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Four-Electron Oxidative Dehydrogenation Induced by Proton-Coupled Electron Transfer in Ruthenium(III) Complex with 2‑(1,4,5,6-Tetrahydropyrimidin-2-yl)phenolate
journal contribution
posted on 2013-09-03, 00:00 authored by Ryoji Mitsuhashi, Takayoshi Suzuki, Yukinari SunatsukiNew ruthenium(II or III) complexes
with general formula [Ru(O-N)(bpy)2]n+ (O-N = unsymmetrical bidentate phenolate ligand; bpy = 2,2′-bipyridine)
were synthesized, and their crystal structures and electrochemical
properties were characterized. RuII complexes with 2-(2-imidazolinyl)phenolate
(Himn–) or 2-(1,4,5,6-tetrahydropyrimidin-2-yl)phenolate
(Hthp–) could be deprotonated by addition of excess
KOtBu, although the deprotonated species
were easily reprotonated by exposure to air. Unlike these RuII complexes, their RuIII analogs showed interesting ligand
oxidation reactions upon addition of bases. With [RuIII(Himn)(bpy)2]2+, two-electron oxidation of
Himn– and reduction of the RuIII center
resulted in conversion of the 2-imidazolinyl group to a 2-imidazolyl
group. On the other hand, the corresponding Hthp– complex exhibited four-electron oxidation of the ligand to form
2-(2-pyrimidyl)phenolate (pym–). These aromatization
reactions of imidazolinyl and 1,4,5,6-tetrahydropyrimidyl groups were
also achieved by the electrochemically generated RuIII complexes.
