DOI:10.1002/adsc.200700489 Hybrid Organic-Inorganic Materials from Di-(2-pyridyl)methyl- ACHTUNGTRENNUNGamine-PalladiumDichlorideComplexasRecoverableCatalysts forSuzuki,HeckandSonogashiraReactions MontserratTrilla, a Roser Pleixats, a, *MichelWongChiMan, b, * Catherine Bied, b andJolJ.E.Moreau b a ChemistryDepartment,UniversitatAutònomadeBarcelona,CerdanyoladelValls,08193Barcelona,Spain Fax:(+ 34)-9-3581-1265;e-mail:roser.pleixats@uab.es b Institut Charles Gerhardt Montpellier (UMR 5253 CNRS-UM2-ENSCM-UM1), Architectures MolØculaires et MatØriaux NanostructurØs,EcoleNationaleSupØrieuredeChimiedeMontpellier,8ruedel’Øcole normale, 34296-Montpellier cØdex 5,France Fax:(+ 33)-4-6714-7212;e-mail:michel.wong-chi-man@enscm.fr Received:October8,2007;Revised:December21,2007;Publishedonline:February25,2008 SupportinginformationforthisarticleisavailableontheWWWunderhttp://asc.wiley-vch.de/home/. Abstract: Hybrid silica materials containing the di- (2-pyridyl)methylamine-palladium dichloride com- plex, prepared by sol-gel cogelification, are efficient recyclable catalysts for Suzuki (aryl bromides and chlorides),Heck(arylbromides)andSonogashirare- actions (aryl iodides and bromides). Formation of palladium(0) nanoparticles is observed in the Suzuki and Heck reactions but not in the Sonogashira cou- pling. Keywords: catalyst immobilization; C À C coupling; organic-inorganic hybrid materials; palladium; sol- gel process Introduction Palladium-catalyzedcarbon-carbonbondformingpro- cesses such as the Suzuki–Miyaura [1] cross-coupling, Heck [2] and Sonogashira [3] reactions are key steps in the synthesis of natural products and a great variety of complex organic molecules used in many fields, such as drugs, agrochemicals or in materials science. On the other hand, the heterogenization of homoge- neous catalysts by their immobilization on polymeric organic [4] or inorganic [5] supports offers the advantag- es of easy product separation and catalyst recycling. Phosphanes are common ligands used in palladium- catalyzed processes, but they are readily oxidized to their corresponding phosphane oxides, which can pre- vent the easy recovery and reuse of the catalytic sys- tems. Thus, phosphane-free palladium catalysts have superiorstability. Some of us discovered [6] air- and moisture-stable phosphane-free macrocyclic triolefinic palladium(0) complexes. We have described their immobilization onto cross-linked polystyrene, [7] and onto a silica matrix, [8] and the activity of these supported versions as recyclable catalysts in Suzuki cross-couplings and telomerization reactions. However, the drawback of our heterogenized macrocyclic palladium(0) com- plexes was that they were efficient in Suzuki cou- plings with activated and deactivated aryl iodides but not for the more challenging aryl bromides and chlor- ides, the ideal substrates for coupling reactions being themoreeco-friendlyarylchlorides. [9] Several phosphane-free palladium systems have been reported as robust and efficient catalysts or pre- catalysts (high TON and TOF) [10] for the coupling re- actions with aryl chlorides (palladacycles, N-heterocy- clic carbenes and bipyridine-based systems). We fo- cused our attention on bipyridin-2-ylmethane-type li- gands to prepare immobilized palladium catalysts onto a silica matrix. Such inorganic supports consti- tute an interesting alternative for the preparation of heterogeneous catalysts because of their mechanical and thermal stability and chemical inertia. [11] The for- mationoforganic-inorganichybridsbysol-gelchemis- try [12] isaconvenientroutetosolidmaterialswithcat- alyticproperties. [5,13] Palladium(II) complexes of di-2-pyridylamine-de- rived ligands 1 (Figure1) have been developed by Buchmeiser [14] as catalysts for C À C and C À N bond formation and they have been covalently grafted to a matrix resulting from a ROMP polymerization. Adv. Synth. Catal. 2008, 350,577–590 #2008Wiley-VCHVerlagGmbH&Co.KGaA,Weinheim 577 FULL PAPERS