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Protic NNN and NCN Pincer‐Type Ruthenium Complexes Featuring (Trifluoromethyl)pyrazole Arms: Synthesis and Application to Catalytic Hydrogen Evolution from Formic Acid
Author(s) -
Nakahara Yoshiko,
Toda Tatsuro,
Matsunami Asuka,
Kayaki Yoshihito,
Kuwata Shigeki
Publication year - 2018
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201701474
Subject(s) - chemistry , pincer movement , ruthenium , trifluoromethyl , deprotonation , protonation , catalysis , medicinal chemistry , formic acid , pyrazole , photochemistry , organic chemistry , ion , alkyl
Abstract NNN and NCN pincer‐type ruthenium(II) complexes featuring two protic pyrazol‐3‐yl arms with a trifluoromethyl (CF 3 ) group at the 5‐position were synthesized and structurally characterized to evaluate the impact of the substitution on the properties and catalysis. The increased Brønsted acidity by the highly electron‐withdrawing CF 3 pendants was demonstrated by protonation–deprotonation experiments. By contrast, the IR spectra of the carbonyl derivatives as well as the cyclic voltammogram indicated that the electron density of the ruthenium atom is negligibly influenced by the CF 3 group. Catalysis of these complexes in the decomposition of formic acid to dihydrogen and carbon dioxide was also examined. The NNN pincer‐type complex 1 a with the CF 3 group exhibited a higher catalytic activity than the t Bu‐substituted analogue 1 b . In addition, the bis(CF 3 ‐pyrazolato) ammine derivative 4 catalyzed the reaction even in the absence of base additives.