Proton-induced generation of remote N-heterocyclic carbene-Ru complexes.
The proton-induced Ru-C bond variation, which was previously found to be relevant in the water oxidation, has been investigated by using cyclometalated ruthenium complexes with three phenanthroline (phen) isomers. The designed complexes, [Ru(bpy)2 (1,5-phen)](+) ([2](+)), [Ru(bpy)2 (1,6-phen)](+) ([3](+)), and [Ru(bpy)2 (1,7-phen)](+) ([4](+)) were newly synthesized and their structural and electronic properties were analyzed by various spectroscopy and theoretical protocols. Protonation of [4](+) triggered profound electronic structural change to form remote N-heterocyclic carbene (rNHC), whereas protonation of [2](+) and [3](+) did not affect their structures. It was found that changes in the electronic structure of phen beyond classical resonance forms control the rNHC behavior. The present study provides new insights into the ligand design of related ruthenium catalysts.
Institute for Integrated Cell-Material Science, Kyoto University, Room 507, Advanced Chemical Technology Center in Kyoto, 105 Jibu-cho, Fushimi-ku, Kyoto 612-8374 (Japan).
Takashi
T
Fukushima
Ryoichi
R
Fukuda
Katsuaki
K
Kobayashi
Giovanni F
GF
Caramori
Gernot
G
Frenking
Masahiro
M
Ehara
Koji
K
Tanaka
bond theory; carbene ligands; density functional calculations; electronic structure; ruthenium