Ruthenium Olefin Metathesis Catalysts Containing Six-Membered Sulfone and Sulfonamide Chelating Rings

Tzur E., Szadkowska A., Ben-Asuly A., Makal A., Goldberg I., Woźniak K., Grela K., Lemcoff N. .

A short overview on the structural design of the Hoveyda-Grubbs-type ruthenium initiators chelated through oxygen, nitrogen or sulfur atoms is presented. Our aim was to compare and contrast O-, N- and S-chelated ruthenium complexes to better understand the impact of electron-withdrawing and -donating substituents on the geometry and activity of the ruthenium complexes and to gain further insight into the trans-cis isomerisation process of the S-chelated complexes. To evaluate the different effects of chelating heteroatoms and to probe electronic effects on sulfur- and nitrogen-chelated latent catalysts, we synthesised a series of novel complexes. These catalysts were compared against two well-known oxygen-chelated initiators and a sulfoxide-chelated complex. The structures of the new complexes have been determined by single-crystal X-ray diffraction and analysed to search for correlations between the structural features and activity. The replacement of the oxygen-chelating atom by a sulfur or nitrogen atom resulted in catalysts that were inert at room temperature for typical ring-closing metathesis (RCM) and cross-metathesis reactions and showed catalytic activity only at higher temperatures. Furthermore, one nitrogen-chelated initiator demonstrated thermo-switchable behaviour in RCM reactions, similar to its sulfur-chelated counterparts.

Vieille-Petit L., Clavier H., Linden A., Blumentritt S., Nolan S.P., Dorta R.

A series of second-generation ruthenium-based olefin metathesis catalysts bearing N-naphthyl-substituted N-heterocyclic carbene (NHC) ligands have been prepared and fully characterized. By reaction with the appropriate NHC, these complexes are readily accessible in one synthesis step from the commercially available first-generation precursors [RuCl2(═CHPh)(PCy3)2] (Grubbs I, GI) or [RuCl2(═CH-o-iPrO-Ph)(PCy3)] (Hoveyda−Grubbs I, HGI) by simple exchange of one phosphine ligand with the free NHCs. Time-dependent conversions in the ring-closing metathesis (RCM) of standard substrates leading to di- as well as trisubstituted olefins have been measured for these catalysts. When benchmarked against the parent SIMes-containing the Grubbs II precatalyst (GII), most of these new NHC structures show enhanced reactivity in RCM. From these comparative studies, valuable information was gathered which shows that the alkyl substitution on the naphthyl side chains can enhance or lower the catalytic performance, depending on the bulk and the position of these alkyl groups. The behavior of the best performing precatalysts has been investigated in the RCM of a series of representative substrates, in enyne metathesis reactions as well as in cross-metathesis (CM).

Gawin R., Czarnecka P., Grela K.

The novel catalytic system, composed of a ruthenium alkylidene containing a surfactant fragment in the catalysts molecule, is reported. Ring closing metathesis and cross metathesis reactions proceed efficiently in neat water at room temperature, in air, without need of adding an external surfactant.

Szadkowska A., Gstrein X., Burtscher D., Jarzembska K., Woźniak K., Slugovc C., Grela K.

The synthesis and characterization of two ruthenium complexes bearing chelating carbene ligands is described. Carbene precursors, 2-(2-vinylphenyl)pyridine and 10-vinylbenzo[h]quinoline, are applied to prepare (SPY-5-31)-dichloro-(κ2(C,N)-N-2-(2-vinylbenzylidene)pyridine(1,3-bis(2,4,6-trimethylphenyl)4,5-dihydroimidazol-2-ylidene)ruthenium (VIII) and (SPY-5-31)-dichloro-(κ2(C,N)-2-(benzo[h]quinolin-10-yl)methylidene)(1,3-bis(2,4,6-trimethylphenyl)4,5-dihydroimidazol-2-ylidene)ruthenium (IX). Both catalysts/initiators are used to perform ring-closing metathesis (RCM) and ring-opening metathesis polymerizations (ROMP). RCM experiments reveal significant thermal stability of the catalysts under forcing reaction conditions such as boiling toluene for 48 h. Even challenging substrates such as diethylallyl(2-methylallyl)malonate are completely transformed with low catalyst loadings (0.1 mol % at 110 °C). The high thermal stability, i.e., latency, might be explained by a slow generation of the catalytically acti...

Clavier H., Caijo F., Borré E., Rix D., Boeda F., Nolan S.P., Mauduit M.

The synthesis and characterization of three novel trifluoromethylamido-containing “boomerang” precatalysts bearing various N-heterocyclic carbene (NHC) ligands are reported. Comparative kinetic and stability studies show the significant effect of the NHC on the catalyst reaction profile. An investigation of the reaction scope for diverse metathesis transformations has allowed us to establish the influence of the NHC on catalyst activity, especially as a function of substrate steric bulk. The excellent stability of one of the novel

Szadkowska A., Makal A., Woźniak K., Kadyrov R., Grela K.

New ruthenium olefin metathesis initiators bearing sulfoxide moieties are described. The complexes were synthesized by the reaction of indenylidene ruthenium complexes Ind-II and Ind-II′ with different (2-vinyl)phenyl sulfoxides. These compounds show no catalytic activity at room temperature, but exhibit increased activity at elevated temperature. Preliminary studies on the influence of electronic and steric factors on the catalytic activity are presented.

Clavier H., Urbina-Blanco C.A., Nolan S.P.

The synthesis and characterization of a novel indenylidene-containing ruthenium catalyst bearing the N-heterocyclic carbene (NHC) ligand 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene (SIPr) are reported. Comparative reactivity studies with other indenylidene complexes using various substrates show the importance of the sterically demanding SIPr ligand on catalyst reaction profile. The investigation of the reaction scope for ring-closing metathesis transformations establishes the influence of the NHC on catalyst activity especially as a function of substrate steric bulk. The novel catalyst was found very efficient at room temperature for nonsterically hindered substrates. Since the new catalyst was found to be soluble in a variety of solvents, a number of these were examined to gauge the importance of solvent effects.

Burtscher D., Grela K.

On and under water: Recent developments in aqueous olefin metathesis have followed two main strategies: 1) the use of water-insoluble commercially available ruthenium catalysts in aqueous mixtures and neat water, and 2) the design of special polar ruthenium catalysts that are active and stable in aqueous media. The general applicability of water as a solvent for olefin metathesis is shown.

Szadkowska A., Grela K.

Kost T., Sigalov M., Goldberg I., Ben-Asuly A., Lemcoff N.G.

A series of sulfur chelated dormant ruthenium olefin metathesis catalysts is presented. The catalysts prepared were shown to possess the uncommon cis-dichloro arrangement and were mostly inactive at room temperature. By systematically modifying the size of the substituent groups at the chelating sulfur atom, catalyst activity at different temperatures was significantly affected; more bulky substituents fomented activity at lower temperatures. The catalysts were also shown to be stable in solution and retained their catalytic activity even after being exposed to air for two weeks.

Gułajski Ł., Michrowska A., Narożnik J., Kaczmarska Z., Rupnicki L., Grela K.

A polar olefin metathesis catalyst that bears a quaternary ammonium group was prepared from commercially available reagents. The electron-withdrawing quaternary ammonium group not only activates the Ru catalyst electronically but at the same time makes the catalyst more hydrophilic. The catalyst can therefore be efficiently used both in traditional media, such as dichloromethane and toluene, as well as in technical-grade alcohols, alcohol-water mixtures and in neat water. Various metathesis reactions, including ring-closing, cross- and enyne metathesis, were conducted in these solvents in the presence of air. In addition, the Ru catalyst can act as an inisurf (initiator and surfactant) molecule, promoting metathesis under heterogeneous aqueous conditions.

Ben-Asuly A., Tzur E., Diesendruck C.E., Sigalov M., Goldberg I., Lemcoff N.G.

The synthesis and characterization of a cis-dichloro sulfur chelated olefin metathesis catalyst is presented. The catalyst was extremely stable at room temperature in solution under ambient conditions and was shown to exhibit a thermo-switchable behavior for ring-closing olefin metathesis of diethyl diallylmalonate, being active at 80 °C and inactive at room temperature.

Bieniek M., Michrowska A., Usanov D., Grela K.

The data reported in this paper demonstrate that great care must be taken when choosing an appropriate catalyst for a given metathesis reaction. First-generation catalysts were found to be useful in the metathesis of sterically unhindered substrates. Second-generation catalysts (under optimised conditions) showed good to excellent activities toward sterically hindered and electron-withdrawing group (EWG)-substituted alkenes that do not react using the first-generation complexes. A strong temperature effect was noted on all of the reactions tested. Interestingly, attempts to force a reaction by increasing the catalyst loading were much less effective. Therefore, when possible, it is suggested that metathesis transformations should be carried out with a second-generation catalyst at 70 degrees C in toluene. However, different second-generation catalysts proved to be optimal for different applications and no single catalyst outperformed all others in all cases. Nevertheless, some empirical rules can be deduced from the model experiments, providing preliminary hints for the selection of the optimal catalysts.

Michrowska A., Grela K.

Abstract Attempts were made to create a catalyst that approaches Gladysz's vision of an "ideal catalyst". Modifications of the Hoveyda-Grubbs catalyst were carried out with the aim to increase its activity and broaden the scope of its applicability to challenging metathesis reactions. This was done by introduction of an electron-withdrawing substituent on the isopropoxybenzylidene group in order to diminish the donor properties of the oxygen atom. The resulting stable and easily accessible nitro-substituted Hoveyda-Grubbs catalyst has found a number of successful applications in various research and industrial laboratories. Also, a new concept for noncovalent immobilization of a ruthenium olefin metathesis catalyst is presented. The 2-isopropoxybenzylidene ligand of Hoveyda-Grubbs carbene is further modified by an additional amino group, and immobilization is achieved by treatment with sulfonated polystyrene, forming the corresponding ammonium salt. In this novel strategy for the immobilization of ruthenium-based metathesis catalysts, the amino group plays a dual role, being first an active anchor for immobilization and secondly, after protonation, activating the catalysts by electron-donating to -withdrawing switch. The same concept has been used in the preparation of a quaternary ammonium catalyst for aqueous olefin metathesis.

Gawin R., Makal A., Woźniak K., Mauduit M., Grela K.

Antonova Alexandra S., Zubkov Fedor I.

Catalytic olefin metathesis using Hoveyda-Grubbs type ruthenium complexes is a powerful tool for creating complex molecules possessing a variety of practically useful properties. This method is also applied for obtaining modern polymer materials from low-demand petroleum products. Among all ruthenium complexes containing five- or six-membered chelate rings, the commercially available HG-II catalyst is the most common. In addition, other Hoveyda-Grubbs type complexes, which include a Het→Ru donor–acceptor bond in the chelate ring, often exhibit metathesis activity equal to or superior to that of HG-II. This review considers second-generation N-heterocyclic ruthenium carbene Hoveyda-Grubbs type complexes with donor–acceptor bonds such as O→Ru, S→Ru, Se→Ru, N→Ru, P→Ru and Hal→Ru in the chelate ring. Methods of preparation, analysis of stability and catalytic activity of such complexes are compared, and examples of the application of these organometallic ruthenium derivatives in the synthesis of practically relevant products are provided. The literature from 2010 to 2023 is summarized, making this review useful for a broad audience of chemists working in heterocyclic and organometallic chemistry, as well as practitioners involved in the production of catalysts and polymers.The bibliography includes 174 references.

Bone K.I., Puleo T.R., Bandar J.S.

Cheng-Sánchez I., Moya-Utrera F., Sarabia F.

Kinugawa T., Matsuo T.

For regulating olefin metathesis (OM) activities of Hoveyda–Grubbs second-generation complex (HG-II), the structural modification of the benzylidene ligand is a useful strategy. This paper reports the effect of a chalcogen...

Borodina T.N., Smirnov V.I., Serykh V.Y., Rozentsveig I.B.

At present, sulfonamides and their metal complexes have received a new impetus for development. Of particular interest is the study of molecular and crystal structures, which takes into account weak non-valent interactions. Despite the low energy of such interactions, in many cases, they act collectively, and the sum of their actions can play a significant role. As a result, the spectrum of medical and biological activity of new metal complexes is expanded. In this regard, the synthesis and study of the molecular and crystal structure of sulfonamides and their metal complexes is of undoubted relevance. In this work, we studied non-valent intra- and intermolecular interactions in ligands of sulfonamide-substituted imidazo[2,1-b]thiazoles and their previously unknown complexes with CuCl2. The performed analysis of the data obtained by X-ray diffraction analysis made it possible to establish the intramolecular π-stacking interaction in imidazothiazole ligands, which is retained in their complexes with CuCl2. Within the framework of QTAIM topological analysis of electron density and DORI analysis, stereoelectronic and topological structures were studied. In the complexes, tetral, chalcogen, and pnycogen new interligand non-valent interactions were established. The energies of all established types of non-valent interactions have been calculated, and their comparative evaluation has been made. X-ray data of new arylsulfonylamino-substituted derivatives of imidazo[2,1-b]thiazoles and their metal complexes with CuCl2 have been studied. To determine the theoretical prerequisites for the occurrence of π-stacking in the molecules under study, the QTAIM method was used in the framework of the DFT/B3LYP/6–311 + G(d) calculation using the GAUSSIAN 09 program. In addition, the DORI electron density region overlap indicator and the Multiwfn program were used to analyze non-valent interactions.

Grela K., Kajetanowicz A., Szadkowska A., Czaban‐Jóźwiak J.

This chapter describes olefin cross‐metathesis (CM) reactions catalyzed by ruthenium, molybdenum, and tungsten complexes and surveys the literature from 1993 through 2020. Cross‐metathesis has been applied to the synthesis of a wide range of functionalized alkenes, including natural and biologically active products. Due to its simplicity and inherit atom economy, CM has found applications in the preparation of fine chemicals and various building blocks, and in transformations of biomass. Tandem reactions involving CM as the key step are also reviewed. Examples discussed in this chapter serve to illustrate how the reactivity of alkene substrates in CM depends on the presence of functional groups and steric congestion in the proximity of the reacting double bonds. A discussion of the mechanism of olefin metathesis is also included.

Wei W., Jia G.

The coordination chemistry of ruthenium, osmium, technetium and rhenium with carbon-based ligands covering the literature from 2003 to 2018 is discussed. These metals form a vast number of coordination compounds with carbon-based ligands ranging from a single carbon atom (a carbido ligand) to polydentate hydrocarbon chains, and from monodentate organometallic ligands such as carbenes to multidentate ligands such as pincers and macrocycles. Particular focus of this review is given to syntheses, properties and applications of complexes with popular carbon-based ligands such as monodentate N-heterocyclic carbenes (NHCs), cyclometallated bidentate ligands, tridentate pincers and porphyrin-like macrocycles.

Gupta S., Su S., Zhang Y., Liu P., Wink D.J., Lee D.

Metallaaromatics constitute a unique class of aromatic compounds where one or more transition metal elements are incorporated into the aromatic system, the parent of which is metallabenzene. One of the main concerns about metallabenzenes generally deals with the structural characterization related to their relative aromaticity compared to the carbon archetype. Transition metal-containing metallabenzenes are also implicated in certain catalytic processes such as alkyne metathesis polymerization; however, these transition metal-based metallaaromatic compounds have not been developed as a catalyst. Herein, we describe an effective strategy to generate diverse arrays of ruthenabenzenes and demonstrated them as an aromatic equivalent of the Grubbs-type ruthenium alkylidene catalysts. These ruthenabenzenes can be prepared via an enyne metathesis and metallotropic [1,3]-shift cascade process to form alkyne-chelated ruthenium alkylidene intermediates followed by spontaneous cycloaromatization. The aromatic nature of these complexes was confirmed by spectroscopic and X-ray crystallographic data, and the mechanistic pathways for the cycloaromatization process were studied by DFT calculations. These ruthenabenzenes display robust catalytic activity for metathesis and other transformations, which illustrates that metallabenzenes are not only compounds of structural and theoretical interests but also are a novel platform for new catalyst development.

Gupta S., Sabbasani V.R., Su S., Wink D.J., Lee D.

A variety of heteroatom-chelated ruthenium alkylidenes have been developed as metathesis-active catalysts. Alkene-chelated ruthenium alkylidenes, however, have not been considered as a viable alter...

Alazet S., Preindl J., Simonet-Davin R., Nicolai S., Nanchen A., Meyer T., Waser J.

Azides are building blocks of increasing importance in synthetic chemistry, chemical biology, and materials science. Azidobenziodoxolone (ABX, Zhdankin reagent) is a valuable azide source, but its safety profile has not been thoroughly established. Herein, we report a safety study of ABX, which shows its hazardous nature. We introduce two derivatives, tBu-ABX and ABZ (azidobenziodazolone), with a better safety profile, and use them in established photoredox- and metal-mediated azidations, and in a new ring-expansion of silylated cyclobutanols to give azidated cyclopentanones.

Barthelemy A., Prieto A., Diter P., Hannedouche J., Toffano M., Anselmi E., Magnier E.

We report herein the preparation of ortho-vinylaryl S-trifluoromethylated sulfoximines through cross-coupling reactions. Two efficient palladium-catalyzed procedures (Stille and Suzuki) were developed, with use of ortho-iodo aryl sulfox-imines as substrates, to give various vinyl derivatives in good yields. The difference in reactivity of the fluorinated derivatives,

Sabbasani V.R., Gupta S., Young Yun S., Lee D.

Ruthenium alkylidene complexes are prepared via enyne ring-closing metathesis relying on the exo and endo gem-dialkyl substituent effect.

Omae I.

Cyclometalated six-membered ring products have been reported in applications as catalysts and OLEDs. The 2-benzylpyridine gold dichloride for the formation of tri-substituted oxazoles, the similar 2-benzylpyridine PEG-linked compound for the synthesis of propargylic amines, a biphenyl palladium compound for polycondensation using the Suzuki-Miyaura cross-coupling reaction, a naphthalene palladacycle for the ring-opening reaction of 7-oxabenzonorbornadiene with phenylacetylene, a sulfone oxygen donor ruthenium compound for the ring-closing metathesis of unhindered diene, and the non-symmetric NCN-Pd pincer compound for the Suzuki-Miyaura couplings of para -substituted bromobenzenes with phenylboronic acid have all been shown to be efficient catalysts. Quinoline iridium compounds show deep red phosphorescent emissions with short lifetimes, which is promising for the uses in OLED displays. Bis-pyridine, bis-carbazole tetradentate platinum compounds were proved to be successful for achieving deep blue emission onsets as low as 420 nm, with estimated lifetimes of greater than 500 h at 1000 cd/m 2 .

Liang T., Chen C.

A series of phosphine-sulfonate ligands bearing various side-arm substituents were designed and prepared. The corresponding Pd(II) complexes [κ2-(P,O)-2-(PPhAr)-1-benzenesulfonato]Pd(Me)(dmso) (Pd1, Ar = o-MeO-C6H4; Pd2, Ar = o-PhO-C6H4; Pd3, Ar = o-(2,6-Me2-C6H3)O-C6H4; Pd4, Ar = o-PhSO2-C6H4) and Ni(II) complexes [κ2-(P,O)-2-(PPhAr)-1-benzenesulfonato]NiPh(PPh3) (Ni1, Ar = o-MeO-C6H4; Ni2, Ar = o-PhO-C6H4; Ni3, Ar = o-(2,6-Me2-C6H3)O-C6H4; Ni4, Ar = o-PhSO2-C6H4) were prepared and applied in ethylene polymerization and ethylene–polar monomer copolymerization. Catalysts Pd2, Pd3, Ni2, and Ni3 are moderately active in ethylene polymerization (activity up to 8.7 × 105 g mol–1 h–1), generating polyethylene with high molecular weights (Mn up to 105100) and high melting temperatures (Tm up to 131.6 °C). The two palladium catalysts can also initiate efficient copolymerization of ethylene with methyl acrylate, allyl cyanide, and allyl acetate. Most importantly, high copolymer molecular weights (Mn between 21600...

Dayan S., Kayaci N., Kalaycioglu Ozpozan N., Dayan O.

[RuLCl(p-cymene)] (L = N-arylsulfonylphenylenediamine) complexes (2a–d) were synthesized from the reaction between [Ru(p-cymene)Cl2]2 and ligand. Additionally, SBA-15–[RuLCl(p-cymene)] derived catalysts (3a–d) were successfully immobilized onto mesoporous silica (SBA-15) by an easily accessible approach. The structural elucidations of 2a–d and 3a–d were carried out with various methods such as 1H NMR, 13C NMR and infrared spectroscopies, elemental analysis, thermogravimetric/differential thermal analysis, nitrogen adsorption–desorption and scanning electron microscopy/energy-dispersive X-ray analysis. The Ru(II) complexes and materials were found to be highly active and selective catalysts for the transfer hydrogenation (TH) reaction of aldehydes and ketones. The influence of various 1,2-phenylenediamines on the reactivity of the catalysts (complexes or materials) was studied and the catalysts (2d and 3d) with a 4,5-dichlorophenylenediamine substituent showed the best activity (the maximum turnover frequencies are 2916 and 2154 h−1 for TH of 4-fluoroacetophenone, and 6000 and 4956 h−1 for TH of 4-chlorobenzaldehyde).