A Periodic Walk: A Series of First-Row Transition Metal Complexes
with the Pentadentate Ligand PY5<sup>†</sup>
Robertus J. M. Klein Gebbink
Robert T. Jonas
Christian R. Goldsmith
T. Daniel P. Stack
10.1021/ic025617r.s002
https://acs.figshare.com/articles/journal_contribution/A_Periodic_Walk_A_Series_of_First-Row_Transition_Metal_Complexes_with_the_Pentadentate_Ligand_PY5_sup_sup_/3607416
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 (<b>1</b>−<b>6</b>) with cations of the general formula [M<sup>II</sup>(PY5)(Cl)]<sup>+</sup>, where M = Mn, Fe,
Co, Ni, Cu, Zn. In complexes <b>1</b>−<b>4</b> and <b>6</b>, 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 <b>5</b>, 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 <b>5</b>
with the other complexes reflects the strong tendency of PY5 to enforce a distorted-octahedral coordination geometry.
Complexes <b>1</b>−<b>6</b> 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.
2002-07-30 00:00:00
divalent oxidation state
nonsymmetrical pyridine subunit ligation
metal ions
PY 5 pocket
displacement
PY 5
ligand pocket increases
II
transition metal complexes