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We synthesized two 4Me−PNP ligands which block metal-ligand cooperation (MLC) with the Ru center and compared their Ru complex chemistry to their two traditional analogues used in acceptorless alcohol dehydrogenation catalysis. The corresponding 4Me−PNP complexes, which do not undergo dearomatization upon addition of base, allowed us to obtain rare, albeit unstable, 16 electron mono-CO Ru(0) complexes. Reactivity with CO and H2 allows for stabilization and extensive characterization of bis-CO Ru(0) 18 electron and Ru(II) cis and trans dihydride species that were also shown to be capable of C(sp2) −H activation. Reactivity and catalysis are contrasted to non-methylated Ru(II) species, showing that an MLC pathway is not necessary, with dramatic differences in outcomes during catalysis between iPr and tBu PNP complexes within each of the 4Me and non-methylated backbone PNP series being observed. Unusual intermediates are characterized in one of the new and one of the traditional complexes, and a common catalysis deactivation pathway was identified., source:https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202103778

We report a series of heterobimetallic Pt/Zn and Pt/Ca complexes to study the effect of proximity of a dicationic base metal on the organometallic Pt species. Varying degrees of Pt⋅⋅⋅Zn and Zn interaction with the bridging Me group are achieved, showcasing snapshots of a hypothetical process of retrotransmetalation from Pt to Zn. In contrast, only weak interactions were observed for Ca with a Pt-bound Me group. Activation of H2, B−H and Si−H bonds leads to the formation of hydride-bridged Pt−H−Zn complexes, which is not observed in the absence of Zn, pointing out the importance of metal-metal cooperation. Reactivity of PtMe2/M2+ with terminal acetylene, water and methanol is also studied, leading to facile protonation of one of the Me groups at the Pt center only when Zn is present. This study sheds light on various ways in which the presence of a 2+ metal cation significantly affects the reactivity of a common organoplatinum complex., source:https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202201639

Bond homolysis is one of the most fundamental bond cleavage mechanisms. Thus, understanding of bond homolysis influences the development of a wide range of chemistry. Photolytic bond homolysis and its reverse process have been observed directly using time-resolved spectroscopy. However, direct observation of reversible bond homolysis remains elusive. Here, we report the direct observation of reversible Co–Co bond homolysis using two-dimensional nuclear magnetic resonance exchange spectroscopy (2D EXSY NMR). The characterization of species involved in this homolysis is firmly supported by diffusion ordered NMR spectroscopy (DOSY NMR). The unambiguous characterization of the Co–Co bond homolysis process enabled us to study ligand steric and electronic factors that influence the strength of the Co–Co bond. Understanding of these factors will contribute to rational design of multimetallic complexes with desired physical properties or catalytic activity., source:https://pubs.rsc.org/en/content/articlelanding/2022/SC/D2SC03028D

Herein we report a versatile method for the preparation of triboluminescent polymer films by physical blending with common luminophores. This method does not require the presence of a crystalline phase or the use of materials known to be triboluminescent. Emission is generated in response to friction of the polymer surface via triboelectrification, either by rubbing directly or through an inert coating layer, even with low applied stress (<0.1 MPa). Our findings offer a convenient and practical method of preparation of triboluminescent, amorphous polymer films with easily tunable emission properties., source:https://pubs.acs.org/doi/10.1021/acsmacrolett.2c00348

We report a series of heterobimetallic Pt/Zn and Pt/Ca complexes to study the effect of proximity of a dicationic base metal on the organometallic Pt species. Varying degrees of Pt⋅⋅⋅Zn and Zn interaction with the bridging Me group are achieved, showcasing snapshots of a hypothetical process of retrotransmetalation from Pt to Zn. In contrast, only weak interactions were observed for Ca with a Pt-bound Me group. Activation of H2, B−H and Si−H bonds leads to the formation of hydride-bridged Pt−H−Zn complexes, which is not observed in the absence of Zn, pointing out the importance of metal-metal cooperation. Reactivity of PtMe2/M2+ with terminal acetylene, water and methanol is also studied, leading to facile protonation of one of the Me groups at the Pt center only when Zn is present. This study sheds light on various ways in which the presence of a 2+ metal cation significantly affects the reactivity of a common organoplatinum complex., source:https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202201639

Bond homolysis is one of the most fundamental bond cleavage mechanisms. Thus, understanding of bond homolysis influences the development of a wide range of chemistry. Photolytic bond homolysis and its reverse process have been observed directly using time-resolved spectroscopy. However, direct observation of reversible bond homolysis remains elusive. Here, we report the direct observation of reversible Co–Co bond homolysis using two-dimensional nuclear magnetic resonance exchange spectroscopy (2D EXSY NMR). The characterization of species involved in this homolysis is firmly supported by diffusion ordered NMR spectroscopy (DOSY NMR). The unambiguous characterization of the Co–Co bond homolysis process enabled us to study ligand steric and electronic factors that influence the strength of the Co–Co bond. Understanding of these factors will contribute to rational design of multimetallic complexes with desired physical properties or catalytic activity., source:https://pubs.rsc.org/en/content/articlelanding/2022/SC/D2SC03028D

Herein we report a versatile method for the preparation of triboluminescent polymer films by physical blending with common luminophores. This method does not require the presence of a crystalline phase or the use of materials known to be triboluminescent. Emission is generated in response to friction of the polymer surface via triboelectrification, either by rubbing directly or through an inert coating layer, even with low applied stress (<0.1 MPa). Our findings offer a convenient and practical method of preparation of triboluminescent, amorphous polymer films with easily tunable emission properties., source:https://pubs.acs.org/doi/10.1021/acsmacrolett.2c00348

Hydrogenation of substituted styrenes and unactivated aliphatic alkenes by molecular hydrogen has been achieved using a Mn catalyst with a non‐pincer, picolylphosphine ligand. This is the second reported example of alkene hydrogenation catalyzed by a Mn complex. Mechanistic studies showed that a Mn hydride formed by H2 activation in the presence of a base is the catalytically active species. Based on experimental and DFT studies, H2 splitting is proposed to occur via a metal‐ligand cooperative pathway involving deprotonation of the CH2 arm of the ligand, leading to pyridine dearomatization., source:https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/cctc.202001158

[Co(L)(CO)3]2 (L = CO or PR3) catalyzed hydroformylation of olefins is among the most successful homogeneous organometallic catalysis. The bimetallic [Co(L)(CO)3]2 complex exists in equilibrium with its mononuclear 17-electron [Co(L)(CO)3] metalloradical. However, isolation of the mononuclear metalloradical is unknown, and hence the role of this species in the catalytic cycle is difficult to study. Herein, we report the isolation of [Co(L)(CO)3] using ring-expanded N-heterocyclic carbene (reNHC) ligands. Isolation of this complex enabled us to examine feasibility of putative termolecular H2 activation by the [Co(L)(CO)3] metalloradicals. The kinetic experiments revealed that [Co(reNHC)(CO)3] does not activate H2 via a previously proposed termolecular mechanism but via a bimolecular mechanism. The result obtained here will contribute to design a cobalt carbonyl complex that activates H2 under mild conditions and to develop a more energy efficient oxo process based on economical cobalt catalysts., source:https://pubs.acs.org/doi/10.1021/acs.organomet.0c00765

The presence of Pd···Cu and Pd···Pd interactions as well as order of metal atoms in a chain held by a modular polynucleating ligand is controlled by coordinating ability of anions, leading to selective formation of bi- and tetranuclear Pd/Cu and Pd4 chains. Metal-metal cooperative reactivity in these complexes was tested in Ar–O bond formation and alkyne activation., source:https://pubs.rsc.org/en/content/articlelanding/2021/cc/d1cc04212b

Manganese complexes have been considered as a cheap and readily available alternative to commonly used precious metal catalysts in C–C bond coupling reactions. Although high-valent Mn aryl intermediates have been proposed in such reactions, a mechanistic understanding of possible organometallic intermediates in Mn-mediated C–C coupling is still lacking due to their high reactivity. We report the synthesis of stable, isolable Mn(III) aryl complexes obtained by oxidative addition of aryl bromide or aryl chloride. These complexes react with a range of organometallic alkylating or arylating reagents (alkyl and aryl Grignard reagents, MeLi, ZnMe2) to undergo C(sp2)–C(sp3) or C(sp2)–C(sp2) bond coupling, and a preliminary catalytic system could be demonstrated. The reagent scope and yield of the C(sp2)–C(sp3) coupled product can further be increased by addition of TEMPO as an oxidant, generating alkyl radicals., source:https://pubs.acs.org/doi/10.1021/acs.organomet.1c00047

We describe a series of air-stable NiIII complexes supported by a simple, robust naphthyridine-based ligand. Access to the high-valent oxidation state is enabled by the CF3 ligands on the nickel, while the naphthyridine exhibits either a monodentate or bidentate coordination mode that depends on the oxidation state and sterics, and enables facile aerobic oxidation of NiII to NiIII. These NiIII complexes act as efficient catalysts for photoinduced C(sp2)−H bond trifluoromethylation reactions of (hetero)arenes using versatile synthetic protocols. This blue LED light-mediated catalytic protocol proceeds via a radical pathway and demonstrates potential in the late-stage functionalization of drug analogs., source:https://onlinelibrary.wiley.com/doi/10.1002/anie.202109953

We report the synthesis and reactivity of RuII complexes with a new naphthyridinone-substituted phosphine ligand, 7-(diisopropylphosphinomethyl)-1,8-naphthyridin-2(1H)-one (L-H), which contains two reactive sites that can potentially be deprotonated by a strong base: an NH proton of naphthyridinone and a methylene arm attached to the phosphine. In the absence of a base, the stable bis-ligated complex Ru(L-H)2Cl2 (1) containing two NH groups in the secondary coordination sphere is formed. Upon further reaction with a base, a doubly deprotonated, dimeric complex is obtained, [Ru2(L*-H)2(L)2] (2), in which two of the four ligands undergo deprotonation at the NH (L), while the other two ligands are deprotonated at the methylene groups (L*-H) as confirmed by an X-ray diffraction study; intramolecular hydrogen bonding is present between the NH group of one ligand and an O-atom of another ligand in the dimeric structure, which stabilizes the observed geometry of the complex. Complex 2 reacts with protic solvents such as water or methanol generating aqua Ru(L)2(OH2)2 (3) or methanol complexes Ru(L)2(MeOH)2 (4), respectively, both exhibiting intramolecular H-bonded patterns with surrounding ligands at least in the solid state. These complexes react with benzyl alcohols to give aldehydes via base-free acceptorless dehydrogenation., source:https://pubs.rsc.org/en/content/articlelanding/2020/dt/d0dt02505d

Triboluminescent compounds that generate emission of light in response to mechanical stimulus are promising targets in the development of “smart materials” and damage sensors. Among triboluminescent metal complexes, rare-earth europium and terbium complexes are most widely used, while there is no systematic data on more readily available and inexpensive Cu complexes. We report a new family of photoluminescent Cu–NHC complexes that show bright triboluminescence (TL) in the crystal state visible in ambient indoor light under air. Moreover, when these complexes are blended into amorphous polymer films even at small concentrations, TL is easily observed. Observation of TL in polymer films overcomes the limitation of using crystals and opens up possibilities for the development of mechanoresponsive coatings and materials based on inexpensive metals such as Cu. Our results may also have implications for the understanding of the TL effect's origin in polymer films., source:https://pubs.rsc.org/en/content/articlelanding/2020/sc/d0sc04442c#!divAbstract

Cooperation between two different metals plays a crucial role in many synergistic catalytic reactions, such as the Sonogashira C-C cross-coupling reaction, where an interaction between the Pd and Cu centers is proposed in the transmetalation step. Although several heterobimetallic Pd/Cu complexes were proposed as structural models of the active species in Sonogashira coupling, the detailed understanding of the metal-metal cooperation in transmetalation is still lacking in current systems. In this work, we report a stepwise and systematic approach to building heteromultimetallic Pd/Cu assemblies as a tool to study metal-metal cooperativity. We obtained fully characterized Pd/Cu multimetallic assemblies that show reactivity in alkyne activation, formation of catalytically relevant aryl/acetylide species, and C-C elimination, serving as functional models for Sonogashira reaction intermediates. The combined experimental and DFT studies highlight the importance of ligand-controlled coordination geometry, metal-metal distances and dynamics of the multimetallic assembly for transmetalation step., source:https://chemistry-europe.onlinelibrary.wiley.com/doi/full/10.1002/chem.202002013

ARKIVOC: vol. 2011, no. 10, (issn) 1551-7012, (dlps) 5550190.0012.a02, This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 License. Please contact mpub-help@umich.edu to use this work in a way not covered by the license.

ARKIVOC: vol. 2011, no. 10, (issn) 1551-7012, (dlps) 5550190.0012.a02, This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 License. Please contact mpub-help@umich.edu to use this work in a way not covered by the license.