Geometry and electronic structures of cobalt(II) and iron(III) complexes bearing bis(2-pyridylmethyl)ether or alkylbis(2-pyridylmethyl)amine

• Published in: Polyhedron 2022-05, Vol.218, p.115735, Article 115735
• Main Authors: Misawa-Suzuki, Tomoyo, Ikeda, Ryoto, Komatsu, Ryoya, Toriba, Ryo, Miyamoto, Ryo, Nagao, Hirotaka
• Format: Article
• Language: English
• Subjects: Cobalt; Electrochemistry; Iron; Tridentate ligand; X-ray diffraction
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2022.115735

Five- and six-coordinate cobalt(II) and six-coordinate iron(III) and complexes bearing tridentate bis(2-pyridylmethyl)ether (N,O,N-type) were synthesized and compared with those containing alkylbis(2-pyridylmethyl)amine (N,N,N-type). The geometrical and electrostatic differences of ether oxygen (sp2 hybridization) and amine nitrogen (sp3 hybridization) of tridentate ligands were studied. Electrochemical measurements revealed their distinctive redox behaviors. [Display omitted] •N,O,N-tridentate ligand, bis(2-pyridylmethyl)ether was used as a supporting ligand and coordinated to the cobalt or iron center.•Bis(2-pyridylmethyl)ether favored highly planar geometry.•Distinctive redox behaviors were revealed in organic solvents. Bis(2-pyridylmethyl)ether (bpme) was used as a tridentate ligand and coordinated to the cobalt(II) or iron(III) center for the development of new material conversion reaction centers. The structures and properties were investigated and compared to those of corresponding complexes bearing alkylbis(2-pyridylmethyl)amine (Rbpma; R = ethyl, benzyl). Reactions of the bpme ligand with CoIICl2·6H2O gave five-coordinate dichloridocobalt(II) complexes whereas those with FeIIICl3·6H2O afforded hexa-coordinate octahedral trichloridoiron(III) complexes. Octahedral cobalt(II) complexes containing two bpme ligands was isolated as well in a reaction with CoII(CH3COO)2·4H2O. All those complexes were in the high spin state at 295–298 K in the respective coordination geometry. Characteristic geometrical features around the metal center of bpme-containing complexes were discussed in comparisons with the corresponding Rbpma-containing complexes; [CoIICl2(bpme)] (1) was square pyramidal though [CoIICl2(Rbpma)] (R = ethyl; 2, benzyl; 3) was trigonal bipyramidal for five-coordinate compounds, and mer-[CoII(bpme)2](PF6)2 (4) and mer-[FeIIICl3(bpme)] (5) were meridional-type complexes while fac-[FeIIICl3(ebpma)] (6) was a facial-type compound for six-coordinate ones. It is noteworthy that distinctive redox behaviors were revealed in organic solvents.