Skip to main content
NCBI home page
Wiley Open Access Collection logoLink to Wiley Open Access Collection
. 2026 Mar 4;65(16):e6803845. doi: 10.1002/anie.6803845

A Convenient, Safe, and Atom‐Economical Route to a Large Portfolio of Grubbs‐Type Catalysts for Olefin Metathesis via Four‐Coordinate Ruthenium Alkylidynes

Mingxu Cui 1, Alois Fürstner 1,✉
PMCID: PMC13080428  PMID: 41778445

ABSTRACT

p‐Tolyl(trimethylsilyl)diazomethane is a readily accessible and easy‐to‐handle net carbyne donor reagent. It reacts with [(p‐cymene)RuCl2]2 in MeCN to give the phosphine‐free chloride‐bridged dinuclear complex [(MeCN)2RuCl2( = C(p‐tolyl)(SiMe3))]2 (2) carrying a silyl group on each of the carbene ligands. Treatment of 2 with either PCy3 or an N‐heterocyclic carbene (NHC) causes elimination of TMSCl with formation of the corresponding four‐coordinate ruthenium alkylidynes. The non‐bonding electron lone pair of significant dz2 character at their Ru center is prone to protonation; in this way, the alkylidyne unit is converted into a carbene ligand under very mild conditions. The sequence of alkylidyne formation/protonation opens a novel entry into all relevant “generations” of Grubbs and Grubbs‐Hoveyda type catalysts, which is distinguished by a superior ligand‐ and atom economy, a good safety profile, and high overall yields. Moreover, the method is inherently flexible and arguably suitable for parallel screening and reaction optimization purposes.

Keywords: atom economy, diazo derivatives, metathesis, ruthenium alkylidynes, ruthenium carbenes

It may seem counterintuitive to first target a ruthenium alkylidyne when Grubbs‐type ruthenium carbene complexes are the actual goal. In the end, however, this tactic pays valuable dividends in terms of practicality, atom economy, flexibility as well as safety: the new route provides ready access to a large assortment of catalysts for alkene metathesis via a universal precatalyst that is easy to make and handle.

graphic file with name ANIE-65-e6803845-g012.jpg

1. Introduction

In a recent Communication, we reported that p‐tolyl(trimethylsilyl)diazomethane (1) reacts with [(p‐cymene)RuCl2]2 in acetonitrile to give the chloride‐bridged dinuclear complex 2 with a silyl group on each of the carbene ligands (Scheme 1) [1, 2]. Subsequent exposure to the lithium salt 3 entailed rapid elimination of TMSCl with formation of the ruthenium alkylidyne 4 endowed with a PNP‐pincer ligand. The reactivity of this formally d4‐configured complex is dominated by the non‐bonding lone pair of significant dz2 character, which constitutes the largely metal‐centered HOMO. As a result, 4 engages polarized alkynes such as methyl 2‐butynoate in a stepwise rather than concerted [2+2] cycloaddition to give the metallacyclobutadiene 5; this transformation resembles an inorganic Michael‐type reaction triggered by attack of the lone pair onto the acceptor substrate, followed by collapse of the resulting dipolar intermediate A [1].

SCHEME 1.

SCHEME 1

Open in a new tab

Use of a silylated aryldiazo derivative as carbyne donor reagent (ref [1]) and prototype reactivity of formally d4 configured ruthenium alkylidynes.

Although such a stepwise process is a handicap for cycloreversion and prevents catalytic alkyne metathesis from occurring [1], we saw another opportunity for taking advantage of the peculiar chemical character of ruthenium alkylidynes of this type. Specifically, the high‐lying lone pair should render such complexes susceptible to protonation or regular oxidative addition to the H−Cl bond; the resulting hydride species B is expected to undergo facile 1,2‐H shift with formation of a carbene as the final product. Indeed, the alkylidyne complex 4 reacts instantly with ethereal HCl to furnish the corresponding carbene complex 7 in high yield, the constitution of which was confirmed by X‐ray diffraction analysis (the structure is contained in the Supporting Information) [3]. It had been known in the literature that ruthenium alkylidynes such as 9 can be protonated, but the reported example was no more than a “short circuit” of little preparative value, as starting material and product were identical (see the Insert in Scheme 1) [4, 5].

With a new and facile access route to ruthenium alkylidynes in place, however, the situation might change and reward could be drawn from the protonation bias. Provided that the reactivity manifested in the formation of 4 and 7 can be generalized and monodentate phosphines or NHC's be used instead of the PNP pincer ligand, venerable Grubbs‐type catalysts for olefin metathesis might come into reach [6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]. The envisaged sequence of alkylidyne formation/protonation should offer notable advantages, which become apparent when considering the genesis of the iconic Grubbs catalysts (Scheme 2). All of them derive from complex 10, which in turn is obtained by reacting hazardous phenyldiazomethane [21] with [(PPh3)3RuCl2] under cryogenic conditions [22]. Ligand exchange then affords the prototypical first‐generation Grubbs catalyst 11 [22, 23]; already at this stage, all three PPh3 ligands of [(PPh3)3RuCl2] have been wasted. Upon conversion of 11 into any of the later generation catalysts exemplified by 12 (R = 2,4,6‐trimethylphenyl) [24, 25, 26], 12 (R = CHMePh) [27], 13 [28, 29], 14 [30, 31], 15 [32, 33], 16 [34], or 17 [35], the “phosphine economy” gets even worse. It is somewhat paradox and arguably disturbing that five equivalents of valuable phosphines must be sacrificed in order to make entirely phosphine‐free catalysts such as 15 or 16. Moreover, a phosphine scavenger such as stoichiometric CuCl is needed in certain cases. It should be remembered that meticulous purification is imperative since any residual phosphine in a sample of a Grubbs‐type catalyst entails greatly diminished catalytic activity as it will compete with the substrate for the binding to the metal center [7].

SCHEME 2.

SCHEME 2

Open in a new tab

The genesis of the different generations of classical Grubbs‐type catalysts exhibits poor “ligand economy”.

2. Results and Discussion

Provided that our new phosphine‐free silylated carbene dimer 2 (or analogs thereof) can be used as an alternative entry point, these problems might get solved [36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47]. The fact that we had already managed in our previous study to prepare multigram quantities of complex 2 made us confident that scalability is a realistic outlook [1]. Actually, 2 is very easy to make: it precipitates from the mixture when [(p‐cymene)RuCl2]2 is reacted with the silylated diazo derivative 1 in MeCN at ambient temperature and can therefore be isolated by simple filtration; moreover, this complex is bench‐stable when kept dry and can be weighed and handled in air. Likewise, the required carbyne donor 1 is available in only three high‐yielding operations on multi‐gram scale starting from 4‐methylbenzoic acid chloride (for details, see the Supporting Information) [48, 49]. Arguably most important, however, is the fact that this particular diazo derivative and its analogues are safe to use due to the massive stabilizing effect of the silyl group. While we found the crude product 1 (Ar = p‐tolyl) pure enough for direct use, it can be distilled in vacuo if one desires so (58°C–61°C, 0.2 mm) [49]; its sibling (Ar = Ph) is reported to survive even at temperatures of up to 135°C (0.3 mm) [2, 50]. This remarkable thermal stability distinguishes 1 from phenyldiazomethane used en route to the classical Grubbs carbenes, which has to be handled with the greatest care and must be reacted at cryogenic conditions (Scheme 2) [22, 51]. Moreover, and again in stark contrast to phenyldiazomethane, compound 1 can be stored for months in a refrigerator without notable decomposition.

Just like in the case of the pincer ligand leading to 4 [1], addition of PCy3 to a suspension of 2 in toluene causes elimination of TMSCl to give the corresponding four‐coordinate ruthenium alkylidyne complex 9 in good yield (Scheme 3). This compound is known in the literature, but had been prepared by deprotonation of the Grubbs catalyst 8 with a particular germylene as the optimal base (see Insert in Scheme 1) [4, 5]. The spectroscopic data of our sample were fully matching, with the deshielded signal of the alkylidyne C‐atom being most characteristic (δC = 237.8 ppm, t, J C,P = 18.4 Hz). However, crystals suitable for X‐ray diffraction analysis had not been attained in the past. Figure 1 shows the structure of 9 in the solid state [3]. As expected, the two phosphines are trans to each other within the square‐planar coordination sphere of the Ru‐center. The Ru(1)−C(1) bond length of 1.7103(16) Å compares well to that of the few other known (mostly higher valent) ruthenium alkylidynes [1, 5, 52, 53, 54, 55, 56], and the Ru(1)−Cl(1) bond (2.4357(4) Å) is slightly elongated as one might expect due to the strong trans‐effect of the alkylidyne ligand. In close analogy to complex 26 discussed below, the HOMO of the complex is a high‐lying metal‐centered lone pair of significant dz2 character (for details, see the Supporting Information).

SCHEME 3.

SCHEME 3

Open in a new tab

New route to “first generation” Grubbs‐ and Grubbs/Hoveyda‐type catalysts and an application to “instant” metathesis reactions; [a] with 2.5 mol% of 2; [b] with 5 mol% of 2.

FIGURE 1.

FIGURE 1

Open in a new tab

Structure of the four‐coordinate ruthenium alkylidyne 9 in the solid state (thermal ellipsoids at the 40 % probability level); hydrogen atoms and solute toluene in the unit cell omitted for clarity (the full structure is contained in the Supporting Information). Selected bond lengths (Å) and angles (°): Ru1‐Cl1 2.4357(4), Ru1‐P1 2.3845(4), Ru1‐P2 2.3878(4), Ru1‐C1 1.7103(16), C1‐C2 1.445(2); C1‐Ru1‐Cl1 178.12(5); Ru1‐C1‐C2 178.20(13).

Addition of ethereal HCl to a solution of 9 in toluene resulted in the virtually quantitative formation of the “first generation” Grubbs‐type catalyst 8. Its preparation can be further streamlined in that the ruthenium alkylidyne 9 does not even have to be isolated. Rather, it suffices to stir a mixture of 2 and PCy3 in toluene at 50°C for 30 min and then add, for example, 2,6‐di‐tert‐butylpyridinium chloride (18) as a convenient, crystalline source of HCl to the mixture [57]. Under these conditions, complex 8 was cleanly formed and isolated in 85% yield by filtration, evaporation of the solvent, and washing of the crude product with MeOH. An extension to the formation of the “first generation” Grubbs‐Hoveyda type catalyst 14a or the corresponding nitro‐substituted variant 14b is equally straightforward: [30, 58] all it takes is to stir a mixture of 2, PCy3(1 equiv.), the corresponding styrene 17a,b and HCl in toluene to obtain these popular catalysts in good yield each. It is important to note that no phosphine is wasted in either case, which is in marked contrast to the literature routes.

Moreover, 8 can be generated in the presence of an olefinic substrate. As shown by the examples compiled in Scheme 3 (bottom), the yields obtained by this “instant metathesis” procedure are perfectly comparable to those reported in the literature for the exact same products 20–24 [59, 60, 61, 62, 63, 64] using authentic first‐generation Grubbs catalyst.

Next, it was shown that the reaction of 2 with various N‐heterocyclic carbenes (NHC) instead of PCy3 also entails the formation of the corresponding ruthenium alkylidynes [65], as evident from the characteristic signals of their alkylidyne C‐atoms (25: δC = 229.3 ppm; 26: δC = 222.9 ppm; 27: 229.3 ppm) (Scheme 4). In case of 26, the assignment was confirmed by X‐ray diffraction analysis, which proved the regular square planar coordination geometry of this complex (Figure 2) [3]. At the same time, however, the very congested environment about the ruthenium center becomes apparent, in that the planes of the two imidazol‐2‐ylidene rings are notably tilted against each other, and the alkylidyne “intercalated” in between them is also twisted in order to find enough space. DFT studies at the B3LYP‐D4/def2‐tzvp CPCM(toluene) level of theory [66, 67, 68, 69, 70, 71] using the ORCA 6.0 program package [72] confirmed that 26 has a high‐lying, largely metal‐centered lone pair of significant dz2 character representing the HOMO of the complex (Figure 3). As expected, the strongly σ‐donating NHC ligands evidently render it highly electron‐rich and hence protonation‐prone.

SCHEME 4.

SCHEME 4

Open in a new tab

Ruthenium alkylidyne complexes endowed with two NHC ligands.

FIGURE 2.

FIGURE 2

Open in a new tab

Structure of complex 26 in the solid state (thermal ellipsoids at the 40 % probability level) shown in front‐ and top view to illustrate the congested coordination sphere; H‐atoms and solute n‐pentane in the unit cell omitted for clarity. Selected bond lengths (Å) and angles (°): Ru1‐C1 1.7178(13), Ru1‐Cl1 2.4199(3), C1‐C2 1.4456(19), Ru1‐C9 2.1076(13), Ru1‐C36 2.1106(13), Cl1‐Ru1‐C1 178.67(5), C9‐Ru1‐C36 172.76(5), Ru1‐C1‐C2 178.32(11); plane C9‐N1‐N2 to plane C36‐N3‐N4 twist angle: 40.18(6).

FIGURE 3.

FIGURE 3

Open in a new tab

LUMO (top) and HOMO (bottom) of the four‐coordinate ruthenium alkylidyne complex 26 endowed with two NHC ligands; the full frontier MO diagram is contained in the Supporting Information.

In line with this notion, addition of one equivalent of HCl selectively hits this lone pair; the transient hydride species instantly converts into the corresponding “latent” metathesis catalysts, as demonstrated by the preparation of 28 and 35 (Scheme 5) [35]. Addition of a second equivalent of HCl then protonates one of the NHC ligands off, causing the precipitation of the corresponding imidazolium salt 30, which can be collected by filtration and re‐converted into the NHC upon treatment with an appropriate base. The formally four‐coordinate ruthenium carbene concomitantly formed (if one disregards the weakly coordinating solvent) is dimerization‐prone; in any case, the DOSY data speak for a dimer in solution (see the Supporting Information) and the X‐ray diffraction analysis confirmed the presence of the chloride‐bridged dinuclear species [29]2 in the solid state (Figure 4) 3. Somewhat surprisingly, this complex differs from related dimers known in the literature [73, 74, 75] in that the two 4‐methylbenzylidene units are oriented cis rather than trans to each other. This peculiar spatial arrangement may explain why [29]2 is primed for decomposition by bimolecular coupling of the carbene units in solution [76, 77, 78]. In the solid state, however, the complex can be kept even at ambient temperature for ≥ 1 month without significant decomposition; it may therefore serve as a valuable fast‐initiating catalyst [75].

SCHEME 5.

SCHEME 5

Open in a new tab

A portfolio of Grubbs‐type catalysts, all derived from ruthenium alkylidynes endowed with two NHC ligands: (a) 2,6‐lutidinium chloride, toluene; (b) HCl in 1,4‐dioxane (4 M), toluene; (c) HCl in Et2O (0.5 M), PCy3, toluene; (d) HCl in Et2O (0.5 M), DMSO, toluene; (e) IPr, toluene, 50°C, then pyridinium hydrochloride; (f) IPr, toluene, 50°C, then HCl in 1,4‐dioxane (4 M), 3‐bromopyridine; (g) HCl in Et2O (0.5 M), 1‐isopropoxy‐2‐vinylbenzene (17a), toluene, 50°C; h) IPr, toluene, 50°C, then 1‐isopropoxy‐4‐nitro‐2‐vinylbenzene, HCl in 1,4‐dioxane (4 M); IPr = 1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene.

FIGURE 4.

FIGURE 4

Open in a new tab

Structure of complex [29]2 in the solid state (thermal ellipsoids at the 40% probability level); H‐atoms and solute CH2Cl2 and n‐hexane in the unit cell omitted for clarity. Selected bond lengths (Å) and angles (°): Ru1‐C28 1.829(3), Ru1‐C1 2.004(3), Ru2‐C68 1.833(3), Ru2‐C41 2.004(3), C28‐C68 6.17(7); Ru1‐C28‐C29 129.8(2), Ru2‐C68‐C69 130.5(2); C28‐Ru1‐Ru2‐C68 16.54(14).

When PCy3 is present in the reaction mixture while forming [29]2 in this way, the “second generation” Grubbs catalyst 31 is directly obtained in good yield [26]. Once again, 31 can be generated in situ in the presence of an olefin to be metathesized, thus extending the scope of the “instant procedure” to reactions requiring such “second generation” catalysts. The RCM reaction leading to the trisubstituted butenolide 38 shown in Scheme 5 is representative (for an additional example, see the Supporting Information) [79].

The ability to form heteroleptic complexes is by no means limited to the use of phosphines. Rather, dimethylsulfoxide can also be introduced to give complex 32, which is cis‐configured and has precedent in the olefin metathesis literature [80]. Likewise, “third generation” Grubbs type complexes such as 33a,b are easily reached by performing the protonation of 26 with the appropriate pyridinium hydrochloride as source of HCl and the donor ligand alike. Complexes of this type are able to metathesize acrylonitrile [34]; as particularly fast‐initiating catalysts [81], they are also enabling tools for material science [82, 83]. Protonation of 26 in the presence of stoichiometric 2‐isopropoxystyrene triggers a cross metathesis reaction to furnish the corresponding “second generation” Grubbs‐Hoveyda type catalyst 34a in high yield on gram scale; of course, the analogous nitro‐Grela catalyst 34b is equally within reach as are the analogous complexes 15 and 36 bearing saturated NHC ligands. In no case is any phosphine wasted, the use of phosphine scavengers is unnecessary, and all catalyst samples prepared by this route are hence free of residual PR3 that might interfere with their activity. Moreover, the ability to quickly and cleanly generate different ruthenium carbene complexes starting directly from 2 in combination with the “instant metathesis” procedure that allows their catalytic performance to be assessed in situ should lend itself to parallel screening and reaction optimization purposes [84].

Finally, it is worth noting that exchange of the labile acetonitrile ligands of 2 for other ligands is also possible without concomitant formation of an alkylidyne unit by elimination of TMSCl. This provides opportunities to access entirely new types of ruthenium carbene complexes. Thus, addition of excess pyridine to a solution of 2 in MeCN left the silylated carbene unit intact. In contrast to the dinuclear acetonitrile adduct 2, the resulting adduct 39 is well soluble in common organic solvents such as toluene and dichloromethane. In solution, it consists of a mixture of two diastereomers (trans:cis ≈ 95:5, NOE); the exceptionally deshielded carbene signal of the major isomer at δC = 403 ppm is noteworthy. Recrystallization of the crude product from CH2Cl2/n‐hexane did not cause TMSCl‐elimination either but gave single crystals suitable for X ‐ray diffraction of the cis‐isomer (see the Supporting Information) [85] as well as the chloride‐bridged dimer 40 (Figure 5) [3]. Interestingly, complex 39 is capable of entertaining a high yielding stoichiometric metathesis reaction with styrene to give the benzylidene complex 41, which exists as a cis/trans‐mixture in CD2Cl2 solution (Scheme 6); single crystals of the trans‐isomer suitable for X‐ray diffraction analysis were obtained (Figure 6) [3]. Attempts at using complexes 39 or 40 as catalysts were so far largely met with failure as the labile and unencumbered pyridine ligands are apparently incapable of stabilizing the reactive carbene unit (or the derived methylidene species) to the necessary extent [86].

FIGURE 5.

FIGURE 5

Open in a new tab

Structure of complex 40 in the solid state (thermal ellipsoids at the 40% probability level); H‐atoms omitted for clarity. Selected bond lengths (Å): Ru1‐C1 1.8678(17), C1‐Si1A 1.940(10), Ru1‐Cl2A 2.6530(4).

SCHEME 6.

SCHEME 6

Open in a new tab

Ligand exchange with formation of the Ru benzylidene complex 41 exclusively ligated to pyridine.

FIGURE 6.

FIGURE 6

Open in a new tab

Structure of complex trans‐41 in the solid state; H‐atoms omitted for clarity. Selected bond lengths (Å): Ru1‐C1 1.868(2), Ru1‐N2 2.3268(19), Ru1‐N1 2.0891(19), Ru1‐N3 2.0931(19).

3. Conclusions

In summary, we outline a novel, practical, flexible and high‐yielding entry into a large portfolio of Grubbs‐type ruthenium carbene complexes for use in olefin metathesis. From the conceptual viewpoint, the new route is distinguished by the fact that it passes through ruthenium alkylidynes in the first place and takes advantage of their propensity to undergo protonation, which is rooted in the high‐lying lone pair at the formally d4‐configured ruthenium center. In practical terms, the new procedure excels with regard to its flexibility as well as an unmatched “ligand economy”; this virtue stands in marked contrast to the classical literature routes, where up to five equivalents of valuable phosphines have to be sacrificed for the preparation of what are ultimately phosphine‐free catalysts. Since the required ruthenium alkylidynes themselves are readily accessible with the aid of silylated aryldiazomethane derivatives as stable, safe and readily accessible carbyne donor reagents, the new method is deemed to mark an important advance in the field. Further studies in this laboratory are underway to fully exploit the opportunities that it provides.

Conflicts of Interest

Patent applied for.

Supporting information

Supporting File 1: anie71722‐sup‐0001‐SuppMat.pdf.

ANIE-65-e6803845-s001.pdf (5MB, pdf)

Acknowledgments

Generous financial support by the Max‐Planck‐Society is acknowledged with gratitude. We thank Mr. K. Miyamoto for experimental support, Dr. M. Leutzsch for help with the characterization of some of the complexes by NMR spectroscopy, J. Rust, Dr. N. Nöthling, Dr. R. Goddard and Prof. C. W. Lehmann for solving the X‐ray structures, and all analytical departments of the MPI for excellent service.

Open access funding enabled and organized by Projekt DEAL.

Data Availability Statement

The data that supports the findings of this study are available in the supplementary material of this article.

References

  • 1. Cui M., Leutzsch M., Auer A. A., and Fürstner A., “Square‐Planar Ruthenium Alkylidyne Complexes Undergo Stepwise Rather than Concerted [2 + 2] Cycloadditions With Alkynes,” Angewandte Chemie International Edition 65 (2026): e19905. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 2.The p‐tolyl residue was solely chosen to facilitate product identification by NMR. Phenyl(trimethylsilyl)diazomethane can be prepared analogously and reacts similarly well, thus giving access to the analogous ruthenium complexes bearing an unsubstituted benzylidene or benzylidyne unit. Details will be reported in a future full paper.
  • 3.Deposition numbers CCDC 2431917 (7), 2431916 (9), 2525554 (26), 2515555 ([29]2 ), 2515553 (39), 2515552 (40), 2515551 (41), 2431911 (acylpalladiuim complex S2) contain the supplementary crystallographic data for this paper. These data are provided free of charge by the joint Cambridge Crystallographic Data Centre and Fachinformationszentrum Karlsruhe Access Structure service. Relevant crystallographic data are also contained in the Supporting Information.
  • 4. Caskey S. R., Stewart M. H., Ahn Y. J., Johnson M. J. A., Rowsell J. L. C., and Kampf J. W., “Synthesis, Structure, and Reactivity of Four‐, Five‐, and Six‐Coordinate Ruthenium Carbyne Complexes,” Organometallics 26 (2007): 1912–1923, 10.1021/om061192v. [DOI] [Google Scholar]
  • 5. Caskey S. R., Stewart M. H., Ahn Y. J., Johnson M. J. A., and Kampf J. W., “Dehydrohalogenation by a Germylene:  Conversion of Carbene Ligands Into Carbynes at Ruthenium,” Organometallics 24 (2005): 6074–6076, 10.1021/om0508482. [DOI] [Google Scholar]
  • 6. Grubbs R. H., “Olefin‐Metathesis Catalysts for the Preparation of Molecules and Materials (Nobel Lecture),” Angewandte Chemie International Edition 45 (2006): 3760–3765, 10.1002/anie.200600680. [DOI] [PubMed] [Google Scholar]
  • 7. Grubbs R. H. and O'Leary D. J., Handbook of Metathesis, 2nd ed. (Wiley‐VCH, 2015), 10.1002/9783527674107. [DOI] [Google Scholar]
  • 8. Fürstner A., “Olefin Metathesis and Beyond,” Angewandte Chemie International Edition 39 (2000): 3012–3043, 10.1002/1521-3773(20000901)39:17<3012::AID-ANIE3012>3.0.CO;2-G. [DOI] [PubMed] [Google Scholar]
  • 9. Connon S. J. and Blechert S., “Recent Developments in Olefin Cross‐Metathesis,” Angewandte Chemie International Edition 42 (2003): 1900–1923, 10.1002/anie.200200556. [DOI] [PubMed] [Google Scholar]
  • 10. Hoveyda A. H., Gillingham D. G., Van Veldhuizen J. J., et al., “Ru Complexes Bearing Bidentate Carbenes: From Innocent Curiosity to Uniquely Effective Catalysts for Olefin Metathesis,” Organic & Biomolecular Chemistry 2 (2004): 8, 10.1039/b311496c. [DOI] [PubMed] [Google Scholar]
  • 11. Hoveyda A. H. and Zhugralin A. R., “The Remarkable Metal‐Catalysed Olefin Metathesis Reaction,” Nature 450 (2007): 243–251, 10.1038/nature06351. [DOI] [PubMed] [Google Scholar]
  • 12. Deshmukh P. H. and Blechert S., “Alkene Metathesis: The Search for Better Catalysts,” Dalton Transactions 24 (2007): 2479, 10.1039/b703164p. [DOI] [PubMed] [Google Scholar]
  • 13. Buchmeiser M. R., “Polymer‐Supported Well‐Defined Metathesis Catalysts,” Chemical Reviews 109 (2009): 303–321, 10.1021/cr800207n. [DOI] [PubMed] [Google Scholar]
  • 14. Samojłowicz C., Bieniek M., and Grela K., “Ruthenium‐Based Olefin Metathesis Catalysts Bearing N ‐Heterocyclic Carbene Ligands,” Chemical Reviews 109 (2009): 3708–3742, 10.1021/cr800524f. [DOI] [PubMed] [Google Scholar]
  • 15. Vougioukalakis G. C. and Grubbs R. H., “Ruthenium‐Based Heterocyclic Carbene‐Coordinated Olefin Metathesis Catalysts,” Chemical Reviews 110 (2010): 1746–1787, 10.1021/cr9002424. [DOI] [PubMed] [Google Scholar]
  • 16. Fürstner A., “Metathesis in Total Synthesis,” Chemical Communications 47 (2011): 6505, 10.1039/c1cc10464k. [DOI] [PubMed] [Google Scholar]
  • 17. Fürstner A., “Teaching Metathesis “Simple” Stereochemistry,” Science 341 (2013): 1229713, 10.1126/science.1229713. [DOI] [PubMed] [Google Scholar]
  • 18. Grela K., ed., Olefin Metathesis: Theory and Practice (Wiley, 2014), 10.1002/9781118711613. [DOI] [Google Scholar]
  • 19. Higman C. S., Lummiss J. A. M., and Fogg D. E., “Olefin Metathesis at the Dawn of Implementation in Pharmaceutical and Specialty‐Chemicals Manufacturing,” Angewandte Chemie International Edition 55 (2016): 3552–3565, 10.1002/anie.201506846. [DOI] [PubMed] [Google Scholar]
  • 20. Ogba O. M., Warner N. C., O'Leary D. J., and Grubbs R. H., “Recent Advances in Ruthenium‐Based Olefin Metathesis,” Chemical Society Reviews 47 (2018): 4510–4544, 10.1039/C8CS00027A. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 21. Sammakia T., Encyclopedia of Reagents for Organic Synthesis (Wiley, 2001). [Google Scholar]
  • 22. Schwab P., Grubbs R. H., and Ziller J. W., “Synthesis and Applications of RuCl2 (CHR′)(PR3)2:  The Influence of the Alkylidene Moiety on Metathesis Activity,” Journal of the American Chemical Society 118 (1996): 100–110, 10.1021/ja952676d. [DOI] [Google Scholar]
  • 23.See also: Nguyen S. T., Grubbs R. H., and Ziller J. W., “Syntheses and Activities of New Single‐Component, Ruthenium‐Based Olefin Metathesis Catalysts,” Journal of the American Chemical Society 115 (1993): 9858–9859, 10.1021/ja00074a086. [DOI] [Google Scholar]
  • 24. Scholl M., Trnka T. M., Morgan J. P., and Grubbs R. H., “Increased Ring Closing Metathesis Activity of Ruthenium‐Based Olefin Metathesis Catalysts Coordinated With Imidazolin‐2‐ylidene Ligands,” Tetrahedron Letters 40 (1999): 2247–2250, 10.1016/S0040-4039(99)00217-8. [DOI] [Google Scholar]
  • 25. Huang J., Stevens E. D., Nolan S. P., and Petersen J. L., “Olefin Metathesis‐Active Ruthenium Complexes Bearing a Nucleophilic Carbene Ligand,” Journal of the American Chemical Society 121 (1999): 2674–2678, 10.1021/ja9831352. [DOI] [Google Scholar]
  • 26. Fürstner A., Ackermann L., Gabor B., et al., “Comparative Investigation of Ruthenium‐Based Metathesis Catalysts Bearing N‐Heterocyclic Carbene (NHC) Ligands,” Chemistry – A European Journal 7 (2001): 3236–3253, 10.1002/1521-3765(20010803)7:15<3236::AID-CHEM3236>3.0.CO;2-S. [DOI] [PubMed] [Google Scholar]
  • 27. Ackermann L., Fürstner A., Weskamp T., Kohl F. J., and Herrmann W. A., “Ruthenium Carbene Complexes With Imidazolin‐2‐ylidene Ligands Allow the Formation of Tetrasubstituted Cycloalkenes by RCM,” Tetrahedron Letters 40 (1999): 4787–4790, 10.1016/S0040-4039(99)00919-3. [DOI] [Google Scholar]
  • 28. Scholl M., Ding S., Lee C. W., and Grubbs R. H., “Synthesis and Activity of a New Generation of Ruthenium‐Based Olefin Metathesis Catalysts Coordinated With 1,3‐Dimesityl‐4,5‐dihydroimidazol‐2‐ylidene Ligands,” Organic Letters 1 (1999): 953–956, 10.1021/ol990909q. [DOI] [PubMed] [Google Scholar]
  • 29. Sanford M. S., Love J. A., and Grubbs R. H., “Mechanism and Activity of Ruthenium Olefin Metathesis Catalysts,” Journal of the American Chemical Society 123 (2001): 6543–6554, 10.1021/ja010624k. [DOI] [PubMed] [Google Scholar]
  • 30. Kingsbury J. S., Harrity J. P. A., Bonitatebus P. J., and Hoveyda A. H., “A Recyclable Ru‐Based Metathesis Catalyst,” Journal of the American Chemical Society 121 (1999): 791–799, 10.1021/ja983222u. [DOI] [Google Scholar]
  • 31. Love J. A., Sanford M. S., Day M. W., and Grubbs R. H., “Synthesis, Structure, and Activity of Enhanced Initiators for Olefin Metathesis,” Journal of the American Chemical Society 125 (2003): 10103–10109, 10.1021/ja027472t. [DOI] [PubMed] [Google Scholar]
  • 32. Garber S. B., Kingsbury J. S., Gray B. L., and Hoveyda A. H., “Efficient and Recyclable Monomeric and Dendritic Ru‐Based Metathesis Catalysts,” Journal of the American Chemical Society 122 (2000): 8168–8179, 10.1021/ja001179g. [DOI] [Google Scholar]
  • 33. Gessler S., Randl S., and Blechert S., “Synthesis and Metathesis Reactions of a Phosphine‐Free Dihydroimidazole Carbene Ruthenium Complex,” Tetrahedron Letters 41 (2000): 9973–9976, 10.1016/S0040-4039(00)01808-6. [DOI] [Google Scholar]
  • 34. Love J. A., Morgan J. P., Trnka T. M., and Grubbs R. H., “A Practical and Highly Active Ruthenium‐Based Catalyst That Effects the Cross Metathesis of Acrylonitrile,” Angewandte Chemie International Edition 41 (2002): 4035–4037, 10.1002/1521-3773(20021104)41:21<4035::AID-ANIE4035>3.0.CO;2-I. [DOI] [PubMed] [Google Scholar]
  • 35. Weskamp T., Schattenmann W. C., Spiegler M., and Herrmann W. A., “A Novel Class of Ruthenium Catalysts for Olefin Metathesis,” Angewandte Chemie International Edition 37 (1998): 2490–2493, 10.1002/(SICI)1521-3773(19981002)37:18<2490::AID-ANIE2490>3.0.CO;2-X. [DOI] [PubMed] [Google Scholar]
  • 36.Many attempts were made over the years to improve the atom economy as well as the safety profile by using carbene sources less hazardous than phenyldiazomethane; for some selected approaches, see ref. 37–47; for a review, see: Fogg D. and Foucault H., Comprehensive Organometallic Chemistry III. 11, ed. Crabtree R. H. and Mingos D. M. P. (Elsevier, 2007), 623–652. [Google Scholar]
  • 37. Belderrain T. R. and Grubbs R. H., “Reaction Between Ruthenium(0) Complexes and Dihalo Compounds. A New Method for the Synthesis of Ruthenium Olefin Metathesis Catalysts,” Organometallics 16 (1997): 4001–4003, 10.1021/om970514f. [DOI] [Google Scholar]
  • 38. Wilhelm T. E., Belderrain T. R., Brown S. N., and Grubbs R. H., “Reactivity of Ru(H)(H2)Cl(PCy3)2 With Propargyl and Vinyl Chlorides:  New Methodology To Give Metathesis‐Active Ruthenium Carbenes,” Organometallics 16 (1997): 3867–3869, 10.1021/om9705259. [DOI] [Google Scholar]
  • 39. Wolf J., Stüer W., Grünwald C., Werner H., Schwab P., and Schulz M., “Ruthenium Trichloride, Tricyclohexyl‐ phosphane, 1‐Alkynes, Magnesium, Hydrogen, and Water—Ingredients of an Efficient One‐Pot Synthesis of Ruthenium Catalysts for Olefin Metathesis,” Angewandte Chemie International Edition 37 (1998): 1124–1126, 10.1002/(SICI)1521-3773(19980504)37:8<1124::AID-ANIE1124>3.0.CO;2-C. [DOI] [PubMed] [Google Scholar]
  • 40. Gandelman M., Rybtchinski B., Ashkenazi N., Gauvin R. M., and Milstein D., “A New General Method for the Preparation of Metal Carbene Complexes,” Journal of the American Chemical Society 123 (2001): 5372–5373, 10.1021/ja0157393. [DOI] [PubMed] [Google Scholar]
  • 41. Poverenov E. and Milstein D., “Formation of Transition Metal Carbenes Using Haloalkylzinc Reagents,” Chemical Communications 30 (2007): 3189, 10.1039/b705459a. [DOI] [PubMed] [Google Scholar]
  • 42. Fürstner A., Liebl M., Lehmann C. W., et al., “Cationic Ruthenium Allenylidene Complexes as Catalysts for Ring Closing Olefin Metathesis,” Chemistry – A European Journal 6 (2000): 1847–1857, 10.1002/(SICI)1521-3765(20000515)6:10<1847::AID-CHEM1847>3.0.CO;2-1. [DOI] [PubMed] [Google Scholar]
  • 43. Fürstner A., Guth O., Düffels A., et al., “Indenylidene Complexes of Ruthenium: Optimized Synthesis, Structure Elucidation, and Performance as Catalysts for Olefin Metathesis—Application to the Synthesis of the ADE‐Ring System of Nakadomarin A,” Chemistry – A European Journal 7 (2001): 4811–4820, 10.1002/1521-3765(20011119)7:22<4811::AID-CHEM4811>3.0.CO;2-P. [DOI] [PubMed] [Google Scholar]
  • 44. Biberger T., Zachmann R. J., and Fürstner A., “Grubbs Metathesis Enabled by a Light‐Driven Gem ‐Hydrogenation of Internal Alkynes,” Angewandte Chemie International Edition 59 (2020): 18423–18429, 10.1002/anie.202007030. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 45. Zachmann R. J. and Fürstner A., “Light‐Driven Gem Hydrogenation: An Orthogonal Entry Into “Second‐Generation” Ruthenium Carbene Catalysts for Olefin Metathesis,” Chemistry – A European Journal 27 (2021): 7663–7666, 10.1002/chem.202101176. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 46. Saiegh T. J., Biberger T., Zachmann R. J., and Fürstner A., “Light‐Driven Alkyne Gem ‐Hydrogenation: An Intramolecular Approach to Hoveyda–Grubbs Catalysts,” Helvetica Chimica Acta 105 (2022): e202200133, 10.1002/hlca.202200133. [DOI] [Google Scholar]
  • 47. Boeda F., Clavier H., and Nolan S. P., “Ruthenium–Indenylidene Complexes: Powerful Tools for Metathesis Transformations,” Chemical Communications 24 (2008): 2726, 10.1039/b718287b. [DOI] [PubMed] [Google Scholar]
  • 48. Brook A. G. and Jones P. F., “The Synthesis of Silyl‐ and Germyldiazoalkanes via Tosylhydrazones,” Canadian Journal of Chemistry 47 (1969): 4353–4358, 10.1139/v69-720. [DOI] [Google Scholar]
  • 49. Han S. and Kass S. R., “Synthesis of 3‐aryl‐3‐trimethylsilylcyclopropenes and Their Dibenzoyl Derivatives. Possible Cyclopropenyl Anion Precursors? ” Journal of the Chemical Society, Perkin Transactions 1 1 (1999): 1553–1558, 10.1039/A900376B. [DOI] [Google Scholar]
  • 50. Ando W., Sekiguchi A., Rothschild A. J., et al., “Gas‐phase Pyrolysis of Phenyltrimethylsilyldiazomethane. Intramolecular Chemistry of Phenyltrimethylsilylcarbene,” Journal of the American Chemical Society 99 (1977): 6995–6999, 10.1021/ja00463a038. [DOI] [Google Scholar]
  • 51. Green S. P., Wheelhouse K. M., Payne A. D., Hallett J. P., Miller P. W., and Bull J. A., “Thermal Stability and Explosive Hazard Assessment of Diazo Compounds and Diazo Transfer Reagents,” Organic Process Research & Development 24 (2020): 67–84, 10.1021/acs.oprd.9b00422. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 52. Amoroso D., Snelgrove J. L., Conrad J. C., Drouin S. D., Yap G. P. A., and Fogg D. E., “An Attractive Route to Olefin Metathesis Catalysts: Facile Synthesis of a Ruthenium Alkylidene Complex Containing Labile Phosphane Donors,” Advanced Synthesis & Catalysis 344 (2002): 757, 10.1002/1615-4169(200208)344:6/7<757::AID-ADSC757>3.0.CO;2-X. [DOI] [Google Scholar]
  • 53. González‐Herrero P., Weberndörfer B., Ilg K., Wolf J., and Werner H., “The Sensitive Balance Between Five‐Coordinate Carbene and Six‐Coordinate Carbyne Ruthenium Complexes Formed From Ruthenium Vinylidene Precursors,” Organometallics 20 (2001): 3672–3685, 10.1021/om010422x. [DOI] [Google Scholar]
  • 54. Beach N. J., Jenkins H. A., and Spivak G. J., “Electrophilic Attack on [Cp*Cl(PPh3)Ru(CCHR)]:  Carbyne Formation vs Chloride Abstraction,” Organometallics 22 (2003): 5179–5181, 10.1021/om030559i. [DOI] [Google Scholar]
  • 55. Ledoux N., Drozdzak R., Allaert B., Linden A., Van Der Voort P., and Verpoort F., “Exploring New Synthetic Strategies in the Development of a Chemically Activated Ru‐based Olefin Metathesis Catalyst,” Dalton Transactions 44 (2007): 5201, 10.1039/b709994k. [DOI] [PubMed] [Google Scholar]
  • 56. Shao M., Zheng L., Qiao W., Wang J., and Wang J., “A Unique Ruthenium Carbyne Complex: A Highly Thermo‐Endurable Catalyst for Olefin Metathesis,” Advanced Synthesis & Catalysis 354 (2012): 2743–2750, 10.1002/adsc.201200119. [DOI] [Google Scholar]
  • 57.All components can also be mixed at the outset; in this case, the yield of 8 was slightly lower (70%); for details, see the Supporting Information.
  • 58. Grela K., Harutyunyan S., and Michrowska A., “A Highly Efficient Ruthenium Catalyst for Metathesis Reactions,” Angewandte Chemie International Edition 41 (2002): 4038–4040, 10.1002/1521-3773(20021104)41:21<4038::AID-ANIE4038>3.0.CO;2-0. [DOI] [PubMed] [Google Scholar]
  • 59. Nugent W. A., Feldman J., and Calabrese J. C., “Practical Catalyst for Cyclic Metathesis. Synthesis of Functional and/or Enantiopure Cycloalkenes,” Journal of the American Chemical Society 117 (1995): 8992–8998, 10.1021/ja00140a015. [DOI] [Google Scholar]
  • 60. Fürstner A. and Ackermann L., “A Most User‐Friendly Protocol for Ring Closing Metathesis Reactions,” Chemical Communications 1999 (1999): 95–96, 10.1039/a808810a. [DOI] [Google Scholar]
  • 61. Kim S.‐H., Zuercher W. J., Bowden N. B., and Grubbs R. H., “Catalytic Ring Closing Metathesis of Dienynes:  Construction of Fused Bicyclic [n. m.0] Rings,” Journal of Organic Chemistry 61 (1996): 1073–1081, 10.1021/jo951648a. [DOI] [Google Scholar]
  • 62. Fürstner A. and Langemann K., “Conformationally Unbiased Macrocyclization Reactions by Ring Closing Metathesis,” Journal of Organic Chemistry 61 (1996): 3942–3943, 10.1021/jo960733v. [DOI] [PubMed] [Google Scholar]
  • 63. Fürstner A. and Langemann K., “Macrocycles by Ring‐Closing Metathesis,” Synthesis 1997 (1997): 792–803, 10.1055/s-1997-4472. [DOI] [Google Scholar]
  • 64. Chatterjee A. K., Choi T. L., Sanders D. P., and Grubbs R. H., “A General Model for Selectivity in Olefin Cross Metathesis,” Journal of the American Chemical Society 125 (2003): 11360–11370, 10.1021/ja0214882. [DOI] [PubMed] [Google Scholar]
  • 65.To ensure good yields, isolated NHCs were used. Attempts at generating the NHC in situ from the corresponding (dihydro)imidazolium salt and a base resulted in much less clean conversions. However, alternative ways of generating the NHC in the presence of complex 2 can be conceived and are currenty under investigation.
  • 66. Lee C., Yang W., and Parr R. G., “Development of the Colle‐Salvetti Correlation‐energy Formula Into a Functional of the Electron Density,” Physical Review B: Condensed Matter and Materials Physics 37 (1988): 785–789, 10.1103/PhysRevB.37.785. [DOI] [PubMed] [Google Scholar]
  • 67. Becke A. D., “A New Mixing of Hartree–Fock and Local Density‐functional Theories,” Journal of Chemical Physics 98 (1993): 1372–1377, 10.1063/1.464304. [DOI] [Google Scholar]
  • 68. Weigend F., “Accurate Coulomb‐Fitting Basis Sets for H to Rn,” Physical Chemistry Chemical Physics 8 (2006): 1057, 10.1039/b515623h. [DOI] [PubMed] [Google Scholar]
  • 69. Weigend F. and Ahlrichs R., “Balanced Basis Sets of Split Valence, Triple Zeta Valence and Quadruple Zeta Valence Quality for H to Rn: Design and Assessment of Accuracy,” Physical Chemistry Chemical Physics 7 (2005): 3297, 10.1039/b508541a. [DOI] [PubMed] [Google Scholar]
  • 70. Grimme S., “Supramolecular Binding Thermodynamics by Dispersion‐Corrected Density Functional Theory,” Chemistry – A European Journal 18 (2012): 9955–9964, 10.1002/chem.201200497. [DOI] [PubMed] [Google Scholar]
  • 71. Garcia‐Ratés M. and Neese F., “Effect of the Solute Cavity on the Solvation Energy and Its Derivatives Within the Framework of the Gaussian Charge Scheme,” Journal of Computational Chemistry 41 (2020): 922–939, 10.1002/jcc.26139. [DOI] [PubMed] [Google Scholar]
  • 72. Neese F., “Software Update: The ORCA Program System—Version 6.0,” WIREs Computational Molecular Science 15 (2025): e70019, 10.1002/wcms.70019. [DOI] [Google Scholar]
  • 73. van der Eide E. F., Romero P. E., and Piers W. E., “Generation and Spectroscopic Characterization of Ruthenacyclobutane and Ruthenium Olefin Carbene Intermediates Relevant to Ring Closing Metathesis Catalysis,” Journal of the American Chemical Society 130 (2008): 4485–4491, 10.1021/ja710364e. [DOI] [PubMed] [Google Scholar]
  • 74. Macnaughtan M. L., Gary J. B., Gerlach D. L., Johnson M. J. A., and Kampf J. W., “Cross‐Metathesis of Vinyl Halides. Scope and Limitations of Ruthenium‐Based Catalysts,” Organometallics 28 (2009): 2880–2887, 10.1021/om800463n. [DOI] [Google Scholar]
  • 75. Nascimento D. L., Gawin A., Gawin R., et al., “Integrating Activity With Accessibility in Olefin Metathesis: An Unprecedentedly Reactive Ruthenium‐Indenylidene Catalyst,” Journal of the American Chemical Society 141 (2019): 10626–10631, 10.1021/jacs.9b05362. [DOI] [PubMed] [Google Scholar]
  • 76.The resulting stilbene derivative was detected by NMR and GC/MS. Bimolecular carbene coupling is known to be a major decomposition pathway of Grubbs‐type complexes, see ref. 77, 78 and the following: Bailey G. A., Foscato M., Higman C. S., Day C. S., Jensen V. R., and Fogg D. E., “Bimolecular Coupling as a Vector for Decomposition of Fast‐Initiating Olefin Metathesis Catalysts,” Journal of the American Chemical Society 140 (2018): 6931–6944, 10.1021/jacs.8b02709. [DOI] [PubMed] [Google Scholar]
  • 77. Amoroso D., Yap G. P. A., and Fogg D. E., “Deactivation of Ruthenium Metathesis Catalysts via Facile Formation of Face‐Bridged Dimers,” Organometallics 21 (2002): 3335–3343, 10.1021/om0110888. [DOI] [Google Scholar]
  • 78. Thiel V., Wannowius K.‐J., Wolff C., Thiele C. M., and Plenio H., “Ring‐Closing Metathesis Reactions: Interpretation of Conversion–Time Data,” Chemistry – A European Journal 19 (2013): 16403–16414, 10.1002/chem.201204150. [DOI] [PubMed] [Google Scholar]
  • 79. Fürstner A., Thiel O. R., Ackermann L., Schanz H. J., and Nolan S. P., “Ruthenium Carbene Complexes With N, N ′‐Bis(mesityl)Imidazol‐2‐ylidene Ligands:  RCM Catalysts of Extended Scope,” Journal of Organic Chemistry 65 (2000): 2204–2207, 10.1021/jo9918504. [DOI] [PubMed] [Google Scholar]
  • 80. Johns A. M., Fiamengo B. A., Herron J. R., et al., “Cis ‐Dichloro Sulfoxide Ligated Ruthenium Metathesis Precatalysts,” Organometallics 38 (2019): 218–222, 10.1021/acs.organomet.8b00895. [DOI] [Google Scholar]
  • 81. Forcina V., García‐Domínguez A., and Lloyd‐Jones G. C., “Kinetics of Initiation of the Third Generation Grubbs Metathesis Catalyst: Convergent Associative and Dissociative Pathways,” Faraday Discussions 220 (2019): 179–195, 10.1039/C9FD00043G. [DOI] [PubMed] [Google Scholar]
  • 82. Kang E.‐H., Lee I. S., and Choi T.‐L., “Ultrafast Cyclopolymerization for Polyene Synthesis: Living Polymerization to Dendronized Polymers,” Journal of the American Chemical Society 133 (2011): 11904–11907, 10.1021/ja204309d. [DOI] [PubMed] [Google Scholar]
  • 83. Kang E.‐H., Yu S. Y., Lee I. S., Park S. E., and Choi T.‐L., “Strategies to Enhance Cyclopolymerization Using Third‐Generation Grubbs Catalyst,” Journal of the American Chemical Society 136 (2014): 10508–10514, 10.1021/ja505471u. [DOI] [PubMed] [Google Scholar]
  • 84.For another study into parallel screening of different Grubbs‐type catalysts from this laboratory, see ref. 26 and the following: Reetz M. T., Becker M. H., Liebl M., and Fürstner A., “IR‐Thermographic Screening of Thermoneutral or Endothermic Transformations: The Ring‐Closing Olefin Metathesis Reaction,” Angewandte Chemie International Edition 39 (2000): 1236–1239, 10.1002/(SICI)1521-3773(20000403)39:7<1236::AID-ANIE1236>3.0.CO;2-J. [DOI] [PubMed] [Google Scholar]
  • 85.For the first example of a ruthenium carbene having the chloride ligands cis to each other, see: Prühs S., Lehmann C. W., and Fürstner A., “Preparation, Reactivity, and Structural Peculiarities of Hydroxyalkyl‐Functionalized "Second‐Generation" Ruthenium Carbene Complexes,” Organometallics 23 (2004): 280–287. [Google Scholar]
  • 86. 1H NMR spectra showed significant line broadening for the signals of trans‐41 indicative of rapid pyridine dissociation at RT, which is frozen out by lowering the temperature. In contrast, the signals of cis‐41 are sharp over the temperature range from 233 to 333K; for details, see the Supporting Information.

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Supporting File 1: anie71722‐sup‐0001‐SuppMat.pdf.

ANIE-65-e6803845-s001.pdf (5MB, pdf)

Data Availability Statement

The data that supports the findings of this study are available in the supplementary material of this article.

Articles from Angewandte Chemie (International Ed. in English) are provided here courtesy of Wiley

RESOURCES