Iron complexes of 5,10,15,20-tetraphenyl-21-oxaporphyrin

Article abstract of DOI:10.1021/ic025718p

The iron complexes of 5,10,15,20-tetraphenyl-21-oxaporphyrin (OTPP)H have been investigated. Insertion of iron-(II) followed by one-electron oxidation yielded a high-spin, six-coordinate (OTPP)Fe^IIICl₂ complex. The reduction of (OTPP)Fe^IICl₂ has been accomplished by means of moderate reducing reagents producing high-spin five-coordinate (OTPP)Fe^IICl. The molecular structure of (OTPP)Fe^IIICl₂ has been determined by X-ray diffraction. The iron(Ill) 21-oxaporphyrin skeleton is essentially planar. The furan ring coordinates in the η¹ fashion through the oxygen atom, which acquires trigonal geometry. The iron(III) apically coordinates two chloride ligands. Addition of potassium cyanide to a solution of (OTPP)Fe^IIICl₂ in methanol-d₄ results in its conversion to a six-coordinate, low-spin complex [OTPP)Fe^III(CN)₂] which is spontaneously reduced to [OTPP)Fe^II(CN)₂]^- by excess cyanide. The spectroscopic features of [OTPP)Fe^III(CN)₂] correspond to the common low-spin iron(III) porphyrin (d_xy)²(d_xzd_yz)³ electronic configuration. Titration of (OTPP)Fe^IIICl₂ or (OTPP)Fe^IICl with n-BuLi (toluene-d₈, 205 K) resulted in the formation of (OTPP)Fe^II(CH₂CH₂CH₂ CH₃). (OTPP)Fe^II(n-Bu) decomposes via homolytic cleavage of the iron-carbon bond to produce (OTPP)Fe¹. The EPR spectrum (toluene-d₈, 77 K) is consistent with a (d_xy)²(d_xz)² (d_yz)²(d_z²)¹ (d_x²-y²)⁰ ground electronic state of iron(I) oxaporphyrin (g₁ = 2.234, g₂ = 2.032, g₃ = 1.990). The ¹H NMR spectra of (OTPP)-Fe^IIICl₂, (OTPP)Fe^III(CN)₂, {[(OTPP)Fe^III)]₂O}²⁺, and (OTPP)Fe^IICl have been analyzed. There are considerable similarities in ¹H NMR properties within each iron(n) oxaporphyrin-iron(n) regular porphyrin or N-methylporphyrin pair (n = 2, 3). Contrary to this observation, the pattern of downfield positions of pyrrole resonances at 156.2, 126.5, 76.3 ppm and furan resonance at 161.4 ppm (273 K) detected for the two-electron reduction product of (OTPP)Fe^IIICl₂ is unprecedented in the group of iron(I) porphyrins.

Full text of DOI:10.1021/ic025718p

Inorg. Chem. 2002, 41, 5866−5873
Iron Complexes of 5,10,15,20-Tetraphenyl-21-oxaporphyrin
Miłosz Pawlicki and Lechosław Latos-Graz3yn´ski*
Department of Chemistry, UniVersity of Wrocław, 50 383 Wrocław, Poland
Received May 14, 2002
The iron complexes of 5,10,15,20-tetraphenyl-21-oxaporphyrin (OTPP)H have been investigated. Insertion of iron-
III
(II) followed by one-electron oxidation yielded a high-spin, six-coordinate (OTPP)Fe Cl2 complex. The reduction of
III
(OTPP)Fe Cl2 has been accomplished by means of moderate reducing reagents producing high-spin five-coordinate
II
III
(OTPP)Fe Cl. The molecular structure of (OTPP)Fe Cl2 has been determined by X-ray diffraction. The iron(III)
21-oxaporphyrin skeleton is essentially planar. The furan ring coordinates in the η1 fashion through the oxygen
atom, which acquires trigonal geometry. The iron(III) apically coordinates two chloride ligands. Addition of potassium
III
cyanide to a solution of (OTPP)Fe Cl2 in methanol-d4 results in its conversion to a six-coordinate, low-spin complex
III
II
[OTPP)Fe (CN)2] which is spontaneously reduced to [OTPP)Fe (CN)2]- by excess cyanide. The spectroscopic
features of [OTPP)Fe (CN)2] correspond to the common low-spin iron(III) porphyrin (dxy)2(d d )3 electronic
configuration. Titration of (OTPP)Fe Cl2 or (OTPP)Fe Cl with n-BuLi (toluene-d8, 205 K) resulted in the formation
of (OTPP)Fe (CH CH CH CH ). (OTPP)Fe (n-Bu) decomposes via homolytic cleavage of the iron−carbon bond to
III
xz yz
III
II
II
II
2
2
2
3
I
2
2
2
1
0
2
2
2
produce (OTPP)Fe. The EPR spectrum (toluene-d8, 77 K) is consistent with a (d ) (d ) (d ) (d ) (dx -y ) ground
xy
xz
yz
z
electronic state of iron(I) oxaporphyrin (g1 ) 2.234, g2 ) 2.032, g3 ) 1.990). The 1H NMR spectra of (OTPP)-
Fe Cl2, (OTPP)Fe (CN)2, {[(OTPP)Fe )]2O}2+, and (OTPP)Fe Cl have been analyzed. There are considerable
similarities in 1H NMR properties within each iron(n) oxaporphyrin−iron(n) regular porphyrin or N-methylporphyrin
pair (n ) 2, 3). Contrary to this observation, the pattern of downfield positions of pyrrole resonances at 156.2,
126.5, 76.3 ppm and furan resonance at 161.4 ppm (273 K) detected for the two-electron reduction product of
III
III
III
II
III
(OTPP)Fe Cl2 is unprecedented in the group of iron(I) porphyrins.
Introduction
metal and the complexing porphyrin or heteroporphyrin.1,2
Only in 21-oxaporphyrin, 21,23-dioxaporphyrin, and 21-
oxacorrole is the size of the coordinating center comparable
with that of regular porphyrins, because the atomic radii of
nitrogen and oxygen are similar.5-7 In these terms, the
situation is radically different for 21-thiaporphyrin or 21-
selenaporphyrin as reflected by remarkable differences in the
observed 21-oxaporphyrin and 21-thiaporphyrin or 21-
selenaporphyrin coordination modes.2,6,8,9
Core-modified porphyrins are formally related to regular
porphyrins by a replacement of a NH fragment by a
heteroatom typically from group 16 of the periodic table.1-4
In the macrocyclic environment, a heteroatom can function
as a donor toward a variety of metal ions, offering an insight
into coordination properties of furan, thiophene, or seleno-
phene, respectively.2 The presence of the heavier heteroatoms
shrinks the coordination core of heteroporphyrin in com-
parison to regular porphyrins. Matching the cavity size of a
macrocycle to the ionic radius of a metal is of prime
importance when considering complex formation between a
The coordination chemistry of heteroporphyrins has been
explored for a number of metal ions: for 21-oxaporphyrin,
Ni(II),6 Ni(I),6 Zn(II),10 Co(II),10 Mn(II),10 Cu(II);11 for 21-
(5) Latos-Graz˘yn´ski, L.; Pacholska, E.; Chmielewski, P.; Olmstead, M.
M.; Balch, A. L. Angew. Chem., Int. Ed. Engl. 1995, 34, 2252.
(6) Chmielewski, P. J.; Latos-Graz˘yn´ski, L.; Olmstead, M. M.; Balch, A.
L. Chem. Eur. J. 1997, 3, 268.
(7) Sridevi, B.; Narayanan S. J.; Chandrashekar, T. K. Chem. Eur. J. 2000,
6, 2554.
* To whom correspondence should be addressed. E-mail: LLG@
wchuwr.chem.uni.wroc.pl.
(1) Latos-Graz˘yn´ski, L.; Chmielewski, P. J. New J. Chem. 1997, 21, 691.
(2) Latos-Graz˘yn´ski, L. Core Modified Heteroanalogues of Porphyrins
and Metalloporphyrins. In The Porphyrin Handbook; Kadish, K. M.,
Smith, K. M., Guilard, R., Eds.; Academic Press: New York, 2000;
Vol. 2, p 361.
(8) Latos-Graz˘yn´ski; L.; Lisowski, J.; Olmstead, M. M.; Balch, A. L.
Inorg. Chem. 1989, 28, 1183.
(3) Vogel, E. Pure Appl. Chem. 1993, 66, 143.
(4) Vogel, E. J. Heterocycl. Chem. 1996, 33, 1461.
(9) Latos-Graz˘yn´ski, L.; Pacholska, E.; Chmielewski, P. J.; Olmstead, M.
M.; Balch, A. L. Inorg. Chem. 1996, 35, 566.
5866 Inorganic Chemistry, Vol. 41, No. 22, 2002
10.1021/ic025718p CCC: $22.00 © 2002 American Chemical Society
Published on Web 10/02/2002

5,10,15,20-Tetraphenyl-21-oxaporphyrin Complexes
thiaporphyrin, Li(I),12 Cu(II),13,14 Ni(II),8 Ni(I),15 Fe(II),8 Pd-
(II),16 Rh(III);17 for 21-selenaporphyrin, Ni(II);9 for 21,23-
dioxaporphyrin, Ni(II);6,18 for 21-oxa-23-thiaporphyrin, Cu(II);11
and for 21,23-dithiaporphyrin, Ru(II).19 This laboratory has
systematically examined the coordination chemistry of nickel
heteroporphyrins.1,2,6,8,15,17 It was determined that heteropor-
phyrins stabilize the uncommon nickel(I).6,15 Once the nickel-
(II) ion was located in the heteroporphyrin macrocycle, the
extremely rare high-spin organonickel(II) complexes could
be trapped and identified.20-22 Organometallic chemistry of
nickel(II) and stabilization of nickel(I) attracted much
attention in light of their biochemical implications. Suggested
participation of analogous species in the mechanisms of
reactions of methyl-S-coenzyme-M reductase provided some
motivation for the effort in this direction.23,24
Chart 1
iron N-alkyl porphyrins,27-32 here we report on the structure
and spectroscopic properties of iron(n) 21-oxaporphyrins.
1H NMR spectroscopy was shown to be a definitive
method for detecting and characterizing iron porphyrins33
and iron(n) N-substituted porphyrins26-29,31-33 at different
coordination/oxidation states. Consequently, we have ex-
plored the relation between the coordination geometry and
isotropic shifts in a series of iron(n) 21-oxaporphyrins.
There has been relative little attention given to iron
heteroporphyrins despite the extensive search for suitable
porphyrins and metalloporphyrins to act as biomimetic
models of the multiple fundamental biochemical roles played
by iron protoporphyrin IX.25 In the single case studied, it
was found that high-spin iron(II) 21-thiaporphyrin is a five-
coordinate complex where the thiophene ring coordinates in
the side-on fashion.8
Results and Discussion
Formation and Characterization of Iron(III) Com-
plexes. Insertion of iron into 5,10,15,20-tetraphenyl-21-oxa-
porphyrin (OTPP)H (Chart 1) has been readily achieved by
addition of a methanol solution of iron(II) chloride hydrate
to a chloroform solution of the ligand. The presence of
methanol is essential for metalation and facilitates the
reaction by producing soluble forms of iron(II). The reaction
results in the formation of a six-coordinate (OTPP)FeIIICl2
complex. Presumably, the originally formed (OTPP)FeIICl
is oxidized in the presence of dioxygen after the insertion
step has occurred. (OTPP)FeIIICl2 is stable as a solid and in
solution. It has good solubility in chloroform, methylene
chloride, and toluene.
Because of the size of the coordinating core and the
feasible in-plane coordination of the furan ring, the 21-
oxaporphyrin provides the most suitable environment to
explore iron chemistry. In comparison to regular iron
porphyrins, the properties of iron 21-oxaporphyrin are
expected to reflect the influence of the decreased anionic
charge and the replacement of the nitrogen by the oxygen
atom. Actually, the charge of the ligand and the size of the
coordination resemble those of N-alkylporphyrins.26 Thus,
particularly in light of the rich and interesting chemistry of
Moderate reducing reagents are sufficient to carry out one-
electron reduction of (OTPP)FeIIICl2. Reduction in chloro-
form by aqueous sodium dithionite or zinc amalgam produces
iron(II) derivatives. To avoid any complication with axial
ligation, zinc amalgam has been used for the preparative
reduction according to the reaction:
(10) Broadhurst, M. J.; Grigg, R.; Johnson, A. W. J. Chem. Soc. C 1971,
3681.
(11) Sridevi, B.; Narayanan, S. J.; Srinivasan, A.; Chandrashekar, T. K.;
Subramanian, J. J. Chem. Soc., Dalton Trans. 1998, 1979.
(12) Gebauer, A.; Schmidt, J. A. R.; Arnold, J. Inorg. Chem. 2000, 39
3424.
(13) Latos-Graz˘yn´ski, L.; Lisowski, J.; Olmstead, M. M.; Balch, A. L. J.
Am. Chem. Soc. 1987, 109, 4428.
(14) Lisowski, J.; Grzeszczuk, M.; Latos-Graz˘yn´ski, L. Inorg. Chim. Acta
1989, 161, 153.
(OTPP)FeIIICl2 + e- f (OTPP)FeIICl + Cl-
(1)
(15) Chmielewski, P. J.; Grzeszczuk, M.; Latos-Graz˘yn´ski, L.; Lisowski,
J. Inorg. Chem. 1989, 28, 3546.
The chemical reduction is reversible. Addition of oxidizing
reagents (Br2, I2) regenerates the iron(III) complexes. The
progress of the reaction was conveniently followed by
(16) Latos-Graz˘yn´ski, L.; Lisowski, J.; Chmielewski, P. J.; Grzeszczuk,
M.; Olmstead, M. M.; Balch, A. L. Inorg. Chem. 1994, 33, 192.
(17) Latos-Graz˘yn´ski, L.; Lisowski, J.; Olmstead, M. M.; Balch, A. L. Inorg.
Chem. 1989, 28, 3328.
(18) Gross, Z.; Saltsman, I.; Pandian, R. P.; Barzilay, C. Tetrahedron Lett
1997, 38, 2383.
(19) Hung, C.-H.; Ou, C.-K.; Lee, G.-H.; Peng, S.-M. Inorg. Chem. 2001,
40, 6854.
(20) Chmielewski, P. J.; Latos-Graz˘yn´ski, L. Inorg. Chem. 1992, 31, 5231.
(21) Pacholska, E.; Chmielewski, J. P.; Latos-Graz˘yn´ski, L. Inorg. Chim.
Acta 1998, 273, 184.
(27) Balch; A. L.; Chang; Y.-W.; La Mar; G. N.; Latos-Graz˘yn´ski, L.;
Renner, M. W. Inorg. Chem. 1985, 24, 1437.
(28) Balch; A. L.; La Mar; G. N.; Latos-Graz˘yn´ski, L.; Renner, M. W.
Inorg. Chem. 1985, 24, 2432.
(29) Wysłouch, A.; Latos-Graz˘yn´ski, L.; Grzeszczuk, M.; Drabent, K.;
Bartczak, T. Chem. Commun. 1988, 1377.
(22) Chmielewski, P. J.; Latos-Graz˘yn´ski, L. Inorg. Chem. 1998, 37, 4179.
(23) Jaun, B. In Metal Ions in Biological Systems; Sigel, H., Sigel, A.,
Eds.; Marcel Dekker: New York, 1993; Vol. 29, p 287.
(24) Ermler, U.; Grabarse, W.; Shima, S.; Goubeaud, M.; Thauer, R. K.
Science 1997, 278, 1457.
(25) Biochemistry and Binding. In The Porphyrin Handbook; Kadish, K.
M., Smith, K. M., Guilard, R., Eds.; Academic Press: New York,
2000; Vol. 4.
(30) Bartczak, T.; Latos-Graz˘yn´ski, L.; Wysłouch A. Inorg. Chim. Acta
1990, 171, 205.
(31) Balch, A. L. Cornman, C. R.; Latos-Graz˘yn´ski, L.; Olmstead, M. M.
J. Am. Chem. Soc. 1990, 112, 7552.
(32) Balch, A. L.; Cornman, C. R.; Latos-Graz˘yn´ski, L.; Renner, M. W. J.
Am. Chem. Soc 1992, 114, 2230.
(33) Walker, F. A. Proton NMR Spectroscopy of Paramagnetic Metal-
loporphyrins. In The Porphyrin Handbook; Kadish, K. M., Smith, K.
M., Guilard, R., Eds.; Academic Press: New York, 2000; Vol. 5, p
81.
(26) Lavallee, D. K. The Chemistry and Biochemistry of N-substituted
Porphyrins; VCH: New York, 1987.
Inorganic Chemistry, Vol. 41, No. 22, 2002 5867

Pawlicki and Latos-Graz3yn´ski
Figure 1. UV-vis spectra of iron(n) 21-oxaporphyrin complexes in
dichloromethane: (OTPP)FeIIICl2 (s), (OTPP)FeIICl (---), and (OTPP)-
FeI(toluene) (‚‚‚).
electronic spectroscopy. The electronic absorption spectra
of (OTPP)FeIIICl2 and (OTPP)FeIICl are shown in Figure 1.
Metalloporphyrin-like spectra are clearly present for both
complexes with a split Soret band and two (iron(III)) or three
(iron(II)) broad Q-bands, respectively.
The cyclic voltammetry experiment has been carried out.
The half-wave potentials for the two one-electron reductions
of (OTPP)FeIIICl2 equal (1) 0.595 and (2) -0.895 (in V vs
Ag/AgCl, CH2Cl2 solution, TBAP). Consequently, the first
reductions can be assigned to the FeIII/FeII metal-centered
processes. Cyclic voltammetry revealed that there is signifi-
cant stabilization of the divalent oxidation state in the iron
21-oxaporphyrin complex in comparison to regular iron
porphyrins. For instance, for (TPP)FeIIICl, the reduction
potential for Fe(III) to Fe(II) equals -0.121 V (DMF vs Ag/
AgCl).34 Interestingly, the analogous reduction potential for
(NCH3TPP)FeIIICl+ equals 0.51 V (vs Ag/AgCl).35 The
second half-wave potential may be accounted for the (OTPP)-
FeII/(OTPP)FeI couple or, alternatively, for (OTPP•-)FeII/
(OTPP)FeII.
Figure 2. Perspective drawing (with 50% probability ellipsoids) of
(OTPP)FeIIICl2 showing one of the molecular orientations. The lower view
in which aryl groups are omitted emphasizes the planarity of the macrocycle.
Crystal Structure of (OTPP)FeIIICl2. The structure has
been studied by X-ray diffraction. The perspective views of
the complex are shown in Figure 2.
The structure of (OTPP)FeIIICl2 displays disorder in the
location of furan oxygen and pyrrolic nitrogens. The structure
has been refined to give 25% occupancy with oxygen and
75% occupancy with nitrogen at each five-membered ring.
The iron(III) 21-oxaporphyrin skeleton is essentially planar.
Thus, the iron(III) is coplanar with the furan ring. It implies
that the furan ring is planar and coordinates in the η1 fashion
through the oxygen atom which acquires trigonal geometry.
The FeIII-Cl(1) (2.302(1) Å) and FeIII-Cl(2) (2.302(1) Å)
distances are among the longest found for high-spin iron-
(III) porphyrins (e.g., in (TPP)FeIIICl, FeIII-Cl 2.218(6) Å).36
This is a considerable lengthening of the FeIII-Cl bonds
which can readily be ascribed to the mutual trans interaction
of axial chloride ligands. A similar phenomenon was
previously observed in the (â-PPh3-TPP)FeIIICl2 structure
(FeIII-Cl, 2.429(3) and 2.348(3) Å).37
Figure 3. 1H NMR spectra (298 K, CDCl3) of (A) (OTPP)FeIIICl2 and
(B) (OTPP)FeIICl. Insets show spectra for (OTPP-d6)FeIIICl2 and (OTPP-
d6)FeIICl, respectively. The pyrrole, furan, and ortho, meta, and para
resonances are labeled pyrr, f, o, m, p, respectively.
1H NMR Studies of High-Spin Iron(II) and Iron(III)
1
21-Oxaporphyrins. The H NMR spectra of the paramag-
netic (OTPP)FeIIICl2 and (OTPP)FeIICl are shown at Figure
3. The spectral parameters for these and other relevant
compounds are gathered in Table 1.
The spectroscopic data for iron 21-oxaporphyrins have
been analyzed through the consideration of their effective
symmetry in solution. (OTPP)FeIIICl2 appears to have the
effective C2V geometry with one of the mirror planes passing
through the iron, chloride, and the furan oxygen. In this case,
there are three distinct pyrrole protons and one furan proton.
Their ortho and meta positions are pairwise equivalent
because of the mirror symmetry with respect to the porphyrin
(34) Donohoe, R. J.; Atamian, M.; Bocian, D. F. J. Am. Chem. Soc. 1987,
109, 5593.
(35) Anderson, O. P.; Kopelove, A. B.; Lavallee, D. Inorg. Chem. 1980,
19, 2101
(36) Hoard, J. L.; Cohen, G. H.; Glick, M. D. J. Am. Chem. Soc. 1967, 89,
1992
(37) Małek, A.; Latos-Graz˘yn´ski, L.; Bartczak, T.; Za¸dło, A. Inorg. Chem.
1991, 30, 3222.
5868 Inorganic Chemistry, Vol. 41, No. 22, 2002

5,10,15,20-Tetraphenyl-21-oxaporphyrin Complexes
Table 1. Chemical Shifts of Iron(n) Oxaporphyrinsa
furan
pyrrole
meso-phenyl
[(OTPP)FeIIICl2]b
[(OTPP)FeIICl]b
47.7
33.2
66.3
39.3
67.9
29.5
86.2
-6.4
10.9(o), 11.5(m), 9.1(o), 9.6(m), 8.7(p), 7.8(p)
13.1(o), 9.7(o), 9.3(o), 9.2(m),
8.6(p), 8.2(m), 7.8(m), 7.4(p), 6.9(o), 6.5(m),
6.8(p), 6.5(m), 6.2(p), 6.1(m), 5.9(o), 4.6(o),
7.99(o), 7.93(o), 7.66(m,p), 7.55(m), 2.64(pCH3)
8.04(2xo), 7.78(o), 7.5(o),7.41(m), 7.31 (2xp,m)7.21(m),
22(o or m),21.3(o or m), 12.6(p), 12.4(p)
[(OTPP)FeIII(CN)2]b
[(ODPDTP)FeII(CN)2]- b
[(OTPP)FeIIn-Bu]c,e
[(OTPP)Fe]d,e
-5.4
-16.2
-24.6
8.35(d)
7.58(d)
129.5
-40.5
8.56(s)
8.40(d)
7.65(d)
156.2
8.06(s)
7.04(s)
76.3
7.75(s)
161.4
a Unless otherwise indicated, all compounds measured in chloroform-d. b 295 K. c 215 K (R-CH2, -5.96 ppm; â-CH2, -1.64 ppm; γ-CH2, -0.36 ppm;
δ-CH3, 0.12 ppm). d -273 K. e Measured in toluene-d8.
plane. However, for (OTPP)FeIICl, the symmetry lowers to
Cs, and two ortho and two meta positions on each phenyl
ring will be distinguishable by 1H NMR unless the rotation
around the Cmeso-CR bond is sufficiently fast.33
Apart from these geometrical considerations, the resonance
assignments, which are given above each peak in Figure 3,
have been made on the basis of relative intensities, line
widths, and site specific deuteration. To distinguish the
pyrrole and furan resonances, the 1H NMR spectra of pyrrole-
Figure 4. 1H NMR spectrum of (OTPP)FeIII(CN)2 (298 K, CDCl3).
deuterated (OTPP-d6)FeIIICl2 and (OTPP-d6)FeIICl have been
Labeling follows that in Figure 3. Inset shows spectrum for (OTPP-d6)-
FeIII(CN)2.
obtained and are shown in insets of Figure 3, respectively.
The three pyrrole resonances of (OTPP)FeIIICl2 are in the
90-60 ppm region (298 K) which is typical for high-spin
iron(III) tetraarylporphyrins33,38 and N-methylporphyrins.28,31
The furan resonance is located at 47.7 ppm.
ization in σ as well as both filled and vacant π molecular
orbitals corresponding to 3π and 4π* orbitals of the regular
porphyrin.27,39,40
1H NMR Characterization of Low-Spin Iron(III) Por-
phyrins. Addition of potassium cyanide in excess to a
solution of (OTPP)FeIIICl2 in methanol-d4 results in its
conversion to six-coordinate low-spin complex [(OTPP)FeIII-
(CN)2]. The representative 1H NMR spectrum for [(OTPP)-
FeIII(CN)2] is shown in Figure 4.
Curie plots for pyrrole and furan resonances of (OTPP)-
FeIIICl2 and (OTPP)FeIICl (See Supporting Information) show
linear behaviors, but the extrapolated intercepts are fairly
far from the diamagnetic positions of [(OTPP)FeII(CN)2]-
(Table 1). Significantly, the deviations from the Curie law
differ for each pyrrolic position.
One-electron reduction of (OTPP)FeIIICl2 to (OTPP)FeII-
Cl resulted in characteristic spectroscopic changes. In this
case, the furan resonance has been unambiguously identified
The characteristic set of three upfield shifted pyrrole and
one furan resonance of [(OTPP)FeIII(CN)2] has been detected.
These resonances are accompanied by a group of upfield
shifted ortho, meta, and para meso-phenyl proton resonances.
As usual for low-spin iron(III) porphyrins, formed by
coordination of two cyanide ligands, this compound dem-
onstrates very narrow paramagnetically shifted resonances
due to the optimal relaxation properties.33 The primary
assignment could be made on the basis of the position of
resonances, their intensities, deuteration, and the COSY map.
The paramagnetic shifts of [(OTPP)FeIII(CN)2] vary linearly
with T-1 (see Supporting Information), but the extrapolated
lines do not pass through the positions expected for the
diamagnetic references.33,37
1
at 33.2 ppm because it is present in the H NMR spectrum
of (OTPP-d6)FeIICl where the ligand is deuterated in all
â-pyrrole positions. (Figure 3, trace B; Table 1). Two pyrrole
resonances are shifted downfield, and one is shifted upfield.
The upfield position of the regular pyrrole resonance was
previously found for iron(II) N-methylporphyrin (N-CH3-
TPP)FeIICl and iron(II) 21-thiaporphyrin (STPP)FeIICl.8,27
The paramagnetic shifts of the high-spin iron(III) and iron-
(II) 21-oxaporphyrins can be explained in terms typically
applied to regular iron porphyrins and iron N-substituted
porphyrins. In the case of a high-spin iron(III) center,
1
2
1
1
2
Under anaerobic conditions, the cyanide anion acts as a
one-electron reducing reagent to produce the diamagnetic
2
2
(dxy) (dxzdyz) (dz ) (dx -y ) , both σ and π delocalization routes
of spin density can operate. The domination of the σ route
results in the downfield shifts of pyrrole resonances as seen
for (OTPP)FeIIICl2.31,33,38,39
1
[(OTPP)FeII(CN)2]- identified here by means of H NMR
(Table 1). Addition of dioxygen to the sample results in a
slow formation of the µ-oxo diiron(III) derivative {[(OTPP)-
FeIII]2O}2+. Its identity is confirmed by a set of four new
resonances arising at 16-12 ppm, that is, in the region typical
for strongly antiferromagnetically coupled µ-oxo di-iron
The observed pyrrole and furan hyperfine shifts of
(OTPP)FeIICl are consistent with the high-spin iron(II)
1
1
1
1
2
(dxy)2(dxz ) (dyz) (dz ) (dx -y ) ground electronic state. The
pattern for the contact shift arises from the cancellation of
effects of unpaired spin density resulting from spin delocal-
2
2
(39) La Mar, G.; Walker, F. A. In The Porphyrins; Dolphin, E. Ed.;
Academic Press: New York, 1979; Vol. IVB, p 57.
(40) Lisowski, J.; Latos-Graz˘yn´ski, L.; Szterenberg, L. Inorg. Chem. 1992,
31, 1933.
(38) Wojaczyn´ski, J.; Latos-Graz˘yn´ski, L.; Hrycyk, H.; Pacholska, E.;
Rachlewicz, K.; Szterenberg, L. Inorg. Chem. 1996, 35, 6861.
Inorganic Chemistry, Vol. 41, No. 22, 2002 5869

Pawlicki and Latos-Graz3yn´ski
Integration of the â-H and the axial ligand resonances
indicates that one axial ligand is present in the iron(II)
complexes. These spectral characteristics confirm that the
iron(II) 21-oxaporphyrin alkyl complex is similar to known
(TPP)FeII(n-propyl), (TPP)FeII(ethyl), and (Pc)FeII(alkyl)
complexes.43,44 Some upfield relocation of the pyrrole and
furan resonances with respect to diamagnetic [(OTPP)FeII-
(CN)2]- results presumably from a rapid electron exchange
with a residual low-spin [(OTPP)FeIII(n-Bu)]-. Alternatively,
some admixture of the paramagnetic configuration to the
ground electronic state of (OTPP)FeII(n-Bu) can be consid-
ered.
The formation of (OTPP)FeII(n-Bu) has been accounted
for by a two-step process according to the following
equations:
(OTPP)FeIIICl2 + n-BuLi f
{(OTPP)FeIIICl(n-Bu)} + LiCl (2)
Figure 5. Plot of the chemical shift versus 1/T for {[(OTPP)FeIII)]2O}2+
.
Inset presents the pyrrolic fragment of the 1H NMR spectrum (298 K,
CDCl3). The solid lines are for illustrative purpose only.
{(OTPP)FeIIICl(n-Bu)} f (OTPP)FeIICl + Bu• (3)
(OTPP)FeIICl + n-BuLi f (OTPP)FeII(n-Bu) + LiCl (4)
Alkyllithium, aryllithium, or Grignard reagents are known
to act as one-electron reducing reagents.45-49 The reduction
has been also demonstrated in several attempts to generate
metalloporphyrins with metal-carbon bonds.48,49 To clarify
the point that the formation of (OTPP)FeII(n-Bu) from
(OTPP)FeIIICl2 has been preceded by one-electron reduction
step, we have demonstrated that this species can be obtained
by an independent route. Thus, the sample of (OTPP)FeII-
Cl, obtained by reduction of (OTPP)FeIIICl2 with zinc
amalgam, was dissolved in toluene-d8 and titrated with
n-BuLi (205 K) to yield (OTPP)FeII(n-Bu). The observation
of the solution behavior of (OTPP)FeII(n-Bu) revealed that
this complex is thermally stable at 205 K. Warming of
(OTPP)FeII(n-Bu) in toluene-d8 resulted in its complete
decomposition at 250 K after 45 min. The process yielded a
Figure 6. 1H NMR spectrum of (OTPP)FeII(n-butyl) (215 K, toluene-d8).
Labeling follows that in Figure 3. The alkyl ligand resonances are labeled
R, â, δ, γ. Inset shows the spin-spin splitting of the n-butyl chain.
porphyrin complexes.29,33,39 An increase of the pyrrole and
furan resonance shifts on warming reflects the anti-Curie
behavior expected for such an electronic structure (Figure
5).41 The reduction of (OTPP)FeIII(CN)2 by cyanide has the
precedence in the reactivity of regular iron(III) porphyrins.42
Reaction with Carbanions. Treatment of (OTPP)FeIII-
Cl2 in toluene-d8 solution with n-butyllithium in hexane
solution at 205 K results in the conversion to (OTPP)-
FeII(CH2CH2CH2CH3) (Figure 6).
1
new compound detected by H NMR spectroscopy (Figure
7).
The formation of the new species can be accounted for
by a homolytic cleavage of the iron-carbon bond according
to the following reaction:
(OTPP)FeII(n-Bu) f (OTPP)FeI + Bu•
(5)
Notably, (OTPP)FeI has been generated using the inde-
pendent routes. Thus, the reduction of (OTPP)FeIICl in
toluene-d8 with NaBH4 in THF gives (OTPP)FeI. Treatment
The four resonances expected for a coordinated n-butyl
group are present with the upfield ring current shifts which
are similar to those of diamagnetic metalloporphyrin bearing
axial alkyl ligands (R-CH2, -5.96; â-CH2, -1.64; γ-CH2,
-0.35; δ-CH3, 0.12 ppm). It should be noticed that the spin-
spin splittings expected for such a n-butyl ligand are clearly
resolved and the scalar connectivity scheme was confirmed
by the COSY experiment. The pyrrole and furan resonances
are located at 7.75 (H2,3); 7.65, 7.58 (H7,H8), 7.04 (H12,-
13) ppm, respectively.
(43) Balch, A. L.; Cornman, C. R.; Safari, N.; Latos-Graz˘yn´ski, L.
Organometallics 1990, 9, 2420.
(44) Tahiri, M.; Doppelt, P.; Fischer, J. Weiss, R. Inorg. Chem. 1988, 27,
2897.
(45) Cloutour, C.; Debaig-Valade, C.; Gacherieu, C.; Pommier, J.-C. J.
Organomet. Chem. 1984, 269, 239.
(46) Stasˇko, A.; Tka´cˇ, A.; Mal´ık, L.; Adamcˇ´ık, V. J. Organomet. Chem.
1975, 92, 261.
(47) Kane, K. M.; Lemke, F. R.; Petersen, J. L. Inorg. Chem. 1997, 36,
1354.
(48) Chmielewski, P. J.; Latos-Graz˘yn´ski, L. Inorg. Chem. 2000, 39, 5639.
(49) Balch, A. L.; Hart, R. H.; Latos-Graz˘yn´ski, L.; Traylor, T. G. J. Am.
Chem. Soc. 1990, 112, 7382.
(41) Boersma, A. D.; Goff, H. M. Inorg. Chem. 1984, 23, 1617.
(42) La Mar, G. N.; Del Gaudio, J. AdV. Chem. Ser. 1977, 162, 207.
5870 Inorganic Chemistry, Vol. 41, No. 22, 2002

5,10,15,20-Tetraphenyl-21-oxaporphyrin Complexes
Figure 7. 1H NMR spectrum of (OTPP)FeI (273 K, toluene-d8). Labeling
follows that in Figure 3. Inset shows spectrum for (OTPP-d6)FeI.
Figure 8. Curie plot (chemical shifts versus 1/T) for pyrrole and furan
resonances of (OTPP)FeI (toluene-d8). The solid lines are for illustrative
purposes only.
of (OTPP)FeIIICl2 with 2 equiv of PhMgBr yields (OTPP)-
FeI directly and cleanly at 205 K. Generally, reactions of
(OTPP)FeIIICl2 with carbanions (toluene-d8, 205 K) result
in a significantly different 1H NMR picture than that
determined for the analogous experiment with the use of
(TPP)FeIIICl and alkyl Grignard reagent or alkylithium
reagents where low-spin (TPP)FeIII(alkyl) or (TTP)FeIII(aryl)
or intermediate-spin (TPP)FeII was detected.33,49,50 Typically,
the reduction process of regular iron(III) porphyrins with
alkyl reagents stops at the iron(II) oxidation level.
As the identical product can be generated using different
reducing reagents, one unambiguously concludes that the
reaction product does not contain any apically bound aryl
or alkyl ligand. (OTPP)FeI is thermally stable in the 193-
272 K temperature range. Addition of dioxygen results in
the formation of (OTPP)FeIICl or (OTPP)FeIIBr as both
anions are present in the reaction mixture, allowing us to
conclude that the 21-oxaporphyrin ring remained intact in
the reaction. Despite the apparent differences in oxidation
Figure 9. EPR spectrum (X-band, toluene-d8, 77 K). The signal of the
residual radical is marked with an asterisk. Conditions: microwave
frequency ν ) 9.5750 GHz, microwave power 20 mW, modulation
amplitude 4.88 G, modulation frequency 100 kHz.
1
states, the H NMR spectrum of (OTPP)FeI bears some
features of high-spin (OTPP)FeIIICl2. Namely, the pyrrole
and furan resonances are shifted strongly downfield. Actually,
the shift values found for (OTPP)FeI are significantly higher
than those determined for (OTPP)FeIIICl2 at the same
temperature. Noticeably, the furan resonance, which demon-
strated the smallest shift for high-spin iron(III) species,
presents the largest one in the case of (OTPP)FeI. Two sides
of the 21-oxaporpyrin remain equivalent as a single reso-
nance has been detected for each meso-phenyl ring. The plots
of the temperature dependence of chemical shifts demonstrate
pronounced deviation from the Curie behavior (Figure 8).
While the spectroscopic properties of the newly detected
intermediate are consistent with the (OTPP)FeI stoichiometry,
the oxidation states of the iron and the 21-oxaporphyrin
ligand remain to be analyzed. Two alternative electronic
structures can be considered in analogy to two-electron
reduction products of iron(III) regular porphyrins.33,34,51-55
They are differentiated by localization of an added electron
leading either to iron(I) 21-oxaporphyrin or iron(II) 21-
oxaporphyrin π anion radical complexes, that is, (OTPP)FeI
or (OTPP•-)FeII, respectively. The EPR spectroscopy brings
a valuable insight into the electronic structure of (OTPP)FeI
at 77 K. The relevant EPR spectrum of (OTPP)FeI as frozen
toluene-d8 solution is shown in Figure 9. The species has
been prepared in the 5 mm NMR tube by addition of the
PhMgBr to (OTPP)FeIIICl2 at 205 K. The composition of
1
the solution has been confirmed by H NMR spectroscopy
before and after the EPR measurements. The species reveals
the remarkable anisotropy of the g tensor g1 ) 2.234, g2 )
2
2
2
1
0
2
2
2
2.032, g3 ) 1.990. This indicates a (dxy) (dxz) (dyz) (dz ) (dx -y
)
electronic state for the reduction product as detected at 77
K. The analogous EPR parameters have been reported for
other low-spin d7 complexes including iron(I) porphyrins.39,56
Electronic Structure of (OTPP)Fe: 1H NMR Studies.
1H NMR spectra of the two-electron reduced iron(III)
porphyrins are diagnostic for determination of a ground
electronic state. Depending on iron porphyrin substitution,
(50) Li, Z.; Goff, H. M. Inorg. Chem. 1992, 31, 1547.
(51) Reed, C. A. AdV. Chem. Ser. 1981, 201, 333.
(52) Mashiko, T.; Reed, C. A.; Haller, K. J.; Scheidt, W. R. Inorg. Chem.
1984, 23, 3192.
(53) Sano, S.; Suguira, Y.; Maeda, Y.; Ogawa, S. Morishima, I. J. Am.
Chem. Soc. 1981, 103, 2888.
(54) Hickman, D. L.; Shirazi, G.; Goff, H. M. Inorg. Chem. 1985, 24, 563.
(55) Yamaguchi, K.; Morishima, I. Inorg. Chem. 1992, 31, 3216.
(56) Kadish, K. M.; Van Caemelbecke, E.; D’Souza, F.; Lin, M.; Nurco,
D. J.; Medforth, C. J.; Forsyth, T. P.; Krattinger, B.; Smith, K. M.;
Fukuzumi, S.; Nakanishi, I.; Shelnut, J. A. Inorg. Chem. 1999, 38,
2188.
Inorganic Chemistry, Vol. 41, No. 22, 2002 5871

Pawlicki and Latos-Graz3yn´ski
the following possibilities have been realized (the significant
paramagnetic shifts are given for ca. 293 K in parentheses):
marked downfield shift of the pyrrole resonances was
observed.57,58
2
2
2
1
0
2
I
2
2
(a) low-spin iron(I) (dxy) (dxz ) (dyz) (dz ) (dx -y ) ([(TPP)Fe ]
â-H 29 ppm),54 (b) resonance structures between two low-
spin canonic forms (P•-)FeII T PFeI (e.g., iron porphyrin
containing electron-withdrawing substituents, [(CN)4TPP)Fe]-
pyrrole 11 ppm, o-H -0.8, m-H 13.7; p-H 3.4 ppm),55 (c)
Conclusions. This study broadens our understanding of
the coordination of iron in a porphyrin and porphyrin-like
environment. The essential similarities of iron porphyrin and
iron 21-oxaporphyrin complexes have been established. Both
form high-spin five-coordinate complexes, µ-oxo bridged
diiron(III) complexes, and low spin six-coordinate iron(III)
complexes with strong field ligands. In addition, σ-alkyliron-
(II) complexes have been detected in each case. Finally, two-
electron reduction of iron(III) porphyrin and iron(III) 21-
oxaporphyrin gave corresponding iron(I) compounds. There
2
2
1
1
1
2
2
2
high-spin ferrous iron(II) (dxy) (dxz) (dyz) (dz ) (dx -y ) coupled
to a π anion radical [d3-(5-NO2OEP)Fe]- R-CH2 60-40,
meso -58(2), -210(1)).55
Thus, (OTPP)FeI demonstrates spectroscopic features
never seen for iron tetraarylporphyrins obtained as a product
of two-electron reduction of iron(III) tetraarylporphyrins.
1
is a considerable analogy in the magnetic and H NMR
1
Importantly, the H NMR spectroscopic pattern measured
properties despite inherent lower symmetry of the 21-
oxaporphyrin within each iron(n) 21-oxaporphyrin-iron(n)
regular porphyrin pair. Actually, the best parallel can be
drawn between iron 21-oxaporphyrin and iron N-methylpor-
phyrin despite the difference in coordination mode of the
modified five-membered rings (N-methylated pyrrole, side-
on; furan, in-plane). Importantly, once the symmetry has been
lowered accompanied by a change of the macrocyclic charge
from -2 to -1, the stabilization of lower oxidation states
occurred. This is demonstrated for iron N-methylporphyrin
and iron 21-oxaporphyrin in comparison to iron porphyrins
as clearly seen at the iron(III)/iron(II) reduction level.
in the 203-273 K temperature range remains in a striking
contradiction to the EPR data (the frozen toluene-d8 glass,
77 K), which are unambiguously consistent with the
2
2
2
1
0
2
2
2
(dxy) (dxz) (dyz) (dz ) (dx -y ) ground electronic state. Defi-
nitely, raising the temperature resulted in the fundamental
change of the electronic structure.
As expected, the number of resonances for (OTPP)FeI
reflects the lower symmetry of 21-oxaporphyrin. Of particular
significance are the remarkable downfield shifts of the
pyrrole and furan resonances detected for (OTPP)FeI. The
pattern appears to result from a domination of the σ
delocalization pathways moderated by some contribution of
the π mechanism. Unequivocally, the unpaired electron is
Experimental Section
2
2
located on the dx -y orbital. In general, three electronic
structures or their combination are consistent with the
detected paramagnetic shifts: (a) high-spin iron(II) radical
Materials. 5,10,15,20-Tetraphenyl-21-oxaporphyrin (OTPP)H
and its derivative deuterated at â-pyrrole positions (OTPP-d6)H were
synthesized as described previously.6 C6H5MgBr, n-buthyllithium,
and sodium borohydride were purchased from Aldrich.
2
1
1
1
1
2
2
2
(dxy) (dxz) (dyz) (dz ) (dx -y ) coupled to 21-oxaporphyrin radi-
(OTPP)FeIIICl2. A solution of 200 mg (1 mmol) of iron(II)
chloride tetrahydrate in 5 mL of methanol was added to a solution
of 50 mg (0.07 mmol) of 5,10,15,20-tetraphenyl-21-oxaporphyrin
in 40 mL of chloroform. After 20 min, the solvent was removed
under reduced pressure. The solid residue was extracted with
dichloromethane, and the dichloromethane solution was separated
from the remaining solid by filtration. Recrystallization from
dichloromethane/hexane (50/50) produced 37 mg of (OTPP)FeIII-
Cl2 (yield 63%). UV-vis λ [nm] (log ꢀ) ) 412 (4.70), 435 (4.59),
568 (3.80), 597 (3.64). MS (ESI, m/z) 705.1241 (705.1348 calcd
for (C44H28N3OFeCl)+ , the most intensive peak). (OTPP-d6)FeIII-
Cl2 was obtained the same way using (OTPP-d6)H.
(OTPP)FeIICl. (OTPP)FeIIICl2 (20 mg) was dissolved in
chloroform and energetically stirred with zinc amalgam (2 h). The
reducing reagent was filtered off, and the solution of (OTPP)FeII-
Cl was taken to dryness under reduced pressure. Conversion into
the iron(II) compound proceeded quantitatively. Yield 19 mg. UV-
vis λ [nm] (log ꢀ) ) 426 (4.83), 442 (4.82), 546(3.83), 588 (3.73),
633 (3.39). MS (ESI, m/z) 670.1576 (670.1696 calcd for (C44H28-
N3OFe)+, the most intensive peak).
cal (S ) 3/2 or S ) 5/2), (b) high-spin iron(I) (dxy)2(dxz)2(dyz)1-
1
1
2
3
2
2
2
2
2
(dz ) (dx -y ) (S ) /2), (c) low-spin iron(I) (dxy) (dxz) (dyz) -
0
1
2
1
2
2
(dz ) (dx -y ) (S ) /2).
Actually, the first case has a precedent exemplified by d3-
[(5-NO2OEP)Fe]-.56 However, because of differences in
substitution, the direct spectroscopic comparison between
tetraaryl- and octaethylporphyrin derivatives is not possible.
One can expect that the large π spin density at the meso
position seen for [d3-(5-NO2OEP)Fe]- will be translated into
the relatively large isotropic shifts of meso-aryl protons with
sign alteration between meta and para (ortho) resonances.33
Accordingly, the large downfield shift of the R-methylene
protons can be translated into the large downfield shift from
replacing the â-H protons, presuming that the σ contribution
dominates the contact shift. The π delocalization effect is
less predictable. At this stage of discussion, we may conclude
that the contact shift of â-H results from the simultaneous
delocalization in σ as well as both filled and vacant molecular
orbitals related to the 3e(π) and 4e(π*) orbitals of the regular
porphyrin. Ultimately, the upfield π contribution due to
delocalization in the π orbitals may be overshadowed by the
strong downfield contribution of the σ mechanism.38
The high-spin d7 iron(I) allows both σ and π delocalization
routes as well. Such an electronic structure was never
X-ray Data Collection and Refinement. Crystals of (OTPP)-
FeIIICl2 were prepared by diffusion of hexane into the chloroform
solution contained in a thin tube.
Crystal data for (OTPP)FeIIICl2 are given in Table 2, together
with refinement details. The crystal was mounted on glass fiber
and then flash-frozen to 100 K (Oxford Cryosystem-Cryostream
1
characterized for iron(I) porphyrins. As an appropriate H
(57) Latos-Graz˘yn´ski, L. Inorg. Chem. 1985, 24, 1105.
NMR reference, one can suggest high-spin d7 cobalt(II)
complexes, (NCH3TPP)CoIICl and (STPP)CoIICl, where the
(58) Lisowski, J.; Latos-Graz˘yn´ski, L. Unpublished results, see ref 2, p
404.
5872 Inorganic Chemistry, Vol. 41, No. 22, 2002

5,10,15,20-Tetraphenyl-21-oxaporphyrin Complexes
Table 2. Crystal Data for (OTPP)FeIIICl2 with Refinement Details
primary orientation were refined with anisotropic displacement
parameters and isotropically in the molecule with secondary
orientation using instruction SAME; coordinates of the hydrogen
atoms were calculated using the geometry of molecules and were
refined as riding groups for all orientations of (OTPP)FeIIICl2. The
carbon-bonded hydrogen atoms were included in the calculated
positions and refined using a riding model.
Instrumentation. NMR spectra were recorded on a 500 MHz
Bruker Avance spectrometer equipped with a broadband inverse
gradient probehead. Proton data are referenced to the residual
solvent signal. EPR spectra were obtained with a Bruker ESP 300E
spectrometer. The magnetic field was calibrated with a proton
magnetometer and EPR standards.
(OTPP)FeIIICl2
formula
fw
C44H28N3OFeCl2
741.44
a,Å
b,Å
13.524(2)
13.524(2)
9.763(2)
1785.6(5)
2
1.379
tetragonal
I4/m
c,Å
V, Å3
Z,
D
calcd, g‚cm-3
cryst syst
space group
µ, mm-1
abs correction
Tmin
0.612
not applied
0.8621
Tmax
0.9584
Electrochemical measurements were performed in CH2Cl2 with
tetrabutylammonium perchlorate as supporting electrolyte. Cyclic
voltammograms were recorded for the potential scan rate ranging
from 0.02 to 0.5 V/s using the EA9C (MIM, Krako´w, Poland)
apparatus. The Pt-disk working electrode, Pt-wire auxiliary elec-
trode, and the Ag/AgCl reference electrode were utilized.
Sample Preparation. A sample of 3 mg of (OTPP)FeIIICl2 was
dissolved in 0.5 cm3 of oxygen-free toluene-d8 directly in an NMR
tube capped with a rubber septum cap. The sample was cooled to
193 K in the acetone slush bath, and the respective reagent (the
Grignard reagent, butyllithium) was titrated into the NMR tube
using a microsyringe. The sample was shaken vigorously and then
T, K
θ range
hkl range
100(2)
3.96 e θ e 28.55
-17 e h e 17
-17 e k e 17
-13 e l e 3
1133
1056
72/0
1.074
0.0801
reflns measured
reflns unique, I > 2σ(I)
params/restraints
S
R1a
wR2a
0.1912
2
2
2
a R1 ) ∑||Fo - Fc||/∑|Fo|, wR2 ) [∑[w(Fo - Fc )2/∑[w(Fo )2]]1/2
.
1
Cooler). Preliminary examination and intensity data collections were
carried out on a Kuma KM4CCD κ-axis diffractometer with
graphite-monochromated Mo KR radiation. The data were corrected
for Lorentz and polarization effects. No absorption correction was
applied. Data reduction and analysis were carried out with the Kuma
Diffraction (Wrocław) programs. The structures were solved by
heavy atom methods (program SHELXS97)59 and refined by the
full-matrix least-squares method on all F2 data using the SHELXL97
programs.60 The disorder exists in the complex (OTPP)FeIIICl2.
Molecules have four different orientations (1:1:1:1) in the unit cell,
but the Fe(1), Cl(1), and Cl(2) atoms have identical coordinates in
each case. These molecules differ by rotation along the Fe(1)-Cl-
(1) bond by 90°. Non-hydrogen atoms from the molecule with
immediately transferred to the H NMR spectrometer which was
maintained at 205 K. Samples of the (OTPP)FeI complex for the
EPR measurements were prepared by addition of PhMgBr to the
solution of (OTPP)FeIIICl2 directly in the 1H NMR tube which was
used in both experiments.
Acknowledgment. Financial support of the Polish State
Committee for Scientific Research KBN (Grant 4T 09A
14722) and the Foundation for Polish Science is kindly
acknowledged.
Supporting Information Available: Crystallographic data in
CIF format. VT NMR data for (OTPP)FeIIICl2, (OTPP)FeIICl, and
(OTPP)FeIII(CN)2 and NMR characteristics of [(OTPP)FeIII(CN)2]-.
This material is available free of charge via the Internet at
http://pubs.acs.org/.
(59) Sheldrick, G. M. SHELXS97, program for solution of crystal structures;
University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(60) Sheldrick, G. M. SHELXL97, program for crystal structure refinement;
University of Go¨ttingen: Go¨ttingen, Germany, 1997.
IC025718P
Inorganic Chemistry, Vol. 41, No. 22, 2002 5873