Synthesis of transition metal complexes bearing bis-NHC ligands bridged by a thioether group
Abstract
The present work describes the synthesis of two novel bis-imidazolium salts (1 and 2) featuring a bridging thioether moiety prepared by the reaction of 1,4-bis{[2-(bromomethyl)phenyl]thio}butane with mesitylimidazole and methylimidazole under refluxing conditions. The new salts are air and moisture stable and they are highly soluble in polar solvents. Characterization of salts 1 and 2 was carried out through nuclear magnetic resonance of 1H and 13C nuclei and in case of salt 1, its structure was determined via x-Ray diffraction studies. Salts 1 and 2 were treated with excess of hexamethyldisilazane (KHMDS) and two equivalents of AuCl(SMe)2 or one equivalent of [Pd(allyl)Cl]2 providing the respective bis-carbenic gold(I) 3 and palladium(II) 4-5 complexes in excellent yields. The new metallic complexes were characterized via 1H and 13C-NMR spectroscopy. The palladium complexes 4-5, were preliminary tested as catalyst in the synthesis of biphenyl via a Suzuki cross-coupling process.
Downloads
References
Bierenstiel, M., Cross, E. D. (2011). Sulfur-functionalized N-heterocyclic carbenes and their transition metal complexes. Coordination Chemistry Reviews, 255(5-6), 574–590. DOI: 10.1016/j.ccr.2010.10.040
Braunstein, P., Naud, F. (2001). Hemilability of hybrid ligands and the coordination chemistry of Oxazoline-based systems. Angewandte Chemie International Edition, 40(4), 680–699. DOI: 10.1002/1521-3773(20010216)40:4%3C680::AID-ANIE6800%3E3.0.CO;2-0
Crabtree, R. H. (2013). Abnormal, mesoionic and remote N-heterocyclic carbene complexes. Coordination Chemistry Reviews, 257(3-4), 755–766. DOI: 10.1016/j.ccr.2012.09.006
Crudden, C. M., Allen, D. P., (2004). Stability and reactivity of N-heterocyclic carbene complexes. Coordination Chemistry Reviews, 248(21-24), 2247–2273. DOI: 10.1016/j.ccr.2004.05.013
Díez-González, S., Marion, N., Nolan, S. P. (2009). N-heterocyclic carbenes in late transition metal catalysis. Chemical Reviews, 109(8), 3612–3676. DOI: 10.1021/cr900074m
González-Sebastián, L., Morales-Morales, D. (2019). Cross-coupling reactions catalysed by palladium pincer complexes. A review of recent advances. Journal of Organometallic Chemistry, 893, 39–51. DOI: 10.1016/j.jorganchem.2019.04.021
Huynh, H. V., Yeo, C. H., Tan, G. K. (2006). Hemilabile behavior of a thioether-functionalized N-heterocyclic carbene ligand. Chemical Communications, (36), 3833. DOI: 10.1039/b608325k
Kühl, O. (2007). The chemistry of functionalised N-Heterocyclic Carbenes. Chemical Society Reviews, 36(4), 592–607. DOI: 10.1039/b603765h
Liu, G., Han, F., Liu, C., Wu, H., Zeng, Y., Zhu, R., Yu, X., Rao, S., Huang, G., Wang, J. (2019). A highly active catalyst system for Suzuki–Miyaura coupling of aryl chlorides. Organometallics, 38(7), 1459–1467. DOI: 10.1021/acs.organomet.8b00883
Meng, G., Kakalis, L., Nolan, S. P., Szostak, M. (2019). A simple 1H NMR method for determining the σ-donor properties of N-heterocyclic carbenes. Tetrahedron Letters, 60(4), 378–381. DOI: 10.1016/j.tetlet.2018.12.059
Normand, A. T., Cavell, K. J. (2008). Donor‐functionalised n‐heterocyclic carbene complexes of Group 9 and 10 metals in catalysis: Trends and directions. European Journal of Inorganic Chemistry, 2008(18), 2781–2800.
DOI: 10.1002/ejic.200800323
Scheldrick, G. M. (2014). SHELXS-2014: Program for the Solution of Crystal Structures, Institut Für Anorganishe Chemie, Göttingen, Germany
Selander, N., Szabó, K. J. (2010). Catalysis by Palladium Pincer Complexes. Chemical Reviews, 111(3), 2048–2076.
DOI: 10.1021/cr1002112
van der Sluis, P., Spek, A. L. (1990). Bypass: An effective method for the refinement of crystal structures containing disordered solvent regions. Acta Crystallographica Section A Foundations of Crystallography, 46(3), 194–201. DOI: 10.1107/s0108767389011189
Copyright (c) 2023 Emmanuel Campos-Dominguez, Daniel Mendoza-Espinoza, Simplicio González-Montiel
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
