphic abstract


Datum: 06.02.2020


Modification of porous lignin with metalloporphyrin as an efficient catalyst for the synthesis of cyclic carbonates

Abstract

The conversion of carbon dioxide into useful chemical raw materials is a necessary development for advancing carbon dioxide capture and storage technology. In this work, a Friedel–Crafts reaction of lignin and metalloporphyrin was used to produce a lignin-based porous organic polymer (P-(L-FeTPP)) with a surface area of up to 1153 m2 g−1. P-(L-FeTPP)) efficiently catalyzed the cycloaddition reactions of epoxides and CO2 under solvent-free conditions, with porphyrin iron acting as an active center. The product yield reached up to 99.6% after 12 h under 1 MPa CO2 and 70 °C. A turnover number of 1481 was achieved, indicating that this catalyst is much more active than its homogeneous counterpart and is one of the most efficient lignin-supported heterogeneous catalysts ever reported. This method for the in situ incorporation of a metalloporphyrin into a lignin skeleton greatly improved the stability of the metal catalyst, and P-(L-FeTPP) was readily recycled and reused more than six times without any significant loss of catalytic activity. Thus, this catalyst design is promising for practical applications, including the industrial production of cyclic carbonates.


Datum: 01.02.2020


Pseudohalide-directed assemblies of Cu(II) coordination polymers with diverse structures and dye adsorption behaviors

Abstract

Assembly of 3,4-bis(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole (L334) and CuBr2 without or with the presence of thiocyanate (SCN)/dicyanamide [dca, N(CN)2] anion produces three Cu(II) coordination polymers, {[Cu(L334)(H2O)2](Br)2(CH3OH)}n (1), {[Cu(L334)(SCN)2(H2O)](H2O)(EA)}n (2) (EA = ethyl acetate), and [Cu(L334)(dca)2]n (3). The crystal structures for 1 and 3 show different 2D layered coordination networks, whereas that for 2 represents a distinct 1D coordination pattern. The above results demonstrate that the addition of pseudohalide anions plays an important role in structural construction of coordination architectures. Moreover, 1 exhibits the best adsorption capacity toward methyl orange (MO) dye.


Datum: 01.02.2020


Insight into molecular packing effects on transesterification catalysis of zinc(II) coordination polymers

Abstract

Self-assembly of ZnX2 (X = ClO4 and CF3SO3) with naphthalene-2,6-diyl-diisonicotinate (L) gives rise to the 2D sheet structures with composition of [ZnL2(H2O)2](ClO4)2·H2O and [ZnL2(CF3SO3)2], respectively. [ZnL2(H2O)2](ClO4)2·H2O is packed in an interpenetration mode, whereas [ZnL2(CF3SO3)2] exists as a simple 2D network in the crystalline solid state. These two crystals have been employed as hetero-catalysts for transesterification reactions of phenylacetate with alcohol. The catalytic effect on the transesterification reaction shows the order of [ZnL2(H2O)2](ClO4)2·H2O > Zn(CF3SO3)2 > [ZnL2(OTf)2] > Zn(ClO4)2, which indicate that molecular packing is an important factor in the catalysis.


Datum: 01.02.2020


A novel coordination polymer based on 2,6-naphthalenedicarboxylic acid: synthesis, crystal structure and luminescence sensing

Abstract

A novel Cd(II)-based coordination polymer, namely {[Cd3L3(dbp)2]}n (1), was solvothermally prepared based on the rigid ligand 2,6-naphthalenedicarboxylic acid (H2L) and N-donor linker 4,4′-dimethyl-2,2′-bipyridine (dbp). The single-crystal X-ray diffraction analysis shows that compound 1 possesses a fascinating 3D architecture, constructed from a trinuclear secondary building unit [Cd3(COOR)6] and linear L2− linker. The whole structure of compound 1 can be simplified as uninodal 6-connected sxb network with Schlafli symbol of {485,463}. Compound 1 exhibits strong photoluminescent emissions with emission peak at 425 nm. Most strikingly, 1 could be selectively quenched by Cu2+ ion and nitrobenzene (NB) as potential luminescent sensory material. Meanwhile, vapor-phase fluorescence response of 1 toward NB was also investigated.


Datum: 01.02.2020


Ruthenium [NNN] and [NCN]-type pincer complexes with phosphine coligands: synthesis, structures and catalytic applications

Abstract

A series of ruthenium [NNN]- or [NCN]-type complexes (37) bearing PPh3 ancillary ligands have been synthesized from pyridine- or phenylene-bridged bis(triazoles) 1 and 2. In the case of [NNN]-pincer complex 3, an unusual and unexpected cis-orientation adopted by two sterically demanding PPh3 ligands was observed, and such configuration proved to be unchanged in solution for a long time. By contrast and as expected, the two phosphines are found to be trans to each other in the case of [NCN]-type pincer complex 4, but an oxidation of RuII center to RuIII occurred. Complex cis-3 underwent ligand exchanges leading to the formations of diphosphine derivatives 5 and 6. As a representative, cis-3 was treated with the base in isopropanol affording a mixture of Ru–hydrido complexes with various phosphine binding modes, one of which (trans-7) bearing two trans-standing phosphines has been successfully isolated and fully characterized. The catalytic performances of all newly synthesized Ru complexes have been examined and compared in transfer hydrogenations of ketones and enones, in which mono-phosphine complexes proved to be significantly superior to their diphosphine counterparts. The catalytic process proved to involve Ru–H key intermediates, but the trans-oriented Ru–H species is unlikely to be the main catalytic contributor. In particular, the best performer cis-3 exhibits high chemoselectivity in certain cases catalyzing α,β-unsaturated ketones, whose behavior is quite different compared to most precedents.


Datum: 01.02.2020


Syntheses and crystal structures of ruthenium carbonyl complexes containing pyridine-alkoxide ligands

Abstract

The reactions of pyridine alcohols PyCH2C(R1R2)OH [R1 = H, R2 = 4-BrC6H4 (1); R1 = H, R2 = 4-CF3C6H4 (2); R1 = CH3; R2 = Ph (3)] with Ru3(CO)12 in refluxing toluene gave three mononuclear ruthenium carbonyl complexes [PyCH = C(4-BrC6H4)O]2Ru(CO)2 (4), [PyCH = C(4-CF3C6H4)O][PyCH = C(4-CF3C6H4)]Ru(CO)2 (5), [PyCH = C(4-CF3C6H4)O]2Ru(CO)2 (6) and one dinuclear ruthenium carbonyl complexes [PyCH2C(CH3)(Ph)O]2Ru2(CO)4 (7). Four new complexes 47 were characterized by elemental analysis, IR, 1H NMR and 13C NMR spectroscopy. The molecular structures of these complexes were determined by X-ray crystal diffraction analysis.


Datum: 01.02.2020


Ruthenium(II) complexes containing a pendant methanol amidogen induce apoptosis in SGC-7901 cells through a ROS-mediated mitochondrial dysfunction pathway

Abstract

A phenanthrene derivative with a pendant methanol amidogen TFCPIP and its two ruthenium(II) complexes [Ru(phen)2(TFCPIP)](ClO4)2 (1) and [Ru(dmp)2(TFCPIP)](ClO4)2 (2) (phen = 1,10-phenanthroline, dmp = 2,9-dimethyl-1,10-phenanthroline, TFCPIP = 2-(2,3,5,6-tetrafluoro-4-aminoethanolphenyl)[4,5-f]-imidazo[1,10]phenanthroline) were synthesized, and the anticancer properties of the two complexes were examined. Both the complexes displayed certain anticancer activities against the selected SGC-7901, BEL-7402, HeLa, A549, MG-63, HepG2, PC-12 and SiHa cancer cells, with the highest cytotoxic activities against SGC-7901. The cell biology experiments for exploring toxicity mechanism with fluorescence imaging technique and flow cytometry demonstrated that the complexes can trigger apoptosis of SGC-7901 cells with an increase in ROS level, a decrease in mitochondrial membrane potential, and effectively inhibit cell invasion and cell growth at G2/M phase, implicating that the complexes induce cellular apoptosis through a ROS-mediated mitochondrial dysfunction pathway.


Datum: 01.02.2020


Aerobic oxidation of alcohol by model complexes relevant to metal site galactose oxidase: role of copper(I) intermediate, evidence for the generation of end-on copper(II)–OOH species and catalytic promiscuity for oxidation of benzyl alcohol, catechol and o -aminophenol

Abstract

Tridentate ligands having meridional NNO donor centres were designed and synthesized mimicking the copper coordination in the metal site of galactose oxidase enzyme. Mononuclear copper complexes [Cu(L1)Cl] (1) (L1H = (E)-2-((2-phenyl-2-(pyridin-2-yl)hydrazono)methyl)phenol), [Cu(L2)Cl] (2) (L2H = (E)-4-methyl-2-((2-phenyl-2-(pyridin-2-yl)hydrazono)methyl)phenol), [Cu(L3)Cl] (3) (L3H = (E)-1-((2-phenyl-2-(pyridin-2-yl)hydrazono)methyl)naphthalen-2-ol), [Cu(L4)Cl] (4) (L4H = (E)-2-((2-phenyl-2-(pyridin-2-yl)hydrazono)methyl)phenol), [Cu(L5)Cl] (5) (L5H = (E)-2-((2-phenyl-2-(pyridin-2-yl)hydrazono)methyl)phenol), and [Cu(L6)Cl] (6) (L6H = (E)-2,4-di-tert-butyl-6-(((pyridin-2-ylmethyl)imino)methyl)phenol) were synthesized and characterized. Molecular structure of complex 3 was determined by single crystal X-ray crystallography. Phenoxyl radical complexes were generated in solution via chemical oxidation using ceric ammonium nitrate (CAN), and the radical complexes were characterized by UV–Vis–NIR spectrophotometer. DFT calculations were performed at B3LYP level to optimize the ground-state molecular geometry of the complexes. To understand the electronic properties and absorption spectra of the complexes, TD-DFT calculations were executed for phenoxyl radical complexes considering triplet as well as singlet spin states. Alcohol oxidation was examined utilizing complexes 16 as catalyst, and importance of stabilization of Cu(I) intermediate was scrutinized and generation of Cu(II)–OOH was examined. Catalytic promiscuity for catechol oxidase and phenoxazinone synthase activity by complexes (15) was investigated. Theoretical calculations and ESI–MS spectral studies were performed during oxidation chemistry of benzyl alcohol, catechol and o-amino phenol to support the proposed mechanism.


Datum: 20.01.2020


Two cubane-like [M 4 O 4 ] {M = nickel(II), cobalt(II)} complexes: syntheses, crystal structures and magnetic properties

Abstract

Two cubane-like complexes, namely [Ni4L4(HOEt)4] (1), [Co4L4(HOEt)4] (2) (H2L = (E)-2-((3-hydroxypropylimino)methyl)-6-methoxyphenol), were prepared under solvothermal conditions. Structural analyses show that complexes 12 are tetranuclear complexes with a cubane topology in which four M atoms and four µ3-O atoms occupy the alternate vertices of the cubane. The magnetic properties of them have been investigated. Antiferromagnetic interactions were observed for complexes 1 and 2.


Datum: 11.01.2020


Structure and magnetic properties of a serendipitously synthesized copper(II) complex: [Cu(3-Br-2-pyone) 6 ](ClO 4 ) 2

Abstract

Hexakis(3-bromo-2(1H)-pyridone)copper(II) perchlorate was prepared. Crystals and powdered bulk samples were characterized using IR, single-crystal and powder X-ray diffraction, combustion analysis, EPR and temperature-dependent magnetic susceptibility data. The complex crystallizes in the triclinic space group P\(\bar{1}\) and comprises a Jahn–Teller distorted Cu(II)–O6 coordination sphere with the ligands coordinated via the pyridone O-atoms. EPR and variable temperature susceptibility measurements show that the complex is well isolated magnetically in the lattice.


Datum: 01.01.2020


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: 01.01.2020


Synthesis, crystal structure and properties of copper(II) complexes with triethanolamine and carboxylic acids (succinic, salicylic, cinnamic)

Abstract

The interaction of triethanolamine (TEA) with Cu(II) salts of salicylic, cinnamic and succinic acids was studied for the first time. The structure of the synthesized complexes was investigated by single-crystal X-ray diffraction. TEA complexes with Cu(II) salicylate (1) and cinnamate (2) are binuclear mixed ligand complexes, but interaction of TEA with Cu(II) succinate leads to the formation of cationic mononuclear complex—[Cu(TEA)2](C4H4O4) (3). Cu(II) complexes 13 were also characterized by physicochemical and spectroscopic methods. Their antimicrobial activity was investigated.


Datum: 01.01.2020


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: 01.01.2020


Coordination mode of cyclohex-1-enylolonium cation and bridging pyridyl derivatives as gem -diol chelates to rhenium(I) and (VII)

Abstract

Rhenium(I) and (VII) complexes with cyclohex-1-enylolonium cation and bridging pyridyl derivatives are reported. Additionally, the CO-bridged pyridyl and their related compounds have shown interesting behaviour in their reactivity towards compounds containing two amino groups. The unusual cationic compound: (2,6-diaza-cyclohex-1-enylolonium)2-aza-benzoate (H2den), was isolated from the reaction mixture of 1,2-di(pyridin-2-yl)ethane-1,2-dione with propane-1,3-diamine in methanol. The latter ligand: H2den, was used in the synthesis of rhenium(I) complex in its reaction with [Re(CO)5Cl] that gave rise to novel rhenium(I) complex fac-[Re(CO)3(Hhdm)] (1). The surprising aspect in the formation of (1) is the modification of H2den which was stabilized into a coordinated six-membered pyrimidine ring, 1,4,5,6-tetrahydropyrimidin-2-yl)di(pyridin-2-yl)methanol (H2hdm) chelate. The derived ligand acts as a tridentate monoanionic N2,O-donor ligand towards the fac-[Re(CO)3]+ core. Surprisingly, the 2-aza-benzoate counter-ion that was present in the used ligand is not displayed in the crystal structure of complex 1, and might have been stabilized into 2-aza-benzoic acid (picolinic acid). The reaction of the potential tridentate N2,O-donor ligand 2,2′-dipyridylketone (dpk) with trans-[ReOI2(OEt)(PPh3)2] led to the isolation of [ReO3(dpk·OH)] (2). The ligand H2den and the rhenium complexes were spectroscopically characterized, and the structures of H2den, 1 and 2 were established by X-ray diffraction.


Datum: 01.01.2020


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: 01.01.2020


 


Category: Current Chemistry Research

Last update: 28.03.2018.






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