Organotransition Metal Research Articles

Synthesis, Structure, and Optical Property of Tris(biaryldiyl)metal Complexes Consisting of Group 9 Elements.

We report the synthesis and characterization of tris(biphenyl-2,2'-diyl)metal complexes of trivalent group 9 elements (1M, M = Co, Rh, Ir) and their nonplanarly π-extended analogs, tris(1,1'-binaphthyl-2,2'-diyl)metal complexes (2M, M = Rh, Ir). Single crystal X-ray crystallography reveals the distorted octahedral geometry with an approximate C3 symmetry of trianionic complexes 1M (M = Co, Rh, Ir) and 2M (M = Rh, Ir), which are contacted by three Li+ ions in the crystal. Complex 1Ir exhibits yellow luminescence in THF with a photoluminescence quantum yield (ΦPL) of up to 0.73, along with a distinctive photophysical property, namely, a concentration dependence of the emission wavelength from 530 to 580 nm. This is a characteristic property of 1Ir and has not been observed in its isoelectronic analog, tris(2-phenylpyridinato)iridium(III) (Ir(ppy)3). The concentration-dependent optical properties originate from the dissociation equilibria of Li+ ions from the anionic chromophore. Complex 2Ir also exhibits luminescence at 715 nm in THF, with a notable bathochromic shift from 1Ir through the π-extension. The findings offer insights into the photophysical properties of homoleptic organo-transition metal complexes, providing the foundation for the design of related transition metal complexes.

Learning organo-transition metal catalyzed reactions by graph neural networks.

Chemical reaction outcome prediction presents a fundamental challenge in synthetic chemistry. Most existing machine learning (ML) approaches focus on chemical reactions of typical elements. We developed a simple ML model focused on organo-transition metal-catalyzed reactions (OMCRs). Instead of overall reactions observed in experiments, we let the ML model learn the sequence of simplified elementary reactions. This drastically reduced the complexity of the model and helped it find common patterns from distinct reactions. We let a graph neural network learn the reactivity index of a pair of atoms. The model was able to learn a wide variety of OMCRs, and the accuracy of reaction prediction reached 97%, even though the model has extremely fewer learnable parameters than other standards. The learned reactivity indices of bonds nicely summarize the knowledge of reactions in the dataset.

Isolation and Structures of Polyarene Palladium Nanoclusters.

We report that surrounding coordination of neutral six-membered arene rings affords molecularly well-defined organotransition metal nanoclusters. With the use of [2.2]paracyclophane as the face-capping arene ligand, we have isolated two polyarene palladium nanoclusters, one consisting of a hexakis-arene ligand shell and a hexagonal close-packed Pd13 anticuboctahedron trichloride core, and the other consisting of an octakis-arene ligand shell and a non-close-packed Pd17 square gyrobicupola dichloride core, both with Pd-Pd direct bonding. The μ4-facial coordination mode of arene was discovered through the structural characterization of the Pd13 cluster. Their Pd13 and Pd17 cores, which are distinct from the previously identified face-centered-cubic Pd13 core surrounded by seven-membered cycloheptatrienyl, are explained by stereochemical and theoretical analyses.

Frontispiece: Large Isotope Effects in Organometallic Chemistry

Hydrogen atoms sometimes react far faster than deuterium atoms. Reactions can proceed over 100 times faster with hydrogen, or the deuterium reaction may not be observed at all. Examples of large kinetic isotope effects throughout organotransition metal chemistry are reviewed. Possible causes for these observed effects are discussed, including vibrational differences, multistep reactions, and proton tunneling. Artwork depicting a hydrogen cheetah and a deuterium sloth by Caitlyn Y. Tong. Read more in the Minireview by M. A. Bowring et al. on page 14800 ff.

Targeted Antibacterial Strategy Based on Reactive Oxygen Species Generated from Dioxygen Reduction Using an Organoruthenium Complex.

Pathogenic microorganisms pose a serious threat to global public health due to their persistent adaptation and growing resistance to antibiotics. Alternative therapeutic strategies are required to address this growing threat. Bactericidal antibiotics that are routinely prescribed to treat infections rely on hydroxyl radical formation for their therapeutic efficacies. We developed a redox approach to target bacteria using organotransition metal complexes to mediate the reduction of cellular O2 to H2O2, as a precursor for hydroxyl radicals via Fenton reaction. We prepared a library of 480 unique organoruthenium Schiff-base complexes using a coordination-driven three-component assembly strategy and identified the lead organoruthenium complex Ru1 capable of selectively invoking oxidative stress in Gram-positive bacteria, in particular methicillin-resistant Staphylococcus aureus, via transfer hydrogenation reaction and/or single electron transfer on O2. This strategy paves the way for a targeted antimicrobial approach leveraging on the redox chemistry of organotransition metal complexes to combat drug resistance.

The Power of Organotransition Metal Catalysis in Synthesizing Organic Molecules

ADVERTISEMENT RETURN TO ISSUEEditor's PageNEXTThe Power of Organotransition Metal Catalysis in Synthesizing Organic MoleculesTianning Diao*Tianning Diao*Email: [email protected]More by Tianning DiaoView Biographyhttps://orcid.org/0000-0003-3916-8372, Liang DengLiang DengMore by Liang DengView Biographyhttps://orcid.org/0000-0002-0964-9426, and Wenjun TangWenjun TangMore by Wenjun TangView Biographyhttps://orcid.org/0000-0002-8209-4156Cite this: Organometallics 2021, 40, 14, 2179–2181Publication Date (Web):July 26, 2021Publication History Published online26 July 2021Published inissue 26 July 2021https://doi.org/10.1021/acs.organomet.1c00361Copyright © Published 2021 by American Chemical SocietyRIGHTS & PERMISSIONSArticle Views676Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (3 MB) Get e-AlertsSUBJECTS:Palladium,Metals,Catalysts,Reactivity,Cross coupling reaction Get e-Alerts

Cyclooctadiene Rh(I) Bis- and Tris(pyrazolyl)aluminate Complexes and Their Catalytic Activity on the Polymerization of Phenylacetylene.

In this work, we report the transfer of alkyl bis- and tris(pyrazolyl)aluminates metalloligands to an electron-rich organotransition metal center. The 16-electron heterobimetallic complexes of rhodium [Rh(COD){Al(Ph2pz)2Me2}] (3) and [Rh(COD){Al(Ph2pz)3Me}] (4) were obtained by metathesis reaction of the sodium bis- (1) and tris(pyrazolyl)aluminate (2) with [RhCl(COD)]2. For 3, 1H and 13C NMR in solution along with DFT calculations are consistent with a κ2-coordination mode of the bis(pyrazolyl)aluminate to a square-planar Rh(I) center. The X-ray structure of 4 shows a similar κ2-coordination mode of the tris(pyrazolyl)aluminate to Rh(I) with a pendant pyrazolyl moiety. The attempted synthesis of aluminate-rhodium complexes with R = CF3, tBu on the pyrazolate ring afforded [Rh(R2pz)(COD)]2 and [R2pzAlMe2]2. Complexes 3 and 4 were investigated as homogeneous catalysts in the polymerization of phenylacetylene (PA). Both complexes showed enhanced catalytic activity compared to analogous rhodium poly(pyrazolyl)borates. Optimized gas-phase DFT geometries of 3, 4, [Rh(COD){B(Ph2pz)2Me2}], and [Rh(COD){B(Ph2pz)3Me}] were used to compare bite angles, while DFT geometries of 3-CO, 4-CO, [Rh(CO)2{B(Ph2pz)2Me2}], and [Rh(CO)2{B(Ph2pz)3Me}] were employed to probe the electronic situation of the rhodium center through IR CO stretching modes. The wider bite angles and the less electron-rich rhodium center of the poly(pyrazolyl)aluminates compared with their borate analogues could be implicated in the better performance of the active catalytic species during polymerization of PA.

Brice Bosnich. 3 June 1936—13 April 2015

Brice Bosnich, an Australian inorganic chemist, graduated from the University of Sydney and obtained his PhD at the Australian National University, Canberra. He then worked successively at University College London, the University of Toronto and the University of Chicago. He had an abiding interest in stereochemistry and its relationship with chemical reactivity, and in the chirality and optical activity of coordination and organometallic complexes, mainly those of the d-block elements. His early studies concerned the topological and conformational behaviour of classical coordination compounds, mainly of cobalt(III), and made extensive use of the technique of circular dichroism. He put this background to elegant use in perhaps his most distinctive work, namely, the design and synthesis of a C 2 -symmetric ditertiary phosphine, ( S , S )-chiraphos, the rhodium(I) complex [Rh{Ph 2 PCH(CH 3 )CH(CH 3 )PPh 2 }] + of which catalysed efficiently the homogeneous hydrogenation of prochiral enamides to amino acids in high optical purity. Bosnich traced the high enantioselectivity to the chiral array of P-phenyl substituents that is generated on coordination of ( S , S )-chiraphos. In principle, catalytic enantioselective synthesis represents a powerful and economic method of introducing chirality into the synthesis of biologically active molecules, which, since the thalidomide tragedy, are required to be marketed only in optically pure forms. Dissymmetric ligands similar to ( S , S )-chiraphos are now routinely employed in this type of synthesis. Bosnich developed several other enantioselective processes based on organo-transition metal chemistry. He also had several quasi-theoretical interests, including the possible use of circular dichroism to determine the absolute configuration of chiral metal complexes, and the development of a molecular mechanics force field for metallocenes. He maintained a strong interest in the properties of multimetallic proteins and devoted much effort to the construction of chiral binucleating ligands. During the 7–8 years before his retirement from the University of Chicago in 2006, he shifted his research to supramolecular recognition by suitably designed metal complexes.

The roles of Lewis acidic additives in organotransition metal catalysis.

We describe recent examples of prominent reactions in organic synthesis that involve transition metal and Lewis acid cocatalysts. Introducing Lewis acid additives to transition metal catalysis can enable new reactivity or improve activity and selectivity of an existing process. Several studies are highlighted to illustrate the possible roles of Lewis acids in catalytic mechanisms. The uses of Lewis acid additives in bond-breaking catalysis (C-C activation, C-H activation, and hydrogenolysis reactions) and bond-forming catalysis (Au-catalysed alkyne functionalisation, Pd-catalysed C-C and C-N bond formation) are reviewed.

Investigation on the photophysical properties of a series of promising phosphorescent iridium (III) complexes with modified cyclometalating ligands

Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) were applied to investigate the electronic structures and photophysical properties of a series of phosphorescent iridium (III) complexes, [(C∧N)2Ir(N∧N)]+(PF6)−, in which C∧N = 4-aryl-1-benzyl-1H-1, 2, 3-triazoles. Herein, aryl = phenyl, biphenyl, three-phenyl aromatic for complexes 1a, 2a, 3a (N∧N = 2, 2′-bipyridine) and aryl = 4′, 6′-difluorophenyl, 6′-fluoro-biphenyl, 6′-fluoro-three-phenyl aromatic for complexes 1b, 2b, 3b (N∧N = 4, 4′-di-tert-butyl-2, 2′-bipyridine), respectively. The geometric/electronic configurations, absorption/emission properties and phosphorescent performances have been outlined for each of the complexes. Based on the two simplifications presented in this paper and the available experimental data, the phosphorescent radiative rates for complexes 1a-3b were approximately obtained to be: 1.20 × 106 s−1, 1.68 × 105 s−1, 2.19 × 107 s−1, 3.85 × 106 s−1, 1.85 × 107 s−1 and 1.50 × 107 s−1, respectively. In view of the electroluminescent applications in OLED, our present research work is of great importance for the design and synthesis of organo-transition metal complexes with improved phosphorescent performances.

Surface Organometallic Chemistry of Supported Iridium(III) as a Probe for Organotransition Metal–Support Interactions in C–H Activation

Systematic study of the interactions between organometallic catalysts and metal oxide support materials is essential for the realization of rational design in heterogeneous catalysis. Herein we describe the stoichiometric and catalytic chemistry of a [Cp*(PMe3)Ir(III)] complex chemisorbed on a variety of acidic metal oxides as a multifaceted probe for stereoelectronic communication between the support and organometallic center. Electrophilic bond activation was explored in the context of stoichiometric hydrogenolysis as well as catalytic H/D exchange. Further information was obtained from the observation of processes related to dynamic exchange between grafted organometallic species and those in solution. The supported organometallic species were characterized by a variety of spectroscopic techniques including dynamic nuclear polarization-enhanced solid-state NMR spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy, and X-ray absorption spectroscopy. Strongly acidic modified metal oxi...

Cationic Two-Coordinate Complexes of Pd(I) and Pt(I) Have Longer Metal-Ligand Bonds Than Their Neutral Counterparts

Summary One-electron oxidation of known ( t Bu 3 P) 2 M (1, M = Pd; 2, M = Pt) with [Ph 3 C][HCB 11 Cl 11 ] leads to two-coordinate, monovalent cations of the formula [( t Bu 3 P) 2 M][HCB 11 Cl 11 ] (3, M = Pd; 4, M = Pt), which also possess linear geometry but with elongated M–P bonds. Spectroscopic and computational studies consistently show that the unpaired electron of the d 9 configuration of 3 and 4 belongs to largely non-bonding orbitals: the s/d z2 hybrid for Pd and the degenerate d x2-y2 /d xy pair for Pt. We show that molecular-orbital-based arguments alone are incapable of predicting or rationalizing the observed M–P bond lengthening on oxidation; correct prediction and rationalization are achieved only by inclusion of electrostatic and Pauli effects. This emphasizes the dangers of interpreting any perturbative changes in bond metrics solely on the basis of energies and occupancies of molecular orbitals; the inclusion of electrostatic and Pauli components is essential to providing a more complete picture.

Boron-mediated sequential alkyne insertion and C-C coupling reactions affording extended π-conjugated molecules.

C–C bond coupling reactions illustrate the wealth of organic transformations, which are usually mediated by organotransition metal complexes. Here, we show that a borafluorene with a B–Cl moiety can mediate sequential alkyne insertion (1,2-carboboration) and deborylation/Csp2–Csp2 coupling reactions, leading to aromatic molecules. The first step, which affords a borepin derivative, proceeds very efficiently between the borafluorene and various alkynes by simply mixing these two components. The second step is triggered by a one-electron oxidation of the borepin derivative, which results in the formation of a phenanthrene framework. When an excess amount of oxidant is used in the second step, the phenanthrene derivatives can be further transformed in situ to afford dibenzo[g,p]chrysene derivatives. The results presented herein will substantially expand the understanding of main group chemistry and provide a powerful synthetic tool for the construction of a wide variety of extended π-conjugated systems.

ChemInform Abstract: Anionic N‐Heterocyclic Carbenes: Synthesis, Coordination Chemistry and Applications in Homogeneous Catalysis

AbstractReview: 304 refs.

有機金属化学の基礎から最近の進歩まで

Homogeneous catalyses promoted by transition metal complexes such as cross coupling reaction, Mizoroki-Heck reaction, Tsuji-Trost allylation reaction，functionalization of C-H bond, Sharpless oxidation reaction, and some recent topics related to organotransition metal complexes are described. Mechanistic aspects of these reactions are also discussed based on the fundamental reaction patterns of organotransiton metal complexes. Future perspectives of organotransition metal catalyzed reactions are also described.

Generation, Characterization, and Tunable Reactivity of Organometallic Fragments Bound to a Protein Ligand.

Organotransition metal complexes catalyze important synthetic transformations, and the development of these systems has rested on the detailed understanding of the structures and elementary reactions of discrete organometallic complexes bound to organic ligands. One strategy for the creation of new organometallic systems is to exploit the intricate and highly structured ligands found in natural metalloproteins. We report the preparation and characterization of discrete rhodium and iridium fragments bound site-specifically in a κ(2)-fashion to the protein carbonic anhydrase as a ligand. The reactions of apo human carbonic anhydrase with [Rh(nbd)2]BF4 or [M(CO)2(acac)] (M=Rh, Ir) form proteins containing Rh or Ir with organometallic ligands. A colorimetric assay was developed to quantify rapidly the metal occupancy at the native metal-binding site, and (15)N-(1)H NMR spectroscopy was used to establish the amino acids to which the metal is bound. IR spectroscopy and EXAFS revealed the presence and number of carbonyl ligands and the number total ligands, while UV-vis spectroscopy provided a signature to readily identify species that had been fully characterized. Exploiting these methods, we observed fundamental stoichiometric reactions of the artificial organometallic site of this protein, including reactions that simultaneously form and cleave metal-carbon bonds. The preparation and reactivity of these artificial organometallic proteins demonstrate the potential to study a new genre of organometallic complexes for which the rates and outcomes of organometallic reactions can be controlled by genetic manipulation of the protein scaffold.

ChemInform Abstract: Electrophilic Halogenation‐Reductive Elimination Chemistry of Organopalladium and ‐Platinum Complexes

AbstractReview: 59 refs.

Electrophilic halogenation-reductive elimination chemistry of organopalladium and -platinum complexes.

CONSPECTUS: Transition metal-catalyzed organic transformations often reveal competing reaction pathways. Determining the factors that control the selectivity of such reactions is of extreme importance for the design of reliable synthetic protocols. Herein, we present the account of our studies over the past decade aimed at understanding the selectivity of reductive elimination chemistry of organotransition metal complexes under electrophilic halogenation conditions. Much of our effort has focused on finding the conditions for selective formation of carbon (aryl)-halogen bonds in the presence of competing C-C reductive elimination alternatives. In most cases, the latter was the thermodynamically preferred pathway; however, we found that the reactions could be diverted toward the formation of aryl-iodine and aryl-bromine bonds under kinetic conditions. Of particular importance was to maintain the complex geometry that prohibits C-C elimination while allowing for the elimination of carbon-halogen bonds. This was achieved by employing sterically rigid diphosphine ligands which prevented isomerization within a series of Pt(IV) complexes. It was also important to understand that the neutral M(IV) products often observed or isolated in the oxidative addition reactions are not necessarily the intermediates in the reductive elimination chemistry as it generally takes place from unsaturated species formed en route to relatively stable M(IV) complexes. While aryl-halide reductive elimination for heavier halogens can be competitive with aryl-aryl coupling in diaryl M(IV) complexes, the latter reaction always prevails over aryl-fluoride bond formation. Even when one of the aryl groups is a part of a rigid cyclometalated ligand C-C coupling is still the dominant reaction pathway. However, when one of the aryl groups is replaced with a phenolate donor aryl-F bond formation becomes preferred over C-O bond elimination. During our studies, other interesting reactions have been discovered. For example, the fluorination of the C(sp(3))-H bond can be very selective and compete favorably with C-C coupling. Also, in electron-poor complexes, metal oxidation can have higher energy than oxidation of the coordinated iodo ligand resulting in I-F elimination instead of the formation of aryl-I bond. Overall, electrophilic fluorination can lead to often very selective elimination reactions giving new C-C, C-I, C-F, or I-F bonds, with this selectivity dependent on the metal center, supporting ligands, complex geometry, and electrophilic fluorine source. Together with the many reports on the halogenation of organometallic compounds that appeared in recent years, our results contribute to understanding the requirements for selective transformations under electrophilic conditions and design of new synthetic methods for making organohalogen compounds.

Investigation of Organoiron Catalysis in Kumada–Tamao–Corriu-Type Cross-Coupling Reaction Assisted by Solution-Phase X-ray Absorption Spectroscopy

Abstract Solution-phase synchrotron X-ray absorption spectroscopy (XAS) is a powerful tool for structural and mechanistic investigations of paramagnetic organoiron intermediates in solution-phase reactions. For paramagnetic organotransition metal intermediates, difficulties are often encountered with conventional NMR- and EPR-based analyses. By using solution-phase XAS, we succeeded in identifying the organoiron species formed in the reaction of iron bisphosphine with mesitylmagnesium bromide, MesMgBr, and 1-bromodecane in a [FeX2(SciOPP)]-catalyzed Kumada–Tamao–Corriu (KTC)-type cross-coupling reaction. X-ray absorption near-edge structure (XANES) spectra showed that the resulting aryliron species possessed a divalent oxidation state. Extended X-ray absorption fine structure (EXAFS) demonstrated that the solution-phase molecular geometries of these species are in satisfactory agreement with the crystallographic geometries of [FeIIBrMes(SciOPP)] and [FeIIMes2(SciOPP)]. By combining GC-quantitative analysis and solution-phase XAS, the cross-coupling reactivities of these aryliron species were successfully investigated in the reaction with 1-bromodecane under stoichiometric and catalytic conditions.

Charge-transfer excited states in phosphorescent organo-transition metal compounds: a difficult case for time dependent density functional theory?

A series of 17 platinum(ii) and iridium(iii) complexes have been investigated theoretically and experimentally to elucidate the charge-transfer character in emission from the lowest triplet state. TDDFT is found to be surprisingly accurate.