A Periodic Walk:  A Series of First-Row Transition Metal Complexes with the Pentadentate Ligand PY5

Abstract

A series of transition metal complexes derived from the pentadentate ligand PY5, 2,6-(bis-(bis-2-pyridyl)methoxymethane)pyridine, illustrates the intrinsic propensity of this ligand to complex metal ions. X-ray structural data are provided for six complexes (1-6) with cations of the general formula [M(II)(PY5)(Cl)](+), where M = Mn, Fe, Co, Ni, Cu, Zn. In complexes 1-4 and 6, the metal ions are coordinated in a distorted-octahedral fashion; the four terminal pyridines of PY5 occupy the equatorial sites while the axial positions are occupied by the bridging pyridine of PY5 and a chloride anion. Major distortions from an ideal octahedral geometry arise from displacement of the metal atom from the equatorial plane toward the chloride ligand and from differences in pyridine-metal-pyridine bond angles. The series of complexes shows that M(II) ions are consistently accommodated in the ligand by displacement of the metal ion from the PY5 pocket, a tilting of the axial pyridine subunit, and nonsymmetrical pyridine subunit ligation in the equatorial plane. The displacement from the ligand pocket increases with the ionic radius of M(II). The axial pyridine tilt, however, is approximately the same for all complexes and appears to be independent of the electronic ground state of M(II). In complex 5, the Cu(II) ion is coordinated by only four of the five pyridine subunits of the ligand, resulting in a square-pyramidal complex. The overall structural similarity of 5 with the other complexes reflects the strong tendency of PY5 to enforce a distorted-octahedral coordination geometry. Complexes 1-6 are further characterized in terms of solution magnetic susceptibility, electrochemical behavior, and optical properties. These show the high-spin nature of the complexes and the anticipated stabilization of the divalent oxidation state.

Synthesis and Characterization of New Azo 4,5-dimethyl-2-((3-((E)-1-(2-phenylhydrazono)ethyl)phenyl)diazenyl)-1H-imidazole and its Metal(II) Complexes

“…This is an important indication of coordination, therefore, the coloured complexes showed different characteristic absorption bands in their position and intensity [11,12].…”

Synthesis, Characterization, and Catalytic Activity of Iron(II) and Nickel(II) Complexes Containing the Rigid Pentadentate Ligand PY5Me2

“…The oxidation of cyclohexane via C-H bond activation with 1 was also investigated and the two products, cyclohexanol and cyclohexanone, were detected at 14 % and 11 % yield, respectively ( Table 2, entry 3), whereas the oxidation of styrene in acetone and acetonitrile gave benzaldehyde in 18 % and 9 % yield ( 2 , was generated. [15] To identify the active species in our system, the ESI/MS of 1 and 2 in the presence of excess H 2 O 2 was carried out in acetone.…”

“…[1] These ligands typically coordinate central metal atoms by one axial and four equatorial pyridine, imposing a square-pyramidal coordination arrangement, although other coordination modes have also been reported. [2,3] Moreover, they are able to reinforce an octahedral environment and restrict ligand substitution to a single coordination site. [4] These properties are particularly important in controlling the reactivity of kinetically labile first row metals.…”

Synthesis and Identification of Some New Metal Complexes of Mixed Schiff Base Ligands

“…Know the value of magnetic effective and electronic transition indicated the palladium complex is square planar geometry around the Palladium ion (31)(32)(33) ). The suggested geometry of the complexes was demonstrated at figures (13)(14)(15)(16)(17)(18). …”

“…The color of the prepared transition metal complexes are different from the color of their metal salts and ligands, this is good indication of coordination of the central metal ion through the donor atoms of their ligands, therefore the color of the prepared transition metal showed different characterization and positions ( [16][17]. electronic spectra of 2-(2-aminoethyl) isoindoline-1, 3-Dione.…”