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

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 (CoCl2)-Cl-II center dot 6H(2)O gave five-coordinate dichloridocobalt(II) complexes whereas those with (FeCl3)-Cl-III center dot 6H(2)O afforded hexa-coordinate octahedral trichloridoiron (III) complexes. Octahedral cobalt(II) complexes containing two bpme ligands was isolated as well in a reaction with Co-II(CH3COO)(2)center dot 4H(2)O. 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; [(CoCl2)-Cl-II(bpme)] (1) was square pyramidal though [(CoCl2)-Cl-II(Rbpma)] (R = ethyl; 2, benzyl; 3) was trigonal bipyramidal for five-coordinate compounds, and mer-[Co-II(bpme(2)](PF6)(2) (4) and mer-[(FeCl3)-Cl-III(bpme)] (5) were meridional-type complexes while fac-[(FeCl3)-Cl-III(ebpma)] (6) was a facial-type compound for six-coordinate ones. It is noteworthy that distinctive redox behaviors were revealed in organic solvents.