Monolith- and Silica-Supported Carboxylate-Based Grubbs± Herrmann-Type Metathesis Catalysts Jens O. Krause, b Said Lubbad, a Oskar Nuyken, b, * Michael R. Buchmeiser a, * a Institut f¸r Analytische Chemie und Radiochemie, Universit‰t Innsbruck, Innrain 52 a, 6020 Innsbruck, Austria Fax: (  43)-512-507-2677, e-mail: michael.r.buchmeiser@uibk.ac.at b Lehrstuhl f¸r Makromolekulare Stoffe, Technische Universit‰t M¸nchen, Lichtenbergstr. 4, 85747 Garching, Germany Fax: (  49)-89-289-13571, e-mail: oskar.nuyken@ch.tum.de Received: February12, 2003; Accepted: April4, 2003 Abstract: The synthesis of silica- and monolith- supported Grubbs±Herrmann-type catalysts is de- scribed. Two polymerizable, carboxylate-containing ligands, exo, exo-7-oxanorborn-2-ene-5,6-dicarboxylic anhydride and 7-oxanorborn-2-ene-5-carboxylic acid were surface-immobilized onto silica- and ring-open- ingmetathesis(ROMP-)derivedmonolithicsupports using ™grafting-from∫ techniques. The ™1 st generation Grubbs catalyst∫, RuCl 2 (  CHPh)(PCy 3 ) 2 , was used forthesepurposes.Inaddition,apoly(norborn-2-ene- b-exo, exo-norborn-2-ene-5,6-dicarboxylic anhydride) -coatedsilica60wasprepared.Thepolymersupport- ed anhydride and carboxylate groups were converted into the corresponding mono- and disilver salts, respectively, and reacted with the Grubbs±Herrmann catalyst RuCl 2 (  CHPh)(IMesH 2 )(PCy 3 ) [IMesH 2  1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2- ylidene]. Heterogenization was accomplished by ex- change of one chlorine ligand with the polymeric, immobilized silver carboxylates to yield monolith- supported catalysts 4, 5, and 6 as well as silica- supported systems 7, 8 and 9. The actual composition of these heterogenized catalysts was proven by the synthesis of a homogeneous analogue, RuCl[7-oxanor- bornan-2-(COOAg)-3-COO](  CHPh)(IMesH 2 )(PCy 3 ) (3). All homogeneous and heterogeneous catalysts were used in ring-closing metathesis (RCM) of diethyl diallylmalonate, 1,7-octadiene, diallyldiphen- ylsilane, methyl trans-3-pentenoate, diallyl ether, N,N-diallyltrifluoracetamide and t-butyl N,N-diallyl- carbamate allowing turnover numbers (TON×s) close to 1000. In a flow-through set-up, an auxiliary effect of pendant silver carboxylates was observed with catalyst 5, where the silver moiety functions as a (reversible) phosphine scavenger that both acceler- atesinitiationandstabilizesthecatalystbypreventing phosphine elution. Detailed catalytic studies were carried out with the monolith-supported systems 4 and 6 in order to investigate the effects of temper- ature and chain-transfer agents (CTA×s) such as cis- 1,4-diacetoxybut-2-ene. In all RCM experiments Ru- leaching was low, resulting in a Ru-content of the RCM products  3.5 mg/g(3.5ppm). Keywords: carboxylate ligands; heterogeneous catal- ysis; metathesis; polymers; ruthenium Introduction Hardlyanyotherfieldinsyntheticorganicchemistryhas experienced such a rapid development as transition metal-catalyzed C  C coupling reactions. [1±3] Among these,ring-closingmetathesis(RCM),crossandtandem metathesishavegainedastrongposition.InRCM, N- heterocyclic carbene(NHC)-based ruthenium benzyli- denes, [4±6] better known as ™2 nd generation Grubbs∫ or ™Grubbs±Herrmann∫catalysts,arenowinthecenterof interest. [7,8] Molybdenum-based Schrock carbenes [Mo(  N-2,6-R 2 -C 6 H 3 )(  CHCMe 2 Ph)(OCR×) 2 ] are still thecompoundsofpreferenceincasethereactionneeds tobecarriedoutinanasymmetricfashion. [9±15] Never- theless,theirrutheniumanaloguesarecharacterizedby an enhanced stability towards oxygen and protic com- pounds including water, which makes them in due consequencethecatalystsofchoicefornon-asymmetric RCM.ForheterogeneousRCM,wealreadyreportedon thesynthesisofmonolith-andsilica-supportedGrubbs± Herrmanncatalysts. [16,17] Thecatalyticsystemsdescribed there were obtained by heterogenization of a 1 st generation Grubbs catalyst via the NHC ligand, easily accomplished by an NHC/phosphine exchange. These supported catalysts were characterized by excellent stability, low Ru-bleeding and high turnover numbers (TON×s)upto280.Inoursearchforotherheterogenized metathesiscatalystswewereencouragedbythereports ofBuchowiczetal.andNieczyporetal.onmonomeric and supported carboxylate-derived 1 st generation Grubbs catalysts. [18,19] We therefore investigated the generalapplicabilityofahalogenexchangebetweena Grubbs±Herrmanncatalystandasupportedfunctional group,inparticularwithsilvercarboxylates. FULL PAPERS 996 ¹2003 WILEY-VCH Verlag GmbH&Co. KGaA, Weinheim DOI: 10.1002/adsc.200303037 Adv. Synth. Catal. 2003, 345,996±1004