1553 Pure Appl. Chem., Vol. 79, No. 9, pp. 1553–1559, 2007. doi:10.1351/pac200779091553 © 2007 IUPAC Highly active organosilane-based N-heterocyclic carbene-palladium complex immobilized on silica particles for the Suzuki reaction* Sang-Myung Lee, Hyo-Jin Yoon, Jong-Ho Kim, Woo-Jae Chung, and Yoon-Sik Lee ‡ School of Chemical and Biological Engineering, Seoul National University, Seoul 151-744, Korea Abstract: 1-Methyl-3-(3-trimethoxysilylpropyl)imidazolium chloride, [TMSPIM][Cl – ], was synthesized as a precursor of N-heterocyclic carbene (NHC), which can be coordinated with palladium to give an organosilane-based bidentic NHC-Pd complex. The organosilane-based NHC-Pd complex was immobilized covalently on silica particles (NHC-Pd/silica) and then characterized by field emission/scanning electron microscopy (FE/SEM), transmission elec- tron microscopy (TEM), Fourier transform infrared spectroscopy (FTIRS), and inductively coupled plasma/atomic emission spectroscopy (ICP/AES). The Suzuki reaction was per- formed as a model reaction to examine the catalytic activity of NHC-Pd/silica. NHC-Pd/sil- ica exhibited excellent performance in the Suzuki reaction of various aryl halide derivatives (except for aryl chloride derivatives) with phenylboronic acid under mild conditions (room temperature and short reaction time). Moreover, the catalyst was recycled several times with- out any significant loss of catalytic activity in the Suzuki reaction. Keywords: N-heterocyclic carbene; Suzuki reaction; palladium; silica; organosilane. INTRODUCTION N-heterocyclic carbenes (NHCs) have emerged as an important research field since Öfele [1] disclosed originally in 1968. NHCs can be prepared in situ from the corresponding ionic liquids and readily co- ordinated with various transition metals affording stable and effective NHC-metal complexes. NHCs are very strong σ donors and show higher dissociation energies than phosphine ligands for a broad range of metals, so they do not easily dissociate from the metal center [2]. As with other ligands, NHCs can also stabilize catalytically relevant intermediates via electronic and steric effects [3]. Moreover, of par- ticular importance is the fact that NHCs are reliable and user-friendly due to air- and moisture-stability [4]. NHC-metal complexes are effective catalysts in many useful transformations, such as Suzuki, Heck, and Sonogashira coupling and aryl amination by NHC-Pd complexes [5], arylation and alkenyl- ation of aldehyde by NHC-Rh complexes [6], olefin metathesis, metathesis cross-coupling and hydro- formylation by NHC-Ru complexes [7], and Kumada coupling by NHC-Ni complexes [8]. Among the above-mentioned complexes, NHC-Pd complexes have been examined as the most significant catalysis *Paper based on a presentation at the 12 th International Conference on Polymers and Organic Chemistry 2006 (POC’06), 2–7 July 2006, Okazaki, Japan. Other presentations are published in this issue, pp. 1471–1582. ‡ Corresponding author