DOI: 10.1002/adsc.200505447 Hybrid-Bridged Silsesquioxane as Recyclable Metathesis Catalyst Derived from a Bis-Silylated Hoveyda-Type Ligand Xavier Elias, a Roser Pleixats, a, * Michel Wong Chi Man, b, * Joe ¨l J. E. Moreau b a Chemistry Department, Universitat Auto `noma de Barcelona, Cerdanyola del Valle `s, 08193 Barcelona, Spain Fax: ( þ 34)-93-581-1265, e-mail: roser.pleixats@uab.es b He ´te ´rochimie Mole ´culaire et Macromole ´culaire (UMR-CNRS 5076), Ecole Nationale Supe ´rieure de Chimie de Montpellier, 8 rue de l)e ´cole normale, 34296 Montpellier ce ´dex 5, France Fax: ( þ 33)-4-6714-7212, e-mail: michel.wong-chi-man@enscm.fr Received: November 17, 2005; Accepted: February 2, 2006 Supporting Information for this article is available on the WWW under http://asc.wiley-vch.de/home/. Abstract: The synthesis of a bis-silylated Hoveyda- type monomer is described as well as the preparation of several organic-inorganic hybrid materials derived from it by a sol-gel process (with and without tet- raethyl orthosilicate) and by anchoring to MCM-41. The resulting materials were treated with second gen- eration Grubbs) catalyst to generate second genera- tion Hoveyda–Grubbs-type alkylideneruthenium complexes covalently bonded to the silica matrix. These materials are recyclable catalysts for the ring- closing metathesis reaction of dienes and enynes. Keywords: catalyst immobilization; metathesis; organ- ic-inorganic hybrid materials; ruthenium; sol-gel proc- ess Introduction Olefinmetathesisconstitutesaverypowerful,mild,effi- cientandselectivemethodfortheruptureandreforma- tionofC  Cdoublebonds,widelyusedbyorganicchem- ists for the synthesis of a great variety of compounds. [1] Ring-closing enyne metathesis has also been explored inrecentyears,providing1-vinylcycloalkenederivatives from acyclic enynes in an atom economical process. [2] The enormous success of metathesis reactions during the last decade is due to the development of several well-defined metal alkylidenes. The second-generation Grubbs ruthenium catalysts [3] 1b, c (Figure 1) and spe- cially the Hoveyda–Grubbs catalysts [4] 2a, b (Figure 1) showenhancedreactivity,stabilityandrecoveryprofiles compared to the first generation Grubbs catalyst 1a (Figure 1), chelating styrenic ligands playing a role in such improvements. In the last years several research groups have dedicated their efforts to the preparation and testing of reusable metathesis catalysts, [5] one of themostusedrecyclingstrategiesbeingtheimmobiliza- tion of a robust and stable alkylidene complex on a pol- ymeric insoluble support. Filtration at the end of the re- action allows an easy separation of the product and re- covery of the catalyst, avoiding time-consuming chro- matography. Anchoring of ruthenium alkylidenes of type 1 and 2 tothepolymericmatrixhasbeenperformed via phosphine exchange, [6] via the N-heterocyclic car- bene ligand, [7] through halogen exchange, [8] or via alky- lidene exchange (boomerang-type catalysts). [9] Theeffi- ciency of boomerang-supported catalysts increases no- tably when Hoveyda-type chelating ligands are used. [10] Insoluble organic polymers are the supports most frequently found in the literature, although an- choring to soluble poly(ethylene glycol) [10a–c] and some recent examples of silica-bound alkylidene-ruthenium complexes have also been described. [6b,7c–e,8b–d,10f, g,j] The above-mentioned examples about silica-bound catalysts refer to anchoring to porous and non-porous silicasandtoglassnon-porousmonoliths.Thesol-gelhy- drolytic-condensation [11–13] of suitable organo-alkoxysi- lanes is a convenient method to synthesize solid hybrid materialswithtargetedproperties. [14–16] Severalorgano- metalliccomplexeshavebeenimmobilizedaccordingto this process to generate heterogeneous hybrid cata- lysts [17–19] and among these, bridged silsesquioxanes [20,21] appearedasanefficientroutetoproducethesecatalysts withahighandcontrolledloadingoftheorganicsdueto the preserved covalent Si  C bonds during the mild hy- drolysis-condensation reactions. [22] We want to present here our results concerning the preparation, the activity andtherecyclingofhybridorganic-inorganicsilicascon- taining second-generation Grubbs-Hoveyda-type ruthenium complexes, in the ring-closing metathesis FULL PAPERS Adv. Synth. Catal. 2006, 348,751–762 # 2006 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim 751