Monomeric Square-Planar Cobalt(II) Acetylacetonate: Mystery or Mistake?

Abstract

No evidence was found for the existence of a previously reported mononuclear square-planar form of unsolvated cobalt(II) acetylacetonate, Co(acac)(2), in all samples that have been obtained by using a variety of preparative techniques and crystallization conditions. It was confirmed that the structure of tetramer Co(4)(acac)(8), reported back in 1964 by Cotton and Elder, is correct, the synthesis is reproducible, and the bulk material corresponds to single-crystal data. Additionally, the title compound can be isolated in tetranuclear form by reducing cobalt(III) acetylacetonate with cobalt metal in solvent-free conditions or by crystallization from a hexanes solution. At the same time, from noncoordinating halogenated solvents, Co(acac)(2) crystallizes as a trinuclear core molecule, in which all Co atoms also exhibit octahedral coordination. From coordinating solvents such as ethanol, cobalt(II) acetylacetonate was found to appear in the form of its bis-adduct Co(acac)(2)(EtOH)(2). On the basis of observations made in this work and the details presented in the original paper, we suggest that the reported mononuclear structure of square-planar acetylacetonate should likely contain copper instead of cobalt.

Crystal structure and magnetic properties of a linear tetranuclear CoIIcluster

“…There is a large family of tetranuclear Co II complexes, and most of these clusters have Co 4 O 4 cubane or defective dicubane cores (Habib et al, 2012;Gao et al, 2015;Scheurer et al, 2015;Ahmed et al, 2007;Zhang et al, 2011Zhang et al, , 2014. Only a few complexes possesses a linear tetranuclear Co II core (Barrios et al, 2009;Aguilà et al, 2011;Irving et al, 1975;Vreshch et al, 2010).…”

DiffractWD: an open-source program for powder pattern comparison and visualization

“…The user can copy the resulting image to the clipboard in vector form and use it for article preparation (Vreshch et al, 2010); an example is shown in Fig. 2.…”

catena-Poly[tris(μ3-acetylacetonato)nickelate(II)sodium(I)]

“…This has been observed in a variety of different systems (Yun et al, 1999;Lindoy et al, 1977;Rogachev et al, 2007;Castro et al, 1992). Within this class of compound, there is a special group where the M(acac) n units are coordinated to naked cations, producing heteropolymetallic complexes with different nuclearity and dimensionality (Shibata et al, 1984;Atencio et al, 2004;Greaney et al, 1975;Troyanov et al, 1999;Vreshch et al, 2010).…”