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

Abstract Bis‐cyclometalated analogs of tris(2,2′‐bipyridine)ruthenium(II), namely [Ru III (C ∩ N) 2 (N ∩ N)]PF 6 complexes 3 , are prepared in 52–57 % yield from the mono‐cyclometalated N , N ‐dimethylbenzylamine (dmbaH) derivatives [Ru II (dmba)(N ∩ N)(MeCN) 2 ]PF 6 (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 C 1 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 Ru II/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)