A Series of Dinuclear Copper Complexes Bridged by Phosphanylbipyridine Ligands: Synthesis, Structural Characterization and Electrochemistry

The phosphanylbipyridine ligands 6‐(diphenylphosphanyl)‐4,4′‐dimethyl‐2,2′‐bipyridine (PPh2‐Me2‐bipy, a), 4,4′‐di‐tert‐butyl‐6‐(diphenylphosphanyl)‐2,2′‐bipyridine (PPh2‐tBu2‐bipy, b), and 6‐(diisopropylphosphanyl)‐2,2′‐bipyridine (PiPr2bipy, c) and the corresponding dinuclear copper complexes [Cu2(...

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Bibliographic Details
Published in:European journal of inorganic chemistry 2013-08, Vol.2013 (22-23), p.4016-4023
Main Authors: Lilio, Alyssia M., Grice, Kyle A., Kubiak, Clifford P.
Format: Article
Language:English
Subjects:
Acetonitrile
Bridging ligands
Carbon dioxide
Coordination compounds
Copper
Cyclic voltammetry
Dimers
Dinuclear complexes
Electrochemistry
Ligands
Reduction
Synthesis
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Summary:The phosphanylbipyridine ligands 6‐(diphenylphosphanyl)‐4,4′‐dimethyl‐2,2′‐bipyridine (PPh2‐Me2‐bipy, a), 4,4′‐di‐tert‐butyl‐6‐(diphenylphosphanyl)‐2,2′‐bipyridine (PPh2‐tBu2‐bipy, b), and 6‐(diisopropylphosphanyl)‐2,2′‐bipyridine (PiPr2bipy, c) and the corresponding dinuclear copper complexes [Cu2(μ‐PPh2‐Me2‐bipy)2(NCCH3)2](PF6)2 (1), [Cu2(μ‐PPh2‐tBu2‐bipy)2(NCCH3)2](PF6)2 (2), [Cu2(μ‐PiPr2bipy)2(μ‐NCCH3)](PF6)2 (3), and [Cu2(μ‐PiPr2bipy)2{μ‐CNCH(CH3)2}](PF6)2 (4) were synthesized. The X‐ray structures of 1–4 show that the complexes are dinuclear with the bidentate bipyridine coordinating to one copper atom and the phosphane moiety coordinating the other copper center. Complexes 3 and 4 possess short Cu–Cu distances with bridging acetonitrile and isocyanide ligands. The cyclic voltammograms of 1–4 were examined under N2 and CO2. Under N2, 1–3 show four quasi‐reversible 1e– reductions, and under CO2, they show current enhancement at the second reduction. In comparison, complex 4 shows four irreversible reductions under N2 and no current enhancement under CO2. Three phosphanylbipyridine ligands that react with CuI to form dimeric complexes have been synthesized and structurally characterized. The Cu–Cu distance can be controlled by ligand substitution, and electrochemical studies of the dimers suggest that four sequential 1e– reductions of the bipyridine ligands occur. Catalytic behavior is observed under CO2.
ISSN:1434-1948
1099-0682
DOI:10.1002/ejic.201201208