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Published February 20, 2008 | Supplemental Material
Journal Article Open

Synthesis and Activity of Ruthenium Olefin Metathesis Catalysts Coordinated with Thiazol-2-ylidene Ligands


A new family of ruthenium-based olefin metathesis catalysts bearing a series of thiazole-2-ylidene ligands has been prepared. These complexes are readily accessible in one step from commercially available (PCy_3)_2Cl_2Ru CHPh or (PCy_3)Cl_2Ru CH(o-iPrO−Ph) and have been fully characterized. The X-ray crystal structures of four of these complexes are disclosed. In the solid state, the aryl substituents of the thiazole-2-ylidene ligands are located above the empty coordination site of the ruthenium center. Despite the decreased steric bulk of their ligands, all of the complexes reported herein efficiently promote benchmark olefin metathesis reactions such as the ring-closing of diethyldiallyl and diethylallylmethallyl malonate and the ring-opening metathesis polymerization of 1,5-cyclooctadiene and norbornene, as well as the cross metathesis of allyl benzene with cis-1,4-diacetoxy-2-butene and the macrocyclic ring-closing of a 14-membered lactone. The phosphine-free catalysts of this family are more stable than their phosphine-containing counterparts, exhibiting pseudo-first-order kinetics in the ring-closing of diethyldiallyl malonate. Upon removing the steric bulk from the ortho positions of the N-aryl group of the thiazole-2-ylidene ligands, the phosphine-free catalysts lose stability, but when the substituents become too bulky the resulting catalysts show prolonged induction periods. Among five thiazole-2-ylidene ligands examined, 3-(2,4,6-trimethylphenyl)- and 3-(2,6-diethylphenyl)-4,5-dimethylthiazol-2-ylidene afforded the most efficient and stable catalysts. In the cross metathesis reaction of allyl benzene with cis-1,4-diacetoxy-2-butene increasing the steric bulk at the ortho positions of the N-aryl substituents results in catalysts that are more Z-selective.

Additional Information

© 2008 American Chemical Society. Received August 15, 2007. Publication Date (Web): January 26, 2008. This research was supported in part by the National Institutes of Health and by a Marie Curie International Fellowship to G.C.V. within the 6th European Community Framework Programme. The authors would like to thank Larry M. Henling and Dr. Michael W. Day for the X-ray crystallographic analyses, Dr. Mona Shahgholi for performing the mass spectrometric analyses, and John B. Matson for assistance with the GPC analyses. Materia Inc. is also acknowledged for providing generous gifts of catalysts 2 and 4.

Attached Files

Supplemental Material - ja075849vsi20070803_084251.pdf

Supplemental Material - ja075849vsi20070803_084327.cif

Supplemental Material - ja075849vsi20070803_084347.cif

Supplemental Material - ja075849vsi20070803_084406.cif

Supplemental Material - ja075849vsi20070803_084419.cif


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