Synthesis and Characterization of Mononuclear, Pseudotetrahedral Cobalt(III) Compounds

Abstract

The preparation and characterization of two mononuclear cobalt(III) tropocoronand complexes, [Co(TC-5,5)](BF4) and [Co(TC-6,6)](BPh4), are reported. The cobalt(III) centers exist in rare pseudotetrahedral conformations, with twist angles of 65° and 74° for the [Co(TC-5,5]+ and [Co(TC-6,6)]+ species, respectively. Structural and electrochemical characteristics are compared with those of newly synthesized [Ga(TC-5,5)](GaCl4) and [Ga(TC-6,6)](GaCl4) analogues. The spin state of the pseudotetrahedral [Co(TC-6,6)](BPh4) compound was determined to be S = 2, a change in spin state from the value of S = 1 that occurs in the square-planar and distorted square-planar complexes, [Co(TC-3,3)](X) (X = BPh4, BAr′4) and [Co(TC-4,4)](BPh4), respectively.

New Perspectives for Aminotroponiminates: Coordination Chemistry, Redox Behavior, Cooperativity, and Catalysis

“…In this context, the lithium complex Li(ATI Ph/Ph ) should be mentioned, since an unusual Li–Ph contact was detected for this compound in the solid state (Figure b, bottom) . Finally, bridged ATIs and tropocoronands should formally also be mentioned in the category of ATI ligands with additional donor groups at N (Figure c) …”

“…Under oxidative conditions (+0.5 to +0.9 V), irreversible electron transfer has been observed for H‐ATI ligands and ATI or tropocoronand complexes of Na, Ga, Zn, Co, and Rh . These redox events were reasoned to be ligand‐centered, since they were observed for the ligands themselves or for complexes of metals that can be regarded as redox‐inactive under the applied conditions (Na, Ga, Zn).…”

“…These redox events were reasoned to be ligand‐centered, since they were observed for the ligands themselves or for complexes of metals that can be regarded as redox‐inactive under the applied conditions (Na, Ga, Zn). Ligand‐centered oxidations of cationic gallium compounds, [Ga(tropocoronand)] + , occurred at more positive potentials than those of the neutral zinc analogs, which can be attributed to the higher Lewis acidity of the Ga species . For compounds containing more than one ATI ligand and sulfonyl groups at the N ATI atoms, up to two additional irreversible, presumably ligand‐centered oxidation waves were reported in the range of +0.8 V to +1.1 V vs. Fe(C 5 H 5 ) 2 /[Fe(C 5 H 5 ) 2 ] + .…”

An Experimental and Theoretical Investigation on Pentacoordinated Cobalt(III) Complexes with an Intermediate S=1 Spin State: How Halide Ligands Affect their Magnetic Anisotropy

“…Diamagnetic Co III is mainly found in octahedral [18] and tetrahedral geometries, [19] or in tri- [20] and pentacoordinated [21] Co III complexes.T he less usual high spin state is found mainly in all types of geometry but in ad istorted and/orw eak-field environment. [18][19][20][21] Interestingly,t he Co III complexes with intermediate spin S = 1a re found mainly in square planar geometry, [19,22] and are attractive because of their remarkably large D magnitudes of up to 145 cm À1 . [23] Likewise, au nique distorted trigonal bipyramidal S = 1s ystem displaying a D value of + 107 cm À1 has also been reported.…”

Synthesis and characterization of Co(ii) and Fe(ii) peptide conjugates as hydrolytic cleaving agents and their preferential enantiomeric disposition for CT-DNA: structural investigation ofl-enantiomers by DFT and molecular docking studies

“…ESI-MS spectra of complexes exhibited some prominent peaks at m/z 782, 446 and 720 corresponding to [C 36 H 58 Thermogravimetric analysis was performed to examine the thermal decomposition behaviour of complexes under nitrogen atmosphere in the temperature range of 20-1000 C. The TGA prole of complexes showed 3 and 4 decomposition steps for Co(II) and Fe(II) complexes, respectively (Fig. ESI-MS spectra of complexes exhibited some prominent peaks at m/z 782, 446 and 720 corresponding to [C 36 H 58 Thermogravimetric analysis was performed to examine the thermal decomposition behaviour of complexes under nitrogen atmosphere in the temperature range of 20-1000 C. The TGA prole of complexes showed 3 and 4 decomposition steps for Co(II) and Fe(II) complexes, respectively (Fig.…”