title: 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.
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.
authors: 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.
authors: Tatsuro
authors: T
authors: Toda
authors: Shigeki
authors: S
authors: Kuwata
authors: Takao
authors: T
authors: Ikariya
keywords: N ligands; carbenes; hydrogen bonds; ruthenium; tridentate ligands