Dissolution and reduction of cobalt ions in the polyol process using ethylene glycol: identification of the active species and its role

Matsumoto, Takatoshi; Takahashi, K.; Kitagishi, Keisuke; Shinoda, Kōzō; Huaman, Jhon L. Cuya; Piquemal, Jean‐Yves; Jeyadevan, Balachandran

doi:10.1039/c5nj00669d

Cited by 41 publications

(66 citation statements)

References 78 publications

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“…A strong coordination affinity had also been found for 3d metal chlorides, which always exhibit direct metal–chloride coordination . Chlorides of cobalt(II), nickel(II), and copper(II) cannot be reduced to metallic particles in boiling EG. These experimental findings can be explained by the formation of stable chlorido complexes, which prevent the reduction to the zero‐valent metal.…”

Section: Resultsmentioning

confidence: 99%

“…Thereby, the polyol molecules compete against other ligands, especially the anions of the metal salts used as starting materials. For example, using chloride salts of cobalt(II), nickel(II), and copper(II) as starting materials, does not lead to the formation of metallic particles. This might be rationalized by the chloride anion being a strong ligand that resides in the first coordination shell of the cation in solution and therefore prevents the reduction reaction.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Common Anions on the Coordination of Metal Cations in Polyalcohols

Teichert

Ruck

2019

Eur J Inorg Chem

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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 Co2+, Ni2+, and Zn2+, mixed nitrate–polyol coordination environments are found for Mn2+, Cu2+, Cd2+, and Bi3+. 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 Co2+ and Cu2+, 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.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Influence of Common Anions on the Coordination of Metal Cations in Polyalcohols

Teichert

Ruck

2019

Eur J Inorg Chem

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“…The Co 0 -hcp nanorods are formed by reducing cobalt(II) laurate in 1,2-butanediol containing NaOH and RuCl 3 . The influence of the concentration of NaOH, the carboxylate chain length, the cobalt precursor and the formation mechanism has been discussed in the literature [30,35,36]. Noble metals such as Ru are used as seeding agent to control the nucleation step in the formation of the particles, which finally translates into a control of the size of the particle.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Synthesis of cobalt nanodumbbells and their thermal stability under H2, H2/CO and O2 atmospheres

González-Carballo

Sadasivan

Landon

et al. 2016

Materials Characterization

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“…Systematic reduction experiments of cobalt(II) salts in EG revealed the importance of the type of anion and the deprotonation of the polyol for the progress of the reduction reaction. 10,11 Like cobalt and nickel, copper particles can be obtained in polyols at elevated temperature. Copper and copper oxide nanomaterials, as cheap alternatives to precious metals, have found wide attention with respect to their potential application in catalysis, photovoltaics, and optics in the last years.…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of the polyol reduction of copper(ii) salts depending on the anion type and diol chain length

2018

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The mechanisms of the polyol reduction of copper(ii) compounds were investigated by various systematic experiments. The course of the reduction in ethylene glycol strongly depends on the anion present in solution. Elemental copper can only be obtained in high yields starting from Cu(NO3)2, Cu(OAc)2, or Cu(OH)2; but not from CuCl2 or CuSO4. Intermediate compounds were observed, namely Cu2O, and the alkoxide compounds Cu(C2H4O2) and Cu3(OAc)2(C2H4O2)2. Cu3(OAc)2(C2H4O2)2 was characterised by single-crystal X-ray diffraction. It is a 2D coordination polymer with bridging bidentate acetate and bidentate deprotonated EG ligands leading to vertex- and edge-linked CuO5 polyhedra. Alkoxide compounds were also detected for higher glycol ethers. With growing glycol ether chain length the stability of alkoxide intermediates decreases, enhancing the stability range of Cu2O. Because the majority of copper species is precipitated as copper(ii) alkoxide compounds or Cu2O before the reduction to elemental copper occurs, only few nuclei are formed in solution leading to microparticles instead of nanoparticles. Much smaller but strongly agglomerated particles were observed under alkaline reaction conditions.

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Dissolution and reduction of cobalt ions in the polyol process using ethylene glycol: identification of the active species and its role

Abstract: The monoanionic state of ethylene glycol was theoretically and experimentally confirmed to be the active species during reduction reaction of metal salts.

Cited by 41 publications

References 78 publications

Influence of Common Anions on the Coordination of Metal Cations in Polyalcohols

Influence of Common Anions on the Coordination of Metal Cations in Polyalcohols

Synthesis of cobalt nanodumbbells and their thermal stability under H2, H2/CO and O2 atmospheres

Mechanisms of the polyol reduction of copper(ii) salts depending on the anion type and diol chain length

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