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Synthesis, Characterization, and Catalytic Activity of Organometallic Complexes 2022
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Synthesis, Characterization, and Catalytic Activity of Organometallic Complexes 2022

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Organometallic Chemistry".

Deadline for manuscript submissions: closed (31 October 2022) | Viewed by 8934

Special Issue Editor

Dr. Jacek Nycz

E-Mail Website
Guest Editor
Institute of Chemistry, Faculty of Science and Technology, University of Silesia in Katowice, ul. Szkolna 9, 40-007 Katowice, Poland
Interests: synthesis of organic and organometallic compounds; organic and organometallic chemistry; organophosphorus chemistry; N-hetero-organic compounds
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The increasing use of organometallic complexes as catalysts in organic syntheses carried out in a homogeneous frame requires them to have determined properties. To be hydrocarbon-soluble, the metal must be surrounded by lipophilic fragments that must be bulky to offer protection to the coordinated unsaturated active metal site. Moreover, this steric cage gives kinetic stabilization to both intramolecular and associative processes as a solvent or other ligand coordination. To reduce this opportunity, it is also helpful that the ligand ends with an abundance of methyl groups. Another essential feature conferring stability to the ligand is to be void of b-hydrogen, thus avoiding the possibility of a b-hydrogen decomposition pathway for the metal compound. All these properties are matched by an appropriate choice of ligand(s) for the metal complexes.

In chemistry mediated by metal complexes by subtle changes in ligand design, it is possible to alter the reactivity vastly and thus alter the catalytic properties of the complexes; examples include variation in a variety of protecting groups in catalytically useful transition metal complexes. Changing the substituents' nature makes it possible to introduce chiral centers, which are crucial in polymers' stereoselective synthesis.

Applications of supported bimetallic clusters are most likely in the production of specialty chemicals or with stable combinations of oxophilic and noble metals. Supported metals are among the essential catalysts used in technology, and, increasingly, these are bimetallic, usually incorporating at least one metal from the platinum group. Supported bimetallic catalysts used in large-scale processes include the Re–Pt, Sn–Pt, and Ir–Pt catalysts for naphtha reforming and the Rh–Pt and other catalysts for the conversion of automobile exhausts. The catalytic behavior of a supported metal is influenced by the size of the metal particles and by their interactions with the support and other catalyst components, such as a second catalytic metal, which could be a promoter. The second metal may influence the first metal through electronic interactions or be involved in the reaction by bonding directly to reactants or intermediates. Often, the interactions between the two metals are complex and largely unknown, and consequently, there are excellent opportunities for preparing bimetallic catalysts with new properties.

Several industrial processes such as the ammoxidation of propene to acrylonitrile, olefin epoxidation, and olefin metathesis reactions are carried out over organometallic catalysts.

This Special Issue welcomes the submission of papers based on original research or reviews that describe innovative sustainable organic or organometallic reactions, methodologies, and their applications, ranging from mechanistic aspects, or, in application in catalysis, the immobilization of the complexes into mesoporous materials.

Dr. Jacek Nycz
Guest Editor

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Keywords

  • catalytic activity
  • turnover number (abbreviated TON)
  • synthesis and reactivity
  • electrochemistry
  • spectroscopy
  • reaction mechanism
  • structural and spectroscopic characterization

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Published Papers (4 papers)

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Research

17 pages, 2552 KiB  
Article
Interaction between [(η6-p-cym)M(H2O)3]2+ (MII = Ru, Os) or [(η5-Cp*)M(H2O)3]2+ (MIII = Rh, Ir) and Phosphonate Derivatives of Iminodiacetic Acid: A Solution Equilibrium and DFT Study
by Linda Bíró, Botond Tóth, Norbert Lihi, Etelka Farkas and Péter Buglyó
Molecules 2023, 28(3), 1477; https://doi.org/10.3390/molecules28031477 - 3 Feb 2023
Cited by 2 | Viewed by 1459
Abstract
The pH-dependent binding strengths and modes of the organometallic [(η6-p-cym)M(H2O)3]2+ (MII = Ru, Os; p-cym = 1-methyl-4-isopropylbenzene) or [(η5-Cp*)M(H2O)3]2+ (MIII = Rh, Ir; Cp* [...] Read more.
The pH-dependent binding strengths and modes of the organometallic [(η6-p-cym)M(H2O)3]2+ (MII = Ru, Os; p-cym = 1-methyl-4-isopropylbenzene) or [(η5-Cp*)M(H2O)3]2+ (MIII = Rh, Ir; Cp* = pentamethylcyclopentadienyl anion) cations towards iminodiacetic acid (H2Ida) and its biorelevant mono- and diphosphonate derivatives N-(phosphonomethyl)-glycine (H3IdaP) and iminodi(methylphosphonic acid) (H4Ida2P) was studied in an aqueous solution. The results showed that all three of the ligands form 1:1 complexes via the tridentate (O,N,O) donor set, for which the binding mode was further corroborated by the DFT method. Although with IdaP3− and Ida2P4− in mono- and bis-protonated species, where H+ might also be located at the non-coordinating N atom, the theoretical calculations revealed the protonation of the phosphonate group(s) and the tridentate coordination of the phosphonate ligands. The replacement of one carboxylate in Ida2− by a phosphonate group (IdaP3−) resulted in a significant increase in the stability of the metal complexes; however, this increase vanished with Ida2P4−, which was most likely due to some steric hindrance upon the coordination of the second large phosphonate group to form (5 + 5) joined chelates. In the phosphonate-containing systems, the neutral 1:1 complexes are the major species at pH 7.4 in the millimolar concentration range that is supported by both NMR and ESI-TOF-MS. Full article
(This article belongs to the Special Issue Synthesis, Characterization, and Catalytic Activity of Organometallic Complexes 2022)
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19 pages, 4443 KiB  
Article
Rhenium Tricarbonyl Complexes of Azodicarboxylate Ligands
by Rose Jordan, Maryam Niazi, Sascha Schäfer, Wolfgang Kaim and Axel Klein
Molecules 2022, 27(23), 8159; https://doi.org/10.3390/molecules27238159 - 23 Nov 2022
Cited by 4 | Viewed by 2179
Abstract
The excellent π-accepting azodicarboxylic esters adcOR (R = Et, iPr, tBu, Bn (CH2-C6H5) and Ph) and the piperidinyl amide derivative adcpip were used as bridging chelate ligands in dinuclear Re(CO)3 complexes [{Re(CO)3Cl} [...] Read more.
The excellent π-accepting azodicarboxylic esters adcOR (R = Et, iPr, tBu, Bn (CH2-C6H5) and Ph) and the piperidinyl amide derivative adcpip were used as bridging chelate ligands in dinuclear Re(CO)3 complexes [{Re(CO)3Cl}2(µ-adcOR)] and [{Re(CO)3Cl}2(µ-adcpip)]. From the adcpip ligand the mononuclear derivatives [Re(CO)3Cl(adcpip)] and [Re(CO)3(PPh3)(µ-adcpip)]Cl were also obtained. Optimised geometries from density functional theory (DFT) calculations show syn and anti isomers for the dinuclear fac-Re(CO)3 complexes at slightly different energies but they were not distinguishable from experimental IR or UV–Vis absorption spectroscopy. The electrochemistry of the adc complexes showed reduction potentials slightly below 0.0 V vs. the ferrocene/ferrocenium couple. Attempts to generate the radicals [{Re(CO)3Cl}2(µ-adcOR)]•− failed as they are inherently unstable, losing very probably first the Cl− coligand and then rapidly cleaving one [Re(CO)3] fragment. Consequently, we found signals in EPR very probably due to mononuclear radical complexes [Re(CO)3(solv)(adc)]•. The underlying Cl−→solvent exchange was modelled for the mononuclear [Re(CO)3Cl(adcpip)] using DFT calculations and showed a markedly enhanced Re-Cl labilisation for the reduced compared with the neutral complex. Both the easy reduction with potentials ranging roughly from −0.2 to −0.1 V for the adc ligands and the low-energy NIR absorptions in the 700 to 850 nm range place the adc ligands with their lowest-lying π* orbital being localised on the azo function, amongst comparable bridging chelate N^N coordinating ligands with low-lying π* orbitals of central azo, tetrazine or pyrazine functions. Comparative (TD)DFT-calculations on the Re(CO)3Cl complexes of the adcpip ligand using the quite established basis set and functionals M06-2X/def2TZVP/LANL2DZ/CPCM(THF) and the more advanced TPSSh/def2-TZVP(+def2-ECP for Re)/CPCMC(THF) for single-point calculations with BP86/def2-TZVP(+def2-ECP for Re)/CPCMC(THF) optimised geometries showed a markedly better agreement of the latter with the experimental XRD, IR and UV–Vis absorption data. Full article
(This article belongs to the Special Issue Synthesis, Characterization, and Catalytic Activity of Organometallic Complexes 2022)
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21 pages, 6322 KiB  
Article
Selective Oxidation of Glycerol via Acceptorless Dehydrogenation Driven by Ir(I)-NHC Catalysts
by M. Victoria Jiménez, Ana I. Ojeda-Amador, Raquel Puerta-Oteo, Joaquín Martínez-Sal, Vincenzo Passarelli and Jesús J. Pérez-Torrente
Molecules 2022, 27(22), 7666; https://doi.org/10.3390/molecules27227666 - 8 Nov 2022
Cited by 4 | Viewed by 2272
Abstract
Iridium(I) compounds featuring bridge-functionalized bis-NHC ligands (NHC = N-heterocyclic carbene), [Ir(cod)(bis-NHC)] and [Ir(CO)2(bis-NHC)], have been prepared from the appropriate carboxylate- or hydroxy-functionalized bis-imidazolium salts. The related complexes [Ir(cod)(NHC)2]+ and [IrCl(cod)(NHC)(cod)] have been synthesized from a 3-hydroxypropyl functionalized imidazolium [...] Read more.
Iridium(I) compounds featuring bridge-functionalized bis-NHC ligands (NHC = N-heterocyclic carbene), [Ir(cod)(bis-NHC)] and [Ir(CO)2(bis-NHC)], have been prepared from the appropriate carboxylate- or hydroxy-functionalized bis-imidazolium salts. The related complexes [Ir(cod)(NHC)2]+ and [IrCl(cod)(NHC)(cod)] have been synthesized from a 3-hydroxypropyl functionalized imidazolium salt. These complexes have been shown to be robust catalysts in the oxidative dehydrogenation of glycerol to lactate (LA) with dihydrogen release. High activity and selectivity to LA were achieved in an open system under low catalyst loadings using KOH as a base. The hydroxy-functionalized bis-NHC catalysts are much more active than both the carboxylate-functionalized ones and the unbridged bis-NHC iridium(I) catalyst with hydroxyalkyl-functionalized NHC ligands. In general, carbonyl complexes are more active than the related 1,5-cyclooctadiene ones. The catalyst [Ir(CO)2{(MeImCH2)2CHOH}]Br exhibits the highest productivity affording TONs to LA up to 15,000 at very low catalyst loadings. Full article
(This article belongs to the Special Issue Synthesis, Characterization, and Catalytic Activity of Organometallic Complexes 2022)
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12 pages, 16356 KiB  
Article
Redox-Active Metal-Organic Frameworks with Three-Dimensional Lattice Containing the m-Tetrathiafulvalene-Tetrabenzoate
by Hongrui Huang, Zhi-Mei Yang, Xiao-Cheng Zhou, Gen Zhang and Jian Su
Molecules 2022, 27(13), 4052; https://doi.org/10.3390/molecules27134052 - 23 Jun 2022
Cited by 2 | Viewed by 2327
Abstract
Metal-organic frameworks (MOFs) constructed by tetrathiafulvalene-tetrabenzoate (H4TTFTB) have been widely studied in porous materials, while the studies of other TTFTB derivatives are rare. Herein, the meta derivative of the frequently used p-H4TTFTB ligand, m-H4TTFTB, and [...] Read more.
Metal-organic frameworks (MOFs) constructed by tetrathiafulvalene-tetrabenzoate (H4TTFTB) have been widely studied in porous materials, while the studies of other TTFTB derivatives are rare. Herein, the meta derivative of the frequently used p-H4TTFTB ligand, m-H4TTFTB, and lanthanide (Ln) metal ions (Tb3+, Er3+, and Gd3+) were assembled into three novel MOFs. Compared with the reported porous Ln-TTFTB, the resulted three-dimensional frameworks, Ln-m-TTFTB ([Ln2(m-TTFTB)(m-H2TTFTB)0.5(HCOO)(DMF)]·2DMF·3H2O), possess a more dense stacking which leads to scarce porosity. The solid-state cyclic voltammetry studies revealed that these MOFs show similar redox activity with two reversible one-electron processes at 0.21 and 0.48 V (vs. Fc/Fc+). The results of magnetic properties suggested Dy-m-TTFTB and Er-m-TTFTB exhibit slow relaxation of the magnetization. Porosity was not found in these materials, which is probably due to the meta-configuration of the m-TTFTB ligand that seems to hinder the formation of pores. However, the m-TTFTB ligand has shown to be promising to construct redox-active or electrically conductive MOFs in future work. Full article
(This article belongs to the Special Issue Synthesis, Characterization, and Catalytic Activity of Organometallic Complexes 2022)
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