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Tetranuclear Complexes Containing a Luminescent Ru 2 M 2 Core [M = Cu I , (allyl)Pd II ]: Synthesis, Structures and Electrochemical Properties
Author(s) -
Walther Dirk,
Böttcher Lars,
Blumhoff Jörg,
Schebesta Sebastian,
Görls Helmar,
Schmuck Katrin,
Rau Sven,
Rudolph Manfred
Publication year - 2006
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200501130
Subject(s) - chemistry , dication , ruthenium , crystallography , denticity , crystal structure , ligand (biochemistry) , bipyridine , stereochemistry , molecule , catalysis , organic chemistry , biochemistry , receptor
The reaction between [(tbbpy) 2 Ru(tmbiH 2 )](PF 6 ) 2 (tbbpy = 4,4′‐di‐ tert ‐butyl‐2,2′‐bipyridine; tmbiH 2 = 5,5′,6,6′‐tetramethyl‐2,2′‐dibenzimidazole) and LiMe/CuI affords the tetranuclear complex 1 containing the dication [{(tbbpy) 2 Ru(tmbi)} 2 Cu 2 ] 2+ . The X‐ray structure of 1 shows that the two [(tbbpy) 2 Ru(tmbi)] units coordinate the two Cu atoms in a twofold monodentate manner. Each copper atom is surrounded by two N‐donor atoms of different ruthenium( II ) units with N–Cu–N angles of 167.3°. The Cu ··· Cu separation (2.72 Å) indicates intranuclear contacts. LiMe/[(allyl)PdCl] 2 reacts with the starting Ru complex to form 2 , which contains the tetranuclear dication [{(tbbpy) 2 Ru(tmbi)} 2 {Pd(η 3 ‐allyl)} 2 ] 2+ . Its crystal structure shows that the Ru II units act as twofold monodentate ligands as well. Each Pd II is in an essentially planar coordination environment containing two nitrogen atoms of two different dibenzimidazolates in the cis position with the η 3 ‐bonded allyl group occupying the two remaining positions. In contrast to 1 , where the Ru–Cu–Cu–Ru unit forms an essentially planar structure, a strongly bent structure is formed in compound 2 . ESI mass spectra of 1 and 2 clearly show that the tetranuclear complexes are present in solution as well. Both complexes are luminescent. In addition, 2 catalyses the Heck coupling at 120 °C in N , N ‐dimethylacetamide. In contrast to 1 and 2 , the homodinuclear complex [(tbbpy) 2 Ru(tmbi)Ru(tbbpy) 2 ] ( 3 ) contains the dibenzimidazolate as a twofold chelating ligand that forms two five‐membered chelate rings with the Ru centres. Electrochemical measurements of 2 show two reversible, one‐electron oxidation steps, the difference between which (Δ E = 89 mV) is distinctly larger than the pure entropic effect. Furthermore, four reduction steps are observed, the first two of which are fully reversible. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)