Synthesis and characterization of a metal coordination polymer consisting of ruthenium(III) beta-diketone units linked by butadiyne bridges

A new metal coordination polymer consisting of ruthenium(III) beta-diketone units linked by butadiyne bridges was synthesized, and two mononuclear com plexes, [Ru(mESima)(3)] and [Ru(mEma)(3)] (mESima(-) = 3-(trimethylsilyl)et hynyl-2,4-pentanedionate ion and mEma(-) = 3-ethynyl-2,4-pentanedionate ion ), were also prepared as starting materials for the polymerization. The pol ymer was soluble in dichloromethane, chloroform, and benzene. The number-av erage molecular weight, 5400, corresponding to about 11 monomer units, was obtained from the FT-NMR integrated intensities for the protons on the ethy nyl group of the mEma ligand end-group relative to the methyl protons of th e entire chains. The NMR spectra also showed that the polymer structure was not a star-burst type but a chain-like type. The polymer exhibited one oxi dation peak and one reduction peak on differential pulse voltammograms at 2 5 degrees C; however, the one anodic peak separated into two peaks at -36 d egrees C. The difference in peak potentials between the first and the secon d oxidation waves was 0.23 V, which was very similar to the difference (0.2 2 V) in peak potentials for the corresponding binuclear complex. This indic ated that metal-metal interactions in the polymer operate between only the closest neighboring units. Results of the controlled potential coulometry o f the polymer in dichloromethane medium indicated that each monomer unit un derwent a one-electron reduction. (C) 1999 Elsevier Science S.A. All rights reserved.