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Abstract:
Polyalcohols (polyols), such as ethylene glycol, have mild reducing ability. They are used in the so-called polyol process to produce metallic nanoparticles of various kinds. In these syntheses, the effective reduction potential of the polyol strongly depends on the presence of other anions. Those anions compete against the polyol molecules for the direct bonding to the metal cations. As an indicator for the coordination behavior of polyols, we crystallized and structurally characterized 19 new coordination compounds with Mn, Co, Ni, Cu, Zn, Cd, Pb, or Bi. 15 of these compounds comprise nitrate ions, the others acetate ions. Compared to the already known chloride and sulfate analogues, nitrate shows an intermediate coordination affinity towards the metal cations considered here. While no direct metal–nitrate coordination occurs with Co 2+ , Ni 2+ , and Zn 2+ , mixed nitrate–polyol coordination environments are found for Mn 2+ , Cu 2+ , Cd 2+ , and Bi 3+ . Because of its strong chelating property, the acetate ion always coordinates the metal cation, competing with the polyol. The first mononuclear and dinuclear metal acetate diol coordination compounds were obtained with Co 2+ and Cu 2+ , respectively. The coordination affinity of nitrate and acetate ligands in solid metal polyol complexes fully corresponds with our recent observations of the anion-dependent reduction behavior of copper(II) salts in polyols. © 2019 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim
