The synthesis and characterization of the
trifluoromethanesulfonato derivatives of bis(dimethyl
phenylphosphonite)(tetrakis(p-methylphenyl)porphyrinato)ironIII,
1, and bis(diethyl
phenylphosphonite)(tetrakis(p-methylphenyl)porphyrinato)ironIII, 2, are reported:
[(PPh(OMe)2)2Fe(T(p-Me)PP)]CF3SO3,
1, and
[(PPh(OEt)2)2Fe(T(p-Me)PP)]CF3SO3, 2,
(T(p-Me)PP =
tetrakis(p-methylphenyl)porphyrinato). The
crystal structure of complexes 1
and 2 have been determined. Both X-ray structures show
that the porphyrinate rings are strongly ruffled. The
equatorial Fe−N bond distances average to 1.971 (6) Å for 1
and to 1.969 (7) Å for 2, which is a quite
short
distance for low-spin ironIII porphyrinate derivatives.
The 1H NMR isotropic shifts at 20 °C of the pyrrole
protons
of the two complexes, varied from −2 ppm for 2 to +3 ppm
for 1 rather than the expected −20 to −30
ppm,
based on previously studied bis-ligated complexes of low-spin ferric
porphyrins. The electron paramagnetic
resonance spectra of
[(PPh(OMe)2)2Fe(T(p-Me)PP)]CF3SO3,
1, and
[(PPh(OEt)2)2Fe(T(p-Me)PP)]CF3SO3,
2, in
solution are axial, with g
⊥ = 2.36 and
g
∥ = 1.87−1.91 at 4 K,
Σg
2 = 14.7. The Mössbauer spectra
of 1 and 2
at 70 K have isomer shifts of 0.35 and 0.37 mm/s and quadrupole
splittings of 1.23 and 1.66 mm/s, respectively.
All physical properties are consistent with a low-spin
ironIII with an unusual ground-state configuration
(d
xz
,d
yz
)4(d
xy
)1, as recently reported for
[(4-CN−Py)2Fe(TPP)]ClO4
Safo, (M. K.; Walker, F. A.; Raitsimring, A. M.; Walters,
W. P.; Dolata, D. P.; Debrunner P. G.; Scheidt, W. R. J. Am.
Chem. Soc.
1994, 116, 7760−7770).
Crystal data
for
[(PPh(OMe)2)2Fe(T(p-Me)PP)]CF3SO3,
1:
a = 16.611(3) Å, c =
20.722(4) Å, trigonal, space group P32,
V
= 4951(2) Å3, Z = 3. Crystal data
for
[(PPh(OEt)2)2Fe(T(p-Me)PP)]CF3SO3,
2:
a = 24.017(2) Å, b =
14.380(9)
Å, c = 18.702(4) Å, monoclinic, space group
P21/a, V = 6457(6)
Å3, Z = 4.
