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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
Author(s) -
Toda Tatsuro,
Kuwata Shigeki,
Ikariya Takao
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201403179
Subject(s) - pincer movement , chemistry , carbene , pyrazole , deprotonation , ruthenium , imidazole , medicinal chemistry , tautomer , ligand (biochemistry) , pyridine , catalysis , stereochemistry , organic chemistry , ion , biochemistry , receptor
A reaction of a 2‐(imidazol‐1‐yl)methyl‐6‐(pyrazol‐3‐yl)pyridine with [RuCl 2 (PPh 3 ) 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 H 2 or in 2‐propanol, the hydrido complex 4 containing protic NHC and pyrazolato groups was obtained through metal–ligand cooperation.