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Ruthenium-Based Olefin Metathesis Catalysts

Changes in Catalyst Architecture Offer Improved Productivity

Multiple examples of kilogram scale olefin metathesis processes described to date confirm that this technology can be successfully implemented after focused optimization efforts along with selection of a catalyst matching substrate and reaction conditions requirements.1 Many ruthenium-based olefin metathesis catalysts are now commercially available, facilitating metathesis technology application in both academia and industry.

Fine changes in the catalyst architectures often result in dramatic productivity improvements. For example, bulkier ligands shield the ruthenium metal center from unproductive coordination, effectively stabilizing the catalyst in the presence of otherwise troublesome functional groups.  In the conversion of A to B illustrated below, nitro-Grela (44-0758) is replaced with nitro-Grela-SiPr (44-0770). This simple change affords the desired product with a comparable yield but with 50 times lower catalyst loading and more than 5 times higher concentration.

Figure 1. Efficiency of ring closing metathesis depends of the catalyst selection and substrate preparation.

 figure 1

      Cathepsin K inhibitors

         Boehringer Ingelheim Int.

table 1

44-0758          44-0770           

Nitro-Grela complexes containing iodides on the other hand, stand out as efficient catalysts that are more stable than the parent catalyst and relatively tolerant to the presence of ethylene (and other impurities or by-products) during metathesis of terminal dienes.  Macrocyclization reaction via RCM is greatly improved by using nitro-Grela-SiMes-I2 over those of nitro-Grela complexes (Figure 2).

Figure 2

Figure 2. Improved efficiency of a ruthenium catalyst containing iodides in a macrocyclization reaction.

table 2 

image 3 

Apeiron chemists have developed a versatile set of ROMP catalysts, soluble in DCPD monomer, that provide precise control of ROMP initiation with thermal or chemical triggers (Figure 3). 20 ppm of HeatMet (44-0760) initiates the reaction at temperatures above 60oC to afford quantitative yields of poly(DCPD). LatMet (44-0753) is a latent catalyst that remains dormant in DCPD until its activation with hydrochloric acid, whereupon it affords full conversion within just 10 minutes. Mechanical properties of the resulting materials are in accordance with those representative for industrially produced and applied poly(DCPD).4

Figure 3. Ruthenium catalysts for efficient DCPD polymerization.

Figure 3

44-0753          44-0760   

Table 3

Workup simplicity is desired in any large-scale process.  Metathesis species from catalyst decomposition can lead to unwanted events such as double bond isomerization.  Several general solutions for residual ruthenium (and other metals) removal were established as seen in Figure 4.7 One of the options is the application of “self-scavenging catalysts” which were obtained by introduction of a quaternary ammonium group into the NHC backbone.  Application of ammonium-tagged complexes allows the removal of residual ruthenium by silica gel work-up, water extraction or simple precipitation.  In most cases, ruthenium levels in metathesis products were reduced from over 2000 to below 5 ppm.  Another approach that surpasses ruthenium contamination is catalyst immobilization.  To obtain more stable solid-supported catalysts, ammonium tagged complexes having bulkier NHC ligands (i.e. SIPr NHC) were prepared. Metal scavengers represent a more general method for metals removal.  Their use does not require structural modifications of the catalyst, allowing application of one scavenger with a wide variety of commercially available catalysts. SnatchCat (07-2203) has multiple advantages: (a) quick, irreversible, and quantitative binding of ruthenium (also efficient with palladium) (b) effective at small stoichiometric excess with respect to the catalyst; (c) easy removal of both the metal – scavenger complex and unbound scavenger; (d) compatible with broad range of functional groups and solvents; (e) easy to handle - stable, non-toxic, non-volatile, odor-free.  

Figure 4 Solution for efficient ruthenium removal.




Continuous development in the field of olefin metathesis is reflected in an increasing number of IP protected catalysts designed for specific processes.8 Optimized catalysts together with supportive technologies that help to surpass technical difficulties related to the metathesis reactions will successively facilitate implementation of new large-scale processes.



  1. (a) T. Nicola, M. Brenner, K. Donsbach, P. Kreye, Org. Process Res. Dev. 2005, 9, 513–515. (b) V. Farina, C. Shu, X.  Zeng, X. Wei, Z. Han, N.K.  Yee, C. H. Senanayake, Org. Process Res. Dev. 2009, 250–254.
  2. Boehringer Ingelheim Int. WO 2008/009671 A1
  3. A. Tracz, M. Matczak, K. Urbaniak & K. Skowerski, Beilstein J. Org. Chem. 2015, 11, 1823-1832
  4. (a) Polymer material property database EFUNDA ( ID=PDCP&MinorID=1); (b) C. Slugovc, “Industrial Applications of Olefin Metathesis Polymerization” in Olefin Metathesis: Theory and Practice, 1st ed. (Ed.: K. Grela), Wiley, Hoboken, Weinheim, 2014, p. 329– 333.
  5. A. Kozłowska, M. Dranka, M. Zachara, E. Pump, C. Slugovc, K. Skowerski, K. Grela, Chem. Eur. J. 2014, 20, 14120.
  7. (a) K. Skowerski, C. Wierzbicka, G. Szczepaniak, Ł. Gułajaski, M. Bieniek, K. Grela, Green Chem. 2012, 14, 3264 – 3268. (b) K.  Skowerski, J.  Pastva, S.  J. Czarnocki, J. Janoscova Org. Process Res. Dev. 201519, 872–877. (c) G. Szczepaniak, K. Urbaniak, C. Wierzbicka, K. Kosiński, K. Skowerski, K. Grela ChemSusChem 2015, 8, 4139-4148.
  8. David L. Hughes, Org. Process Res. Dev., 2016, 20 (6), pp 1008–1015


Products mentioned in this blog:

44-0758: [1,3-Bis(2,4,6-trimethylphenylimidazolidin-2-ylidene)]-(2-i-propoxy-5-nitrobenzylidene)ruthenium(II) dichloride nitro-Grela [502964-52-5]

44-0770: 1,3-Bis(2,6-di-i-propylphenyl)imidazolidin-2-ylidene)(2-i-propoxy-5-nitrobenzylidene) ruthenium(II) dichloride Nitro-Grela SiPr [928795-51-1]

44-0760: Dichloro(1,3-bis(2,4,6-trimethylphenyl)imidazolidin-2-ylidene){2-[(ethoxy-2-oxoethylidene)amino]benzylidene}ruthenium(II) HeatMet

44-0753: [1,3-Bis(2,4,6-trimethylphenylimidazolidin-2-ylidene)](tricyclohexylphosphine)-(2-oxobenzylidene)ruthenium(II) chloride LatMet [1407229-58-6]

07-2203: 1,4-Bis(2-isocyanopropyl)piperazine (SnatchCat Metal Scavenger) [51641-96-4]


 For related literature on Metathesis please see the links below:

Apeiron Metathesis Catalyst Kit

Selected Ruthenium Metathesis Catalysts

Metathesis Catalysts and Ligands

The Strem Chemiker – Vol. XXVII No. 1 – June 2015 Olefin Metathesis



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