Ruthenium olefin

The outstanding performances of five-membered NHC ligands in organometallic chemistry and catalysis prompted Grubbs and co-workers to develop a novel stable four-membered NHC [64]. Following their interest in developing new ruthenium olefin metathesis catalysts, they synthesised and fully characterised complex 51 to study the impact of the architecturally unique NHC ligand on the activity of the Ru-based catalyst [65] (Fig. 3.20). In the RCM of 1 at 40°C in CH Cl with 51 (5 mol% catalyst), the reaction reached completion within 20 min, whereas less than 10 min are required for standard catalysts 14 and 16. It should be noted that catalysts 14 and 16 are able to complete the RCM of 1 with only 1 mol% catalyst at 30°C. 

The pioneering work on enantioselective ruthenium olefin metathesis was carried out by Grubbs and co-workers in 2001 [69] (Fig. 3.23). Catalysts 55a-b and 56a-b were designed and prepared from C -symmetric NHC hgands with a combination of chiral backbone and mono-ortfto-substituted aryl side chains, a motif that was expected to form a chiral environment around the metal centre. 

Well-Defined Ruthenium Olefin Metathesis Catalysts Mechanism and Activity, ... 

Recent mechanistic work has shown that 16 e Ru methylene complexes (such as bisphosphine 11) are slow to re-enter the catalytic cycle. Their reluctance to initiate can result in competitive decomposition see Mechanism and Activity of Ruthenium Olefin Metathesis Catalysts, M.S. Sanford, J.A. Love, R.H. Grubbs,/. 

Trimmer, M. S. Commercial Applications of Ruthenium Olefin Metathesis Catalysts in Polymer Synthesis. In Handbook of Metathesis-, Grubbs, R. H., Ed. Wiley-VCH Weinheim, 2003 Vol. 3, pp 407-H8. 

Jack Halpern Perhaps I have more reason than anyone else to be disposed to the view that 7r-complexing is an important step of the insertion reaction, because I think that possibly we have the only reasonably clear cut case of an olefin insertion reaction where a complex is clearly implicated. This is the ruthenium chloride-catalyzed hydrogenation of certain olefins, which almost certainly involves the insertion of the olefin into a ruthenium hydrogen bond and where certainly a ruthenium olefin complex is involved as an observable reactant. Nevertheless, I am not at all sure to what extent this is a general or necessary feature of such insertion reactions. The important question is whether one or two coordination positions on the metal ion are involved in the transition state of the insertion reaction. For example, if one considers the insertion of an olefin, say into an M—X bond, then the transition state may look something like ... 

Reduction of ammonium chlororuthenate with titanous chloride gives a solution containing divalent ruthenium which will absorb ethylene or propylene to give a 1 1 ruthenium-olefin complex which was not isolated (108). Ethylene was previously reported not to form stable complexes on treatment with ruthenium halides (97). 

Water-soluble, aliphatic phosphines have been synthesized for their inclusion into ruthenium olefin metathesis catalysts (28). Complexes of the type... 

The ROMP of alcohol, ketone, halogen, and acetate substituted cyclooctenes with a ruthenium olefin metathesis catalyst has been reported (31). 

B. Mohr, D.M. Lynn, and R.H. Grubbs, Synthesis of water-soluble, aliphatic phosphines and their application to well-defined ruthenium olefin metathesis catalysts, Organometallics, 15(20) 4317 4325,1996. 

Fig. 2 Chronological order of ruthenium olefin metathesis catalysts...

P. E. Romero, W. E. Piers, and R. McDonald, Rapidly Initiating Ruthenium Olefin-Metathesis Catalysts, Angew. Chem. Int. Ed. 43, 6161-6165 (2004). 

Fig. 14. Two cbarge-tagged analogues of first generation ruthenium olefin metathesis catalysts (A and B). and the corresponding 14-electron active species observed by ESI(+)-MS (C) 71. ...

Scheme 18 Ruthenium olefin metathesis catalysts with C2-symmetric imidazolmiimi ligands...

Figure 6.3 Ruthenium olefin metathesis catalysts. Cy = cyclohexyl.

Vougioukalakis GC, Grubbs RH. Ruthenium olefin metathesis catalysts bearing an N-lluorophenyl-N-mesityl-substituted un-symmetrical N-heterocycUc carbene. Organometallics 2007 26 2469-2472. 

Jafarpour, L., Hillier, A. C., Nolan, S. P. Improved One-Pot Synthesis of Second-Generation Ruthenium Olefin Metathesis Catalysts. Organometallics 2002, 21,442-444. 

Dias, E. L., Nguyen, S. T., Grubbs, R. H. Well-Defined Ruthenium Olefin Metathesis Catalysts Mechanism and Activity. J. Am. Chem. Soc. 1997, 119, 3887-3897. 

Wagener, K.B. Lehman, S.E. Comparison of the kinetics of acyclic diene metathesis promoted by Grubbs ruthenium olefin metathesis catalysts. Macromolecules 2002, 35, 48-53. 

Evolution and applications of second-generation ruthenium olefin metathesis cartalysts , Schrodi, Y. and Pederson, R. L., Aldrichimica Acta, 2007, 40, 45. 

Seiders et al. reported that the enantioselective desymmetrization of the achiral triene 27 with the chiral ruthenium olefin metathesis catalyst 29 gave the dihydrofuran 28 with 90% ee (Scheme 10).91... 

Ruthenium-olefin complexes have been prepared by photochemical carbonyl displacement reactions ... 

The addition of olefinic compounds to the catalyst in solution corresponds to an uptake of I mole of olefin per mole of ruthenium(II), which apparently results in the formation of a 1 1 ruthenium-olefin 7r-complex. 

Evolution and applications of second-generation ruthenium olefin metathesis catalysts, particularly, using heterocyclic ligands 07AA45. 

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