Bis‐Ruthena(III)cycles [Ru(C^∩N)₂(N^∩N)]PF₆ as Low‐Potential Mediators for PQQ Alcohol Dehydrogenase (C^∩N = 2‐phenylpyridinato or 4‐(2‐tolyl)pyridinato, N^∩N = bpy or phen)

Abstract

Bis‐cyclometalated analogs of tris(2,2′‐bipyridine)ruthenium(II), namely [RuIII(C∩N)2(N∩N)]PF6 complexes 3, are prepared in 52–57 % yield from the mono‐cyclometalated N,N‐dimethylbenzylamine (dmbaH) derivatives [RuII(dmba)(N∩N)(MeCN)2]PF6 (N∩N = bpy or phen) and mercurated 2‐phenylpyridinato‐ or 4‐(2‐tolyl)pyridinato (C∩N) species Hg(C∩N)Cl. Two new bis‐ruthenacycles studied by X‐ray crystallography revealed a C1 symmetry, with the C and N atoms of different C∩N ligands trans to the nitrogen atoms of the N∩N ligand. The reduction potential of the RuII/III feature of 3 is as low as ca.–0.2 V (vs. SCE in MeCN). Complexes 3 display a unique mediating ability in moving electrons from the reduced active site of PQQ‐dependent alcohol dehydrogenase (PQQ‐ADH) to an electrode with 1,2‐propanediol as a substrate at a working potential of +0.1 V. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

A Highly Oxidizing and Isolable Oxoruthenium(V) Complex [RuV(N4O)(O)]2+: Electronic Structure, Redox Properties, and Oxidation Reactions Investigated by DFT Calculations

“…The E 1/2 values for Ru II/I couples are usually very negative for those Ru II complexes with N-donor ligands, but N-donor ligands are usually used to generate Ruoxo complexes in high oxidation states. [33] Also, the oneelectron reduction potentials of most Ru IV =O complexes reported in the literature are not high. [34] Together these contribute to why WNA has not been proposed for Ru IV =O systems.…”

Cycloruthenated Compounds – Synthesis and Applications

“…Thus, Yam et al reported higher values (1.66–1.86 V) for complexes 122a – d that bear an aminocarbene C,C ligand; on the basis of theoretical calculations, they considered that the HOMO involved in the irreversible oxidation process was not purely metal‐centred 186. Conversely, values in the –0.66 to –0.35 V range were found for ruthenium complexes 50a – d ,102 111 166,171,195,196 and 136b ,197 which are characterized by a high electron density at the metal, either because of anionic ancillary ligands or because of double cyclometallation.…”

“…Homoleptic bis‐chelated Ru III complexes 50 were similarly prepared by Ryabov et al102 starting from bis(solvato) cyclometallated complexes of Ru II and a chloridomercurated derivative of 2‐phenylpyridine (Scheme ): oxidation of the metal centre to the +3 oxidation states was caused by the inherent low Ru II /Ru III oxidation potential (from –0.21 to –0.25 V vs. SCE) of tris‐chelated Ru II species. It must be outlined that this method is the second known to date for the preparation of homoleptic OC ‐6 bisruthenacycles.…”

Heterolytic CH-bond activation in the synthesis of Ni{(2-aryl-κC2)pyridine-κN}2 and derivatives

“…In principle, an electrophilic metal center MX n can react with a chelate L-ArH to produce (L-Ar)MX nÀ1 and HX, where X is likely to be halide, OTf, O 2 CCF 3 , etc. Transition metal triflates are an attractive class of starting materials for an exploratory study of this type, and 2-phenyl-pyridine has considerable precedent in heterolytic CH-bond activations [8][9][10][11][12][13][14][15][16][17][18]. The use of Ni(OTf) 2 [19] as a starting material capable of heterolytically activating 2-phenyl-pyridine, and subsequent reactivity studies are reported herein.…”