Metal Ion Binding to Octakis(dimethylamino)porphyrazine: Core Coordination of Mn(III) and Peripheral Coordination of Pd(II)

The synthesis and X-ray structural characterization of
two manganese(III) porphyrazine (tetraazaporphyrin)
complexes are reported: 
[Mn(Et2dtc)ODMAPz] (1) and
[Mn(Cl)ODMAPz] (2) (Et2dtc =
diethyldithiocarbamato;
ODMAPz =
2,3,7,8,12,13,17,18-octakis(dimethylamino)porphyrazinato).
In both 1 and 2, the Mn(III) ion
sits
∼0.3 Å out of the plane of the pyrrolic nitrogen atoms toward the
axial ligand. The structural data reveal that
for both 1 and 2 the Mn(III) ions are
isolated from each other, simplifying the interpretation of the
magnetic
behavior of these compounds. Cyclic voltammetry shows that the
peripheral dimethylamino groups make these
metalloporphyrazines extremely electron-rich, with the
Mn(III)/Mn(II) couple at −1.3 V (versus
ferrocenium/ferrocene), shifted approximately 0.6−0.9 V more negative than those
of related manganese macrocycles.
Temperature-dependent magnetic susceptibility measurements show
that the ground state is S = 2 with axial
zero-field splitting, and |D| = 3.1−3.3
cm-1 for both 1 and 2.
These bulk magnetic measurements are compared
to the magnetic behavior of Mn(III) porphyrin-type complexes, as
well as recent direct resonance measurements
on 1 and 2 by high-field EPR spectroscopy.
The related metalloporphyrazine NiODMAPz, with an
internally
bound Ni(II) ion, coordinates 4 equiv of PdCl2 to the
peripheral dimethylamino sites to give
[Ni(ODMAPz)(PdCl2)4] (5). Compound
1 crystallizes in C2/c, with a
= 22.480(3) Å, b = 20.128(2) Å,
c = 19.423(3) Å, β =
102.97(1)°, V = 8564(2) Å3, and
Z = 8 (R1 = 0.074,
wR2 = 0.169). Compound 2
crystallizes in P1̄ with a =
10.216(6) Å, b = 13.426(8) Å, c =
15.683(14) Å, α = 114.59(5)°, β =
96.82(6)°, γ = 101.87(5)°, V =
1863(2)
Å3, and Z = 2 (R1 =
0.067, wR2 = 0.183).