R. H. Grubbs, A. G. Wenzel, and D. O'leary, Selected comprehensive books on olefin metathesis: (a) Handbook of Metathesis, 2014.

P. Schwab, R. H. Grubbs, and J. W. Ziller, The Influence of the Alkylidene Moiety on Metathesis Activity. Synthesis and Applications of RuCl 2 (=CHR'(PR 3 ) 2, J. Am. Chem. Soc, vol.118, pp.100-110, 1996.

C. S. Higman, J. A. Lummiss, . D. Fogg, D. Hughes, P. Wheeler et al., Olefin Metathesis at the Dawn of Implementation in Pharmaceutical and Specialty-Chemicals Manufacturing, industry, see: (a), vol.55, pp.3552-3565, 1938.

, Cheng-Sánchez, I.; Sarabia. F. Recent Advances in Total Synthesis via Metathesis Reactions, Angew. Chem. Int. Ed, vol.44, pp.3749-3786, 2005.

E. L. Dias, S. T. Nguyen, and . R. Grubbs, Well-Defined Ruthenium Olefin Metathesis Catalysts: Mechanism and Activity

M. Scholl, S. Ding, C. W. Lee, and R. H. Grubbs, Synthesis and Activity of a New Generation of Ruthenium-Based Olefin Metathesis Catalysts Coordinated with 1,3-Dimesityl-4,5-dihydroimidazol-2-ylidene Ligand, J. Am. Chem. Soc, vol.119, pp.953-956, 1997.

R. Kadyrov and W. L. Mcclennan, For recent investigations concerning catalyst degradation, see: (a) Kadyrov, R. Low Catalyst Loading in Ring-Closing Metathesis Reactions, Chem. Eur. J, vol.19, pp.113-116, 2013.

J. A. Lummiss, . D. Fogg, C. S. Higman, A. E. Lanterna, M. L. Marin et al., General Decomposition Pathway for Phosphine-Stabilized Metathesis Catalysts: Lewis Donors Accelerate Methylidene Abstraction, Key Processes in Ruthenium-Catalysed Olefin Metathesis, vol.138, pp.10355-10375, 2014.

A. Demonceau, A. F. Noels, E. Saive, and A. J. Hubert, Closely related, PPh 3 ligated catalysts were synthesized previously by Baird and Bennet: (b) Zelonka, R. A.; Baird. M. C. Benzene Complexes of Ruthenium(II), Canadian Journal of Chemistry, vol.76, pp.145381-145404, 1972.

W. A. Herrmann, M. Elison, J. Fischer, C. Kocher, . G. Artus et al., Generation under Mild Conditions and Formation of Group 8-10 Transition Metal Complexes Relevant to Catalysis, Chem. Eur. J, vol.2, pp.772-780, 1996.

L. Jafarpour, J. Huang, E. D. Stevens, and S. P. Nolan, (p-cymene)RuLCl 2 (L = 1,3-Bis(2,4,6-trimethylphenyl)imidazol-2-ylidene and 1,3-Bis(2,6-diisopropylphenyl)imidazol-2-ylidene) and Related Complexes as Ring Closing Metathesis Catalysts, Organometallics, vol.18, pp.3760-3763, 1999.

J. Engel, W. Smit, M. Foscato, G. Occhipinti, K. W. Törnroos et al., Loss and Reformation of Ruthenium Alkylidene: Connecting Olefin Metathesis, Catalyst Deactivation, Regeneration, and Isomerization, J. Am. Chem. Soc, vol.139, pp.16609-16619, 2017.

C. S. Fogg and D. E. , High-Yield Synthesis of a Long-Sought, Labile Ru-NHC Complex and Its Application to the Concise Synthesis of Second-Generation Olefin Metathesis Catalysts, Organometallics, vol.37, pp.4551-4555, 2018.

, For an excellent review concerning Ru-arene catalysts, see: Delaude, L.; Demonceau, A. Retracing the Evolution of Monometallic Ruthenium-Arene Catalysts for C-C Bond Formation, Dalton Trans, vol.41, pp.9257-9268, 2012.

A. Demonceau, A. W. Stumpf, E. Saive, A. F. Noels, D. Jan et al., Synthesis and Evaluation of New RuCl 2 (pcymene)(ER 2 R?) and (? 1 : ? 6 -phosphinoarene)RuCl 2 Complexes as Ring-Opening Metathesis Polymerization Catalysts, J. Mol. Cat. A: Chemical, vol.30, pp.203-215, 1997.

M. Ahr, C. Thieuleux, C. Copéret, B. Fenet, and J. Basseta,

&. Noels, J. Grubbs-;-louie, and R. H. Grubbs, Catalysts: Evidence for One Unique Active Species for Two Different Systems, Highly Active Metathesis Catalysts Generated In Situ from Inexpensive and Air-Stable Precursors, vol.349, pp.1587-1591, 2007.

D. Sémeril, C. Bruneau, P. H. Dixneuf, X. Ruthenium-catalyst-dichotomy-;-sauvage, Y. Borguet et al., New In Situ Generated Ruthenium Catalysts Bearing N-Heterocyclic Carbene Ligands for the Ring-Opening Metathesis Polymerization of Cyclooctene, Selective Catalytic Diene Cycloisomerization or Metathesis, vol.40, pp.684-688, 1999.

A. W. Stumpf, E. Saive, A. Demonceau, and A. F. Noels, 1127-1128 and ref. 12a. For a failed attempt to synthesize Ru-5, see: c) Ledoux, N.; Allaert, B.; Verpoort F. Ruthenium-Based NHC-Arene Systems as Ring-Opening Metathesis Polymerisation Catalysts, Eur. J. Inorg. Chem, pp.5578-5583, 1995.

, Grubbs already reported that

, See Supporting Information (SI) for additional screening experiments. (21) ESI mass spectrometry the Ru-stock solution confirmed the presence of Ru-6 (see SI)

W. M. Sherrill, R. Kim, and M. Rubin, Improved Preparative Route Toward 3-Arylcyclopropenes, A4 can be easily prepared on large scale, see: (a), vol.64, pp.8610-8617, 2008.

D. S. Müller, I. Marek, D. S. Müller, I. Marek, D. S. Müller et al., Asymmetric Copper-Catalyzed Carbozincation of Cyclopropenes en Route to the Formation of Diastereo-and Enantiomerically Enriched Polysubstituted Cyclopropanes, Cyclopropenes show similar reactivity than alkynes: (b), vol.45, pp.3970-3973, 2015.

C. Grünwald, G. Gevert, J. Wolf, P. Bonzález-herrero, and H. Werner, Five-Coordinate 16-Electron Carbeneand Vinylideneruthenium(II) Complexes Prepared from

, b) For a mechanistic study concerning the formation of metal vinylidenes from alkynes, see: Wakatsuki, Y.; Mechanistic Aspects Regarding the Formation of Metal Vinylidenes from Alkynes and Related Reactions, J. Organomet. Chem, vol.15, pp.4092-4109, 1960.

Y. Borguet, X. Sauvage, G. Zaragoza, A. Demonceau, L. Delaude et al., Synthesis and Catalytic Evaluation in Olefin Metathesis of a Second-Generation Homobimetallic Ruthenium-Arene Complex Bearing a Vinylidene Ligand, Organometallics, vol.29, pp.2730-2738, 2010.

L. K. Johnson, R. H. Grubbs, and J. W. Ziller, Synthesis of Tungsten Vinyl Alkylidene Complex via the Reactions of WCl 2 (NAr)(PX 3 ) 3 (X = R, OMe) Precursors with 3,3-Disubstituted Cyclopropenes, J. Am. Chem. Soc, vol.115, pp.8130-8145, 1993.

S. T. Nguyen, L. K. Johnson, and R. H. Grubbs, Ring-Opening Metathesis Polymerization (ROMP) of Norbornene by a Group VIII Carbene Complex in Protic Media, J. Am. Chem. Soc, vol.114, pp.3974-3975, 1992.

, Noels demonstrated previously that it is important to add the ruthenium-arene complex to the activator and the substrate, see ref. 6a

E. Galardon, P. Le-maux, L. Toupet, and G. Simonneaux, 20-Tetraphenylporphyrinato)ruthenium(II) (Diethoxycarbonyl)carbene Methanol, Synthesis, Crystal Structure, and Reactivity, vol.10, issue.5, pp.565-569, 1998.

M. Michrowska, A. Usanov, D. L. Grela, and K. , In an Attempt to Provide a User's Guide to the Galaxy of Benzylidene, Alkoxybenzylidene and Indenylidene Ruthenium Olefin Metathesis Catalysts, Chem. Eur. J, vol.14, pp.806-818, 2008.

D. S. Müller, I. Curbet, Y. Raoul, J. Le-nôtre, O. Baslé et al., Stereoretentive Olefin Metathesis Made Easy: In Situ Generation of Highly Selective Ruthenium Catalysts from Commercial Starting Materials, RCM reactions producing macrocycles, for example, vol.20, pp.6822-6826, 2018.

E. Solari, S. Gauthier, R. Scopelliti, and K. Severin, Multifaceted Chemistry of [(p-cymene)RuCl 2 ] 2 and PCy 3, Organometallics, vol.28, pp.4519-4526, 2009.

J. Allard, I. Curbet, G. Chollet, F. Tripoteau, S. Sambou et al., Bleaching Earths as Powerful Additives for Ru-Catalyzed Self-Metathesis of Non-Refined Methyl Oleate at Pilot Scale, Chem. Eur. J, vol.23, pp.12729-12734, 2017.
URL : https://hal.archives-ouvertes.fr/hal-01614771

M. B. Dinger and J. C. Mol, High Turnover Numbers with Ruthenium-Based Metathesis Catalysts, Adv. Synth. Catal, vol.344, pp.671-677, 2002.