Student Poster Presentation #3 (Session 1)
Recoverable Ruthenium-Based Olefin Metathesis Catalysts via Host-
Guest Complexation
Brian A. Ondrusek and Hoyong Chung 1
1
Florida State University Department of Chemical and Biochemical Sciences
Abstract
The recovery and recycling of transition-metal based catalysts is important from the perspectives of practical
industrial use as well as green chemistry in general. Ruthenium-based olefin metathesis catalysts, specifically,
have become ubiquitous in research and industry alike and methods to improve their function are vigorously
sought after. Several methods have been developed to this end, such as adhesion to a stationary phase such as
silica or polymers, 1 the development of charged catalyst species for biphasic reactions, 2 as well as the preparation
of catalyst structures bound to thermomorphic polymers for recovery by precipitation. 3 Our research proposes a
different route by utilizing a photosensitive host-guest interaction to recover the desired catalyst from a
completed reaction. Tailoring an azobenzene moiety to the well-
known Hoveyda-Grubbs second-generation structure allows for
the recovery of the catalyst by interaction with a silica-supported
β-cyclodextrin host, the supramolecular interaction for which is
well understood. Our work has allowed us to synthesize the
desired catalyst (Figure 1) and test it in a sample of characteristic
reactions, showing activity comparable to that of the original H-
G catalyst. Synthesis of the cyclodextrin moiety proceeds
according to known procedures and results in a system which can
be controlled very easily by the cis/trans photoisomerization of
azobenzene, allowing us to attach/detach the catalyst at will and
recycle it in subsequent reactions. Future work in this area will
allow us to explore catalyst structures that are tailored for
different kinds of metathesis reactions, and well as expand into
reactions catalyzed by different transition metals such as
palladium and platinum. These kinds of recyclable catalysts have
the potential to reinvent the way that we think about using
Fig 1. Structure of the described catalyst
catalysts for chemical transformations on both the academic and
with tethered azobenzene functionality
industrial scale.
Reference
1. a) Allen DP, Van Wingerden MM, Grubbs RH. 2009. Well-Defined Silica-Supported Olefin Metathesis Catalysts.
Org Lett. 11: 1261. b) Mayr M, Wang D, Kröll R, Schuler N, Prühs S, Fürstner A, Buchmeiser MR. 2005. Monolithic
Disk-Supported Metathesis Catalysts for Use in Combinatorial Chemistry. Adv Synth Cat. 347: 484.
2. Klučiar M, Grela K, Mauduit M. 2013. Ruthenium-Based Complexes Containing a Benzimidazolium Tag Covalently
Connected to N-Heterocyclic Carbene Ligands: Environmentally Friendly Catalysts for Olefin Metathesis
Transformations. Dalton Trans. 42: 7354.
3. Hobbs C, Yang Y-C, Ling J, Nicola S, Su H-L, Bazzi HS, Bergbreiter DE. 2011. Thermomorphic Polyethylene-
Supported Olefin Metathesis Catalysts. Org Lett. 13: 3904.
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