The Mysteries of CAAC-bearing Sulfur-Chelated Ruthenium Precatalysts for Olefin Metathesis

Illya Rozenberg illya@post.bgu.ac.il Gabriel N. Lemcoff
Chemistry, Ben-Gurion University of the Negev, Beer-Sheva

Ruthenium-based precatalysts for olefin metathesis are among the most studied complexes in terms structure-activity relationship in the field of organometallic catalysis. All the ligands around the metal center have been modified with achievement of the significant impact on the catalyst’s stability, activity and selectivity. One of the reasons for the high success of this family of catalysts is the strong sigma electron donation of the N-heterocyclic carbene (NHC). Bertrand et al. have recently developed even stronger sigma donating ligands, the cyclic(alkyl)(amino)carbene ligands (CAAC).[1] Replacing the NHC by CAAC in olefin metathesis precatalysts by Bertrand and Grubbs led to a remarkable impact on stability and activity of the complexes.[2]

In our lab we developed latent precatalysts that are based on sulfur chelated to metal center and exist in two isomeric forms: inactive stable cis-Cl2 and reactive trans-Cl2. The activation of the complex to reactive form can be easily achieved by irradiation with 350nm light.[3] We have shown that the reason for the stability of the inactive form is the strong trans influence of the NHC ligand.[4] Thus, the use of this new ligand for our family of catalysts may lead to improving the properties of latency and activity at the same time. Herein, we present the synthesis and unexpected properties of sulfur-chelated complexes bearing CAAC ligands.

* X-ray structure was solved by Prof. Israel Goldberg, TAU

References:

[1] M. Soleilhavoup, G. Bertrand, Accounts of Chemical Research 2015, 48, 256-266

[2] D. R. Anderson, V. Lavallo, D. J. O`Leary, G. Bertrand, R. H. Grubbs, Angewandte Chemie International Edition 2007, 46, 7262-7265
V. M. Marx, A. H. Sullivan, M. Melaimi, S. C. Virgil, B. K. Keitz, D. S. Weinberger, G. Bertrand, R. H. Grubbs, Angewandte Chemie International Edition 2015, 54, 1919-1923.

[3] A. Ben-Asuly, A. Aharoni, C. E. Diesendruck, Y. Vidavsky, I. Goldberg, B. F. Straub, N. G. Lemcoff, Organometallics 2009, 28, 4652-4655
A. Aharoni, Y. Vidavsky, C. E. Diesendruck, A. Ben-Asuly, I. Goldberg, N. G. Lemcoff, Organometallics 2011, 30, 1607-1615

[4] C. E. Diesendruck, E. Tzur, A. Ben-Asuly, I. Goldberg, B. F. Straub, N. G. Lemcoff, Inorganic Chemistry 2009, 48, 10819-10825

Illya Rozenberg
Mr. Illya Rozenberg
Ben-Gurion University of the Negev








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