Unsymmetrical Pincer‐Type Ruthenium Complex Containing β‐Protic Pyrazole and N‐Heterocyclic Carbene Arms: Comparison of Brønsted Acidity of NH Groups in Second Coordination Sphere |
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| Authors: | Tatsuro Toda Prof?Dr Shigeki Kuwata Prof?Dr Takao Ikariya |
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| Institution: | Department of Applied Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, O‐okayama, Meguro‐ku, Tokyo 152‐8552 (Japan), Fax: (+81)?3‐5734‐2637 |
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| Abstract: | A reaction of a 2‐(imidazol‐1‐yl)methyl‐6‐(pyrazol‐3‐yl)pyridine with RuCl2(PPh3)3] resulted in tautomerization of the imidazole unit to afford the unsymmetrical pincer‐type ruthenium complex 2 containing a protic pyrazole and N‐heterocyclic carbene (NHC) arms. Deprotonation of 2 with one equivalent of a base led to the formation of the NHC–pyrazolato complex 3 , indicating that the protic NHC arm is less acidic. When 2 was treated with two equivalents of a base under H2 or in 2‐propanol, the hydrido complex 4 containing protic NHC and pyrazolato groups was obtained through metal–ligand cooperation. |
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| Keywords: | carbenes hydrogen bonds N ligands ruthenium tridentate ligands |
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