Fe–N vs Fe–X (X indicated according
to inset in each
pane) bond-length ratios computed relative to the sums of covalent
radii for NX subset octahedral Fe(II) (top) and Fe(III) (bottom) complexes
with N/Cl (left), N/O (middle), and N/S (right) coordinating atoms.
Ratios of 0.95 and 1.05 are indicated by gray dotted lines. Only points
for which spin-state assignment is confident are shown, and triangle
down symbols indicate LS, whereas triangle up indicates HS. The total
number with each spin assignment is shown in the bottom right corner
of each pane. The Fe–N, Fe–X pair is computed from the
average of all bonds of that type in the complex. Three representative
HS Fe(II) complexes are shown at top and correspond to the only symbol
that is solid filled with a dark colored border in each representative
pane: N/Cl (left, CSD: POKNEJ), N/O (middle, CSD: DAQVEZ), N/S (right,
CSD: ZERFEK). Structures are shown as sticks with carbon in gray,
nitrogen in blue, hydrogen in white, chlorine in green, sulfur in
yellow, oxygen in red, and iron in brown.