Magnetic Study of a Pentanuclear {Co₂^IIICo₃^II} Cluster with a Bent {Co^II₃} Motif

Abstract

Keywords: Cluster compounds / Cobalt / Mixed-valent compounds / Magnetic properties / Density functional calculations / EPR spectroscopyWe have synthesised and structurally characterised a new pentanuclear mixed-valent cobalt cluster of formula [Co II 3 Co III 2 (OH) 2 (piv) 6 (L) 2 (H 2 O) 4 ] (piv = trimethylacetate, H 2 L = salicylideneanthranillic acid) from reaction of a dinuclear cobalt pivalate precursor with a Schiff base type ligand under mild reaction conditions. The core structure can be conveniently described as two fused Co 3 -μ 3 -OH triangles with a strict unique sharing vertex point. A complete picture of the magnetic behaviour of this compound is presented. Through combined use of susceptibility, magnetisation, and[a]

{CoII/III5} horseshoe and {NiII4} lacunary cubane coordination clusters: the isobutyrate/N-butyldiethanolamine reaction system

“…We note that in 2015 Lazzarini et al 13 described a bent mixed-valent {Co II 3 Co III 2 } complex with the Co II -Co II -Co II angle of 138.98(1) that was obtained in 8% yield by reacting a [Co 2 (H 2 O)(piv) 4 (Hpiv) 4 ] precursor (Hpiv ¼ pivalic acid) with a Schiffbase ligand and triethylamine in MeCN. Contrary to compound 1 bearing two different types of ligands (carboxylate and aminoalcohol) and a metal core with alternating Co(II) and Co(III) centers, the pentanuclear {Co II 3 Co III 2 } core in the reported complex consists of three inner cobalt(II) atoms and two terminal cobalt(III) atoms and is supported by six m-carboxylate ligands, two Schiff-base ligands, two m 3 -OH groups and four terminal water molecules that complete the octahedral coordination of some Co(II) centers.…”

“…The lacunary cubane structure of 2 was hitherto not known as discrete motif; 1 represents an entirely different Co II/III valence pattern compared to the only other known {Co II/III 5 } horseshoe cluster. 13 The ligand environments at certain metal sites are in principle conducive to facile metathesis, an important aspect for a potential catalytic functionality that we plan to explore in the future.…”

Structures and Magnetostructural Correlation Analyses for Two Novel Hexanuclear Complexes Based on a Pentadentate Schiff Base Ligand

“…At 300 K, the χ M T value is 13 cm 3 ⋅K⋅mol ‐1 , considerably higher than the calculated value (7.5 cm 3 ⋅K⋅mol ‐1 ) of four spin‐only Co II centres ( S i = 3/2, g=2), which probably are attributed to the orbital contribution. To achieve the observed χ M T value at 300 K, the g value should be 2.63, indicating that orbital contribution is non‐negligible . Upon cooling, the χ M T increases much gradually to the value of 15.9 cm 3 ⋅K⋅mol ‐1 at 24 K before rapidly goes up to the maximum (26.9 cm 3 ⋅K⋅mol ‐1 ) at 10 K. This variation reveals the occurrence of the ferromagnetic coupling between the Co II ions through the EO‐N 3 − and μ 2,3 ‐O path.…”

Synthesis, structure, and properties of a pentanuclear cobalt(III) coordination cluster

“…Self-assembly of this type of dinuclear complex via formation of additional bridges by the ancillary ligands of the primary dinuclear unit or by small bridging ligands can lead to extended polynuclear coordination clusters involving additional metal cations [13][14][15][16][17]. The magnetic properties of cobalt(II) have led to considerable interest in cobalt(II) coordination clusters as single molecule magnets [10,11,[17][18][19][20][21][22][23][24][25]. In an attempt to prepare a coordination cluster using cobalt(II) acetate and the acyclic compartmental Schiff base 2,6-bis((3-aminopropylimino)methyl)-4-methylphenol, we have isolated the diamagnetic pentanuclear cobalt(III) species…”