Copper(II) and copper(III) complexes of pyrrole-appended oxacarbaporphyrin

Article abstract of DOI:10.1021/ic700631t

The reaction of an O-confused porphyrin with a pendant pyrrole 4 and copper(II) acetate yields an organocopper-(III) diamagnetic complex 4-Cu(III) substituted at the C(3) position by the pyrrole and H. The transformation of 4-Cu(III), performed in aerobic conditions, gave a rare copper(II) organometallic compound 6-Cu(II). In the course of this process, the tetrahedral-trigonal rearrangement originated at the C(3) atom but effects the whole structure. The electron paramagnetic resonance spectroscopic features correspond to a copper(II) oxidation state. A crystallographic analysis of 6-Cu(II) confirmed the formation of a direct metal-C bond [Cu(II)-C 1.939(4) A]. It was found that the Cu(II) complex of O-confused oxaporphyrin is sensitive to oxidative conditions. The degradation of 6-Cu(II) to yield copper(II) tripyrrinone complexes has been observed, which was considered as a peculiar case of dioxygen activation in a porphyrin-like environment. This process is accompanied by regioselective oxygenation at the inner C to form the 2-oxa-3-(2′-pyrrolyl)-21-hydroxycarbaporphyrinatocopper(II) complex ((pyrr)OCPO)Cu^II (8). The reaction of 6-Cu(II) with hydrogen peroxide, performed under heterophasic conditions, resulted in quantitative regioselective hydroxylation centered at the internal C(21) atom, also producing 8. Treatment of 8 with acid results in demetalation to form the nonaromatic 21-hydroxy O-confused porphyrin derivative ((pyrr)OCPOH)H (9).

Full text of DOI:10.1021/ic700631t

Inorg. Chem. 2007, 46, 6575−6584
Copper(II) and Copper(III) Complexes of Pyrrole-Appended
Oxacarbaporphyrin
Miłosz Pawlicki, Izabela Kan´ska, and Lechosław Latos-Graz3yn´ski*
Department of Chemistry, UniVersity of Wrocław, 14 F. Joliot-Curie Street,
Wrocław 50 383, Poland
Received April 3, 2007
The reaction of an O-confused porphyrin with a pendant pyrrole 4 and copper(II) acetate yields an organocopper-
(III) diamagnetic complex 4-Cu(III) substituted at the C(3) position by the pyrrole and H. The transformation of
4-Cu(III), performed in aerobic conditions, gave a rare copper(II) organometallic compound 6-Cu(II). In the course
of this process, the tetrahedral
The electron paramagnetic resonance spectroscopic features correspond to a copper(II) oxidation state. A
crystallographic analysis of 6-Cu(II) confirmed the formation of a direct metal C bond [Cu(II) C 1.939(4) Å]. It was
−trigonal rearrangement originated at the C(3) atom but effects the whole structure.
−
−
found that the Cu(II) complex of O-confused oxaporphyrin is sensitive to oxidative conditions. The degradation of
6-Cu(II) to yield copper(II) tripyrrinone complexes has been observed, which was considered as a peculiar case of
dioxygen activation in a porphyrin-like environment. This process is accompanied by regioselective oxygenation at
the inner C to form the 2-oxa-3-(2′
-pyrrolyl)-21-hydroxycarbaporphyrinatocopper(II) complex ((pyrr)OCPO)CuII (8).
The reaction of 6-Cu(II) with hydrogen peroxide, performed under heterophasic conditions, resulted in quantitative
regioselective hydroxylation centered at the internal C(21) atom, also producing 8. Treatment of 8 with acid results
in demetalation to form the nonaromatic 21-hydroxy O-confused porphyrin derivative ((pyrr)OCPOH)H (9).
Introduction
Following such an approach, we have characterized
O-confused oxaporphyrin 3, albeit in its dicationic form,8
and S-confused thiaporphyrin 2.5 In contrast to S-confused
thiaporphyrin 2, the oxa analogue 3 is extremely reactive
toward nucleophilic attack at peripheral position 3, which
results in aromatization of the macrocycle and the formation
of derivatives like 4 and 5, both formally related to the
product of 2-oxa-21-carbaporphyrin hydrogenation.8,9 Thus,
the macrocyclic delocalization and aromaticity in 3 is easily
switched on and off by reversible addition/elimination of a
nucleophile at the position C(3), coupled with tetrahedral-
trigonal conversion of C(3). Notably, oxidation of the
hydroxy analogue of 5 yields carbaporpholactone 7, which
contains the lactone functionality instead of the regular furan
moiety.8
A heteroatom confusion (X-confusion) concept, first
exemplified by a porphyrin-2-aza-21-carbaporphyrin couple
1,1,2 corresponds formally to an interchange of a heteroatom
with a â-methine group, i.e., to a step that transforms the
regular 21-X-heteroporphyrin into its “X-confused” isomer.3,4
This strategy resulted in the formation of thia- 25-7 and oxa
analogues 38,9 of N-confused porphyrin 1, where the S or O
atoms are placed at the macrocyclic perimeter. The C atom
of the heterocyclic subunit is directed toward the center of
the macrocyclic crevice (Chart 1).
* To whom correspondence should be addressed. E-mail: llg@
wchuwr.chem.uni.wroc.pl.
(1) Chmielewski, P. J.; Latos-Graz˘yn´ski, L.; Rachlewicz, K.; Głowiak,
T. Angew. Chem., Int. Ed. Engl. 1994, 33, 779.
In general, syntheses of carbaporphyrinoids, including
those obtained following the X-confusion approach,3 allow
an exploration of organometallic chemistry in a porphyrin-
(2) Furuta, H.; Asano, T.; Ogawa, T. J. Am. Chem. Soc. 1994, 116, 767.
(3) Pawlicki, M.; Latos-Graz˘yn´ski, L. Chem. Rec. 2006, 6, 64.
(4) Furuta, H.; Maeda, H.; Osuka, A. Chem. Commun. 2002, 1795.
(5) Sprutta, N.; Latos-Graz˘yn´ski, L. Tetrahedron Lett. 1999, 40, 8457.
(6) Chmielewski, M. J.; Pawlicki, M.; Sprutta, N.; Szterenberg, L.; Latos-
Graz˘yn´ski, L. Inorg. Chem. 2006, 45, 8664.
(10) 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,
Chapter 14, pp 361-416.
(7) Szterenberg, L.; Sprutta, N.; Latos-Graz˘yn´ski, L. J. Inclusion Phenom.
2001, 41, 209.
(8) Pawlicki, M.; Latos-Graz˘yn´ski, L. J. Org. Chem. 2005, 70, 9123.
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10.1021/ic700631t CCC: $37.00
Published on Web 07/04/2007
© 2007 American Chemical Society
Inorganic Chemistry, Vol. 46, No. 16, 2007 6575

Pawlicki et al.
Chart 1. Selected X-Confused meso-Tetraarylcarbaporphyrinoids
like environment. Therefore, the coordination properties of
the first reported carbaporphyrinoid (N-confused carbapor-
phyrin) 1 have been studied for a large variety of metal
ions.4,10-15 The remarkable flexibility of the N-confused
porphyrin is reflected by the formation of various coordina-
tion modes in macrocyclic environments, with or without
the formation of a direct metal-C bond.1,16,17 Importantly,
atypical oxidation states of metal ions trapped in organo-
metallic environments have been identified.18-24 The coor-
dination properties were also explored for carbocyclic
analogues as exemplified by m-benziporphyrin,25-28 azuli-
porphyrin,29 and benzocarbaporphyrin.30
The coordination chemistry of O-confused oxaporphyrins
has been reported for a limited number of metal ions. The
reported coordination features resemble those of N-confused
porphyrins. Thus, an insertion of metal ions into O-confused
oxaporphyrin derivatives afforded organometallic complexes
of 3 (Ag(III)),8 4 (Ag(III)),9 5 (Ag(III)),8 6 (Ag(III), Ni(II),
and Pd(II))9 and 7 (Ag(III)).8 Significantly, an accommoda-
tion of Ni(II) or Pd(II) by 4 is linked to a dehydrogenation
step, which results in the formation of a “true” O-confused
oxaporphyrin frame of 6 but with a pendant pyrrole. The
pyrrole-appended O-confused oxaporphyrin 6 acts also as a
monoanionic ligand toward Zn(II) and Cd(II) cations. Three
N atoms and the C(21)H fragment of the inverted furan
occupy equatorial positions. The proximity of the furan
fragment to the metal ion induces direct scalar couplings
between the spin-active nucleus of the metal (111/113Cd) and
(12) Srinivasan, A.; Furuta, H. Acc. Chem. Res. 2005, 38, 10.
(13) Chmielewski, P. J.; Latos-Graz˘yn´ski, L. Coord. Chem. ReV. 2005, 249,
2510.
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(15) Maeda, H.; Furuta, H. Pure Appl. Chem. 2006, 78, 29.
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Soc. 1996, 118, 5690.
(17) Furuta, H.; Morimoto, T.; Osuka, A. Inorg. Chem. 2004, 43, 1618.
(18) Chmielewski, P. J.; Latos-Graz˘yn´ski, L. Inorg. Chem. 1997, 36, 840.
(19) Furuta, H.; Ogawa, T.; Uwatoko, Y.; Araki, K. Inorg. Chem. 1999,
38, 2676.
1
the adjacent H nucleus.31
In light of these observations, we have turned our attention
to organocopper chemistry of the O-confused porphyrin
macrocycle. In general, the organometallic chemistry of
copper is nearly exclusively focused on the metal oxidation
state +1.32 Electron-rich organocopper(I) compounds are
widely applied as useful reagents in numerous organic
syntheses.33 Transient organocopper(III) species were con-
sidered in the mechanism of a multiple bond activation Via
reactive π complexes. Their transformations into the σ-carbon
copper(III) intermediates were followed by reductive
elimination.34-37 It was also demonstrated that doubly
(20) Chmielewski, P. J.; Latos-Graz˘yn´ski, L.; Schmidt, I. Inorg. Chem.
2000, 39, 5475.
(21) Chmielewski, P. J.; Latos-Graz˘yn´ski, L. Inorg. Chem. 2000, 39, 5639.
(22) Rachlewicz, K.; Wang, S.-L.; Ko, J.-L.; Hung, C.-H.; Latos-Graz˘yn´ski,
L. J. Am. Chem. Soc. 2004, 126, 4420.
(23) Maeda, H.; Osuka, A.; Ishikawa, Y.; Aritome, I.; Hisaeda, Y.; Furuta,
H. Org. Lett. 2003, 5, 1293.
(24) Bohle, D. S.; Chen, W.-C.; Hung, C.-H. Inorg. Chem. 2002, 41, 3334.
(25) Ste¸pien´, M.; Latos-Graz˘yn´ski, L. Acc. Chem. Res. 2005, 38, 88.
(26) Hung, C.-H.; Chang, F.-C.; Lin, C.-Y.; Rachlewicz, K.; Ste¸pien´, M.;
Latos-Graz˘yn´ski, L.; Lee, G.-H.; Peng, S.-M. Inorg. Chem. 2004, 43,
4118.
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44, 9779.
(27) Ste¸pien´, M.; Latos-Graz˘yn´ski, L.; Szterenberg, L.; Panek, J.; Latajka,
(32) van Koten, G.; James, S. L.; Jastrzebski, J. T. B. H. In ComprehensiVe
Organometallic Chemistry II; Wardell, J. L., Abel, E. W. W., Stone,
F. G. A., Wilkinson, G., Eds.; Elsevier Science Ltd.: London, 1995;
Chapter 3.
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Z. J. Am. Chem. Soc. 2004, 126, 4566.
(28) Ste¸pien´, M.; Latos-Graz˘yn´ski, L. Chem.sEur. J. 2001, 7, 5113.
(29) Lash, T. D.; Colby, D. A.; Graham, S. R.; Ferrence, G. M.; Szczepura,
L. F. Inorg. Chem. 2003, 42, 7326.
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Lett. 2004, 6, 549.
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6576 Inorganic Chemistry, Vol. 46, No. 16, 2007

Complexes of Pyrrole-Appended Oxacarbaporphyrin
Chart 2. Cu(II) Complexes of N-Confused Porphyrins
N-confused porphyrin acts as a complexing agent capable
of stabilizing the copper(III) oxidation state.38,39 Several
stable organometallic complexes of copper(III) were char-
acterized by X-ray crystallography.38-42
These authors discovered an interconversion between the Cu-
(II) and Cu(III) complexes of N-confused porphyrin, which
is stimulated by the accompanying protonation/deprotonation
of the perimeter N atom.44 N-Confused porphyrin undergoes
a Cu(II)-assisted degradation to afford aryl-substituted tripyr-
rinone.45 Formation of a Cu(II) N-confused porphyrin species
is involved in the mechanism. Apart from N-confused
porphyrin, the N-confused calix[4]phyrin acts as an orga-
nometallic ligand, which stabilizes rare organocopper(II)
complexes.46
As a part of our continuing program of investigating the
organometallic chemistry of paramagnetic carbaporphy-
rinoids, here we report on the synthesis and spectroscopic
characterization of Cu(II) complexes of pyrrole-appended
O-confused porphyrin. These studies explore new controlling
macrocyclic factors that potentially are of importance in the
emerging field of Cu(II) organometallic chemistry. The
peculiar flexibility of the O-confused oxaporphyrin structure,
expected to shape the stability and reactivity of the resulting
Cu(II) and Cu(III) complexes, has been a matter of specific
interest.
In contrast to Cu(I) and Cu(III), organocopper(II) com-
plexes are extremely rare. Initially, the transient σ-alkyl
adducts of Cu(II) were postulated to form in the reactions
of Cu(I) complexes with aliphatic radicals obtained by pulse-
radiolysis techniques.43 Eventually, organocopper(II) com-
pounds were synthesized by applying an efficient protection
of the Cu(II)-C bond in the coordination (CNNN) core of
N-confused porphyrin.20 The combination of electron para-
2
magnetic resonance (EPR) and H NMR yielded detailed
insight into the electronic structure of these organocopper-
(II) species.20 As a result of steric constraints imposed by
the ligand geometry, the C(21) atom creates two distinctly
different types of the Cu(II)-C(21) bond. Specifically, the
equatorial macrocycle may act as an sp2 σ-carboanion, e.g.,
(H)1-Cu(II) and (Me)1-Cu(II) (Chart 2). Alternatively, as
illustrated by (Me)1Me-Cu(II)Cl, the C-methylated pyrrole
seems to coordinate to the Cu in the η1-fashion but the
coordinating C(21) atom preserves trigonal geometry.
Subsequently, Furuta and co-workers reported that N-
confused porphyrin bearing pentafluorophenyl groups forms
the square-planar structure as elucidated by X-ray analyses.23
Results and Discussion
Cu Complexes of Pyrrole-Appended O-Confused Ox-
aporphyrin. The reaction of copper(II) acetate and 4 under
mild conditions [tetrahydrofuran (THF), reflux, 30 min]
resulted in quantitative formation of 4-Cu(III) (Scheme 1).
The UV-vis spectrum of 4-Cu(III) (Figure 1) presents
the pattern typical for aromatic porphyrin derivatives with
the intense Soret band, and the set of Q bands in the 350-
700 nm region, comparable to the diamagnetic silver(III)
O-confused oxaporphyrin complexes.9 The high values of
(35) Fernandez de la Pradilla, R.; Rubio, M. B.; Marino, J. P.; Viso, A.
Tetrahedron Lett. 1992, 33, 4985.
(36) Nakamura, E.; Mori, S.; Morokuma, K. J. Am. Chem. Soc. 1997, 119,
4900.
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(38) Furuta, H.; Maeda, H.; Osuka, A. J. Am. Chem. Soc. 2000, 122, 803.
(39) Maeda, H.; Osuka, A.; Furuta, H. J. Am. Chem. Soc. 2003, 125, 15690.
(40) Eujen, H.; Hoge, B.; Brauer, D. J. J. Organomet. Chem. 1996, 519,
7.
(41) Neumann, D.; Roy, T.; Tebbe, K.-F.; Crump, W. Angew. Chem., Int.
Ed. Engl. 1993, 32, 1482.
(42) Willert-Porada, M. A.; Burton, D. J.; Baenzinger, N. C. Chem.
Commun. 1989, 1633.
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1995, 14, 5670.
(44) Maeda, H.; Ishikawa, Y.; Matsuda, T.; Osuka, A.; Furuta, H. J. Am.
Chem. Soc. 2003, 125, 11822.
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(46) Furuta, H.; Ishizuka, T.; Osuka, A.; Uwatoko, Y.; Ishikawa, Y. Angew.
Chem., Int. Ed. 2001, 40, 2323.
Inorganic Chemistry, Vol. 46, No. 16, 2007 6577

Pawlicki et al.
Scheme 1. Synthesis of Copper O-Confused Oxaporphyrins
Figure 2. 1H NMR spectrum of 4-Cu(III) (CDCl3, 298 K). The inset
presents resonances of the pendant pyrrole ring. Peak labels denote proton
groups: pyrr-pyrrole; o, m, and p are ortho, meta, and para positions of
meso-aryls (Ph and Tol), respectively.
The â-H resonances of 4-Cu(III) are observed in the region
8.1-7.6 ppm (Figure 1). In comparison to the structurally
analogous silver(III) O-confused oxaporphyrin, the â-H
resonances of 4-Cu(III) are relocated slightly upfield as the
respective resonances of 4-Ag(III) are placed at the 8.8-
8.3 ppm region.9 In contrast, isoelectronic Ag(III)-Cu(III)
N-confused complexes reveal very similar spectroscopic
features (â-H: 9.5-8.6 ppm).19,44 The electronic structure
of 4-Cu(III) can actually be described by the resonance
between two canonic forms (P3-)Cu(III) T (P2•-)Cu(II),
where the second one brings around the paramagnetic
contribution reflected by the described differences in the
chemical shifts of 4-Cu(III) and 4-Ag(III). An analogous
situation was previously observed for metallotriarylcorroles.
The â-H resonances are in the region typical for aromatic
compounds (9.20-8.10 ppm) when the Ag(III) ion is
bound,47 while a structurally similar Cu(III) complex presents
their pyrrolic lines in the 7.9-7.3 ppm region.48,49 A striking
example of such a difference was reported by Pacholska et
al. for heterobimetallic face-to-face bis(corrole) systems.50
There a simultaneous coordination of Cu(III) and Ag(III)
yielded two sets of â-H signals, which were easily assigned
to Ag(III) (9.0-8.4 ppm) and Cu(III) (7.7-6.8 ppm)
subunits.
extinction coefficients observed for 4-Cu(III) confirm the
macrocyclic aromaticity.
The 1H NMR spectrum of 4-Cu(III) (Figure 2) illustrates
the characteristic aromatic features of the species, which are
consistent with the electronic spectrum. The NMR data
comply with the tetrahedral geometry around C(3) charac-
teristic for 4, which is preserved after coordination.9 The
presence of H(3) was confirmed indirectly with help of a
1H-13C NMR correlation experiment.
The heteronuclear multiple-quantum coherence (HMQC)
map allowed one to identify the C(3) signal at 86.9 ppm,
which remains in good agreement with the previously
observed 13C NMR chemical shift (85.3 ppm) of the
tetrahedral C atom determined for 4. A characteristic pattern
of the pendant pyrrole ring resonances was also observed.
We found that the 4-Cu(III) species is extremely unstable
in aerobic conditions. In the presence of dioxygen, 4-Cu-
(III) readily undergoes a spontaneous conversion to form a
paramagnetic Cu(II) compound 6-Cu(II), where the metal
ion is bonded to three N atoms and one C atom of an inverted
furan. As shown in Scheme 1, the profound rearrangement
of the macrocyclic structure from 4 to 6 takes place, which
(47) Bru¨ckner, C.; Barta, C. A.; Brin´as, R. P.; Krause Bauer, J. A. Inorg.
Chem. 2003, 42, 1673.
(48) Will, S.; Lex, J.; Vogel, E.; Schmickler, H.; Gisselbrecht, J.-P.;
Haubtman, C.; Bernard, M.; Gross, M. Angew. Chem., Int. Ed. 1997,
36, 357.
(49) Bru¨ckner, C.; Brinas, R. P.; Krause-Bauer, J. A. Inorg. Chem. 2003,
42, 4495.
(50) Pacholska, E.; Espinoza, E.; Guilard, R. Dalton Trans. 2004, 3181.
Figure 1. UV-vis spectra for 4-Cu(III) (red), 6-Cu(II) (green), and 8
(orange).
6578 Inorganic Chemistry, Vol. 46, No. 16, 2007

Complexes of Pyrrole-Appended Oxacarbaporphyrin
3). The electronic spectrum of 6-Cu(III) is completely
different from starting 6-Cu(II) resembling that of Ag(III)
inserted in 6, i.e., 6-Ag(III) (Figure 4).9
The spectrum shows the intense Soret-like band at 496
nm accompanied by comparable ones at 662 and 750 nm.
Previously, we have demonstrated that the peculiar flexibility
of pyrrole-appended oxacarbaporphyrin is capable of stabi-
lizing metal(II) (Ni(II) and Pd(II)) or metal(III) (Ag(III)) ions
by fine adjusting of its own molecular/electronic structure.9,31
Accordingly, the appended pyrrole ring incorporation into
the π-delocalization pathway can be tuned. Consequently,
the charge of the macrocyclic cavity varies from -2 to -3,
fitting the requirements of the coordinated metal ion, in this
particular case a Cu(II)-Cu(III) couple.
Crystal Structure of 6-Cu(II). The structure of 6-Cu(II)
has been determined by X-ray crystallography. The O-
confused Cu(II) complex 6-Cu(II) crystallizes in space group
P21/c. The overall geometry observed for 6-Cu(II) is
presented in Figure 5. The macrocycle is only slightly
distorted from planarity. The dihedral angle between the
macrocyclic and pyrrole-appended planes reflects the biphe-
nyl-like arrangement and equals 23.8°, with the NH group
pointing toward the adjacent phenyl ring on the 5 position.
This value is comparable to the previously reported one
(26.4°) observed for crystal structure of a Ni(II) complex of
pyrrole-appended O-confused oxaporphyrin 6-Ni(II).9 This
angle is significantly smaller than the dihedral angles between
the meso-aryl rings and the oxacarbaporphyrin plane [phenyl-
(5) 66.9°, phenyl(20) 58.0°, p-tolyl(10) 64.0°, and p-tolyl-
(15) 55.3°]. For comparison, a coplanar arrangement of
pyrrole and furan rings was reported for unsubstituted simple
2-(2′-furyl)pyrrole in solution.57,58
Figure 3. EPR spectra [X band, dichloromethane/toluene (80/20), 77 K]:
(A) 6-Cu(II) (microwave frequency 9.5851, microwave power 40 mW,
modulation amplitude 7.73 G, modulation frequency 100 kHz); (B) 8
(microwave frequency 9.4277, microwave power 40 mW, modulation
amplitude 6.81 G, modulation frequency 100 kHz). Insets in both traces
present the corresponding isotropic spectra at 298 K.
is permitted through the already established flexibility of the
inverted oxaporphyrin.9 Previously, we have observed these
two different coordination modes correlated with a central
metal oxidation state albeit never for the same element. A
direct insertion of Cu(II) into 6 produced 6-Cu(II) with a
quantitative yield. The Cu(II) O-confused complex presents
the UV-vis spectra (Figure 1) comparable to those of 6-Ni-
(II) and 6-Pd(II), as expected for the metal(II) ions within a
similar macrocyclic environment.9
The EPR spectra recorded for 6-Cu(II) are presented in
Figure 3. The isotropic 63,65Cu hyperfine constants (Table
1) are relatively small when compared to the copper(II)
porphyrins51 and copper(II) monoheteroporphyrins10,52-54
although similar to those determined for copper(II) diox-
aporphyrin.54 However, these values are comparable to the
data of copper(II) N-confused porphyrin.20,55
The Cu(II)-N distances in 6-Cu(II) [Cu-N(22) 2.020(3)
Å, Cu-N(23) 1.977(3) Å, and Cu-N(24) 2.065(3) Å] are
comparable to those in the nearly planar copper(II) porphy-
rins59 or copper(II) octaethyl-5-oxaporphyrin.60 The Cu(II)-
C(21) bond length equals 1.939(4) Å. There are only two
other reported examples of X-ray analysis on organometallic
Cu(II) complexes characterized. The Cu(II)-N and Cu(II)-
C(21) distances found for copper(II) N-confused calix[4]-
phyrin [Cu(II)-C(21) 2.007(4) Å, Cu(II)-N(22) 2.076(4)
Å, Cu(II)-N(23) 2.010(3) Å, and Cu(II)-N(24) 2.056(4)]
are slightly longer than those reported for 6-Cu(II), which
may be related to the differences in the extent of conjugations
encountered in both macrocycles. Copper(II) N-confused
porphyrin bearing pentafluorophenyl groups forms a square-
planar structure as elucidated by X-ray analyses. The average
bond lengths between Cu(II) and ligand atoms are 1.980(9)
and 2.018(9) Å,23 but the crystal structure disorder excludes
the detailed bond length discussion.
The absolute values of the spin-Hamiltonian parameters
determined for anisotropic spectra of frozen solutions do not
differ from those obtained for typical Cu(II) complexes.56
This fact indicates that the orbital containing unpaired
electrons (SOMO) involves a predominant metal contribu-
tion.
The UV-vis titration of 6-Cu(II) with Br2 results in one-
electron oxidation to produce Cu(III) species 6-Cu(III) (Chart
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C.; Steglich, W. J. J. Chem. Soc., Perkin Trans. 2 1981, 127.
(59) Scheidt, W. R.; Reed, C. R. Chem. ReV. 1981, 81, 543.
(60) Koerner, R.; Olmstead, M. M.; Ozarowski, A.; Phillips, S. L.; Van
Calcar, P. M.; Winkler, K.; Balch, A. L. J. Am. Chem. Soc. 1998,
120, 1274.
(56) Hathaway, B. J. Struct. Bonding (Berlin) 1984, 37, 55.
Inorganic Chemistry, Vol. 46, No. 16, 2007 6579

Pawlicki et al.
Table 1. Spin-Hamiltonian Parameters of Cu(II) Complexes of O-Confused Oxaporphyrins
Cu
Cu
N
compound
-A|Cu
-A
g|
g
-Ao
go
-Ao
ref
6-Cu(II)a
154
169
143
140
154
151
-29
2.134
2.218
2.139
2.142
2.190
2.195
2.029
2.046
2.057
2.054, 2.026
2.050
30
76.8
23
28.5
60.0
59.2
2.073
2.086
2.070
2.079
2.110
2.113
21.6
13.2
18.3
20.0
13.0
12.9
this paper
this paper
20
20
20
20
8b
30.6
(H)1-Cu(II)
(Me)1-Cu(II)
(H)1H-Cu(II)Cl
(Me)1H-Cu(II)Cl
-37
-27
13
13
2.052
a The 14N hyperfine constant in the perpendicular region is 22.3, 13.1 and that in the parallel region is 18.7. b The 14N hyperfine constant in the perpendicular
region is 13.8.
Chart 3
Reactivity of 6-Cu(II) toward Dioxygen. Copper(II)
O-confused oxaporphyrin with appended pyrrole ring 6-Cu-
(II) dissolved in CHCl3 undergoes reactions with dioxygen
over a period of hours. The complex 6-Cu(II) was predomi-
nantly ring-opened through oxidative cleavage to form the
open-chain copper(II) tripyrrrole species identified as copper-
(II) 14-benzoyl-5,10-bis(p-tolyl)-1-oxotriphyrin complex 7a
(Scheme 2).
In the course of oxygenolysis, the O-confused furan
fragment with an appended pyrrole ring and the adjacent
C6H5-Cmeso units have been extruded. The cleavage of 6-Cu-
(II) has been accompanied by oxygenation of 6-Cu(II) at the
C(21) position, which led to the formation of copper(II)
Figure 5. Crystal structure of 6-Cu(II). The upper trace presents a
perspective view and the bottom one a side view (aryl substituents are
omitted for clarity).
5,20-diphenyl-10,15-ditolyl-2-oxa-3-(2′-pyrrolyl)-21-hydrox-
ycarbaporphyrinatocopper(II) (8) albeit in a relatively low
yield. This species has been found to be, contrary to 6-Cu-
(II), resistant to cleavage at the meso positions. Thus, in the
course of this process, a new type of core-modified porphyrin
has been identified. The macrocycle incorporates 3-hydroxy-
furan into the porphyrin-like structure. Both compounds are
stable and have been purified by the standard chromato-
graphic procedures.
Identification of 7a has been facilitated because an
identical complex was previously isolated and fully charac-
terized by Furuta and co-workers as a degradation product
of N-confused porphyrins in the presence of Cu(II).45 Thus,
the spectroscopic features of 7a matched those of copper-
(II) tripyrrin formed from copper(II) N-confused porphyrin.45
In order to explore the regioselectivity of oxidative
degradation, an analogue of 4a, i.e., 20-phenyl-5,10,15-
tritolyl-2-oxa-3-hydro-3-(2′-pyrrolyl)-21-carbaporphyrin (4b),
was synthesized. The oxidative degradation afforded two
feasible copper(II) tripyrrinone complexes, 7a and 7b (70:
30; Scheme 3), as was unambiguously confirmed by mass
spectra [7a, m/z 583.2 (M + H)+; 7b, m/z 597.2 (M + H)+].
In the case of degradation of copper(II) N-confused
porphyrin, the specific substitution at the meso position by
2-pyridyl resulted in a regioselective extrusion.45 The first
Figure 4. UV-vis spectra for 6-Cu(III) (blue) and 6-Ag(III) (red).
6580 Inorganic Chemistry, Vol. 46, No. 16, 2007

Complexes of Pyrrole-Appended Oxacarbaporphyrin
Scheme 2. Reactivity toward Dioxygen
heterophasic conditions, resulted in quantitative, regioselec-
tive hydroxylation centered at the internal C(21) atom
(Scheme 4).
A specific reactivity of metallocarbaporphyrinoids centered
on internal C-H or C-M units was previously reported.
For instance, m-benziporphyrin undergoes selective acetoxy-
lation, chlorination, or pyridination.26,28,63 The iron and
manganese N-confused porphyrin react with dioxygen. As a
consequence, 2-azacarbaporphyrin acquires oxofunctionality
[C(21)O] in the coordination core.64,65 Finally, an attempt
to insert Cu(II) into azuliporphyrin afforded a Cu(II)
complex, where the Cu(II) ion is bounded by three N atoms
and the O atom of the 21-hydroxy group.66 The EPR
spectrum recorded for 8 (Figure 3, trace B, and Table 1)
presents a pattern clearly different from that of the hydroxy-
lation substrate 6-Cu(II), but it resembles those of copper-
(II) N-confused porphyrin complexes, where the C(21) atom
was protonated.20
Treatment of 8 with acid results in demetalation to form
21-hydroxy derivative 9 (Scheme 4). Significantly, for the
structural conclusions, the reversed process, i.e., insertion
of Cu(II) into 9, gives 8 quantitatively. Previously, a keto-
enol tautomerization has been observed for a group of
hydroxylated derivatives derived from N-confused porphy-
rin,65 m-benziporphyrin,67 and azuliporphyrin.66 On the
contrary, the 21-hydroxycarbaporphyrinoid structure is en-
tirely preferred for 9. Presumably, the presence of appended
pyrrole and O at the macrocycle perimeter effectively blocks
any possibility of transformation into a keto tautomer of 9.
step of oxygenolysis involved the CR-Cmeso bond adjacent
to the N atom of the N-confused pyrrole ring. The cleaved
meso-phenyl moiety was located next to the â-C of the same
ring. The determined difference of the regioselectivities of
copper(II) N- and O-confused porphyrins may reflect a
difference in the nature of the X-confused ring and/or in the
choice of meso-aryl substituents. Presumably, the 2-pyridyl
moiety favors cleavage of the CR-Cmeso(2-pyridyl) bond in
the first oxygenolysis step in comparison to the alternative
CR′-Cmeso(phenyl) one. The steric/electronic factor introduced
in the case investigated here seems not to be essential,
considering the minor differences in the structures of meso
substituents adjacent to the O-confused ring, which are,
however, sufficient to distinguish two feasible products.
The degradation of copper(II) N- and O-confused porphy-
rins can be considered as a peculiar case of dioxygen
activation in the porphyrin-like environment. Contrary to N-
and O-confused derivatives, regular copper(II) porphyrins
are relatively stable toward dioxygen. In this context, it is
essential to recall that copper(II) octaethyl(meso-hydroxy)-
porphyrins, (OEPOH)Cu(II), undergo oxidation by dioxygen
to form a dinuclear Cu(II) complex that is composed of a
copper(II) meso-substituted porphyrin portion that is attached
through an ester linkage to a helical copper(II) tetrapyrrole
that has been ring-opened through oxidative cleavage of a
second molecule of (OEPOH)Cu(II).61 This oxidative ring-
opening reaction resembles that of natural heme catabolism.60
Independently synthesized Cu(II) complexes of octaethyl-
bilindione react with dioxygen, which results in cleavage of
the tetrapyrrolic ligand to form a Cu(II) complex containing
a propentdyopent class dipyrrole.62
1
The H NMR spectrum of 9 (Figure 6) contains three AB
systems assigned to the â-pyrrolic protons [H(7) 7.25, H(8)
6.69 (3J ) 4.5 Hz); H(13) 6.92, H(12) 6.70 (3J ) 4.6 Hz);
H(18) 6.72, H(17) 6.59 (3J ) 4.6 Hz]. The complete
assignment was performed on the basis of several two-
dimensional experiments (COSY, NOESY, HMQC, and
HMBC). Two broad resonances at 11.49 and 8.87 ppm were
identified as NH and OH signals, respectively. The COSY
experiment at low temperature (220 K), where scalar
couplings between already assigned â-H’s and an appropriate
NH resonance allowed the unambiguous localization of the
NH hydrogen. The spectral range observed for 9 suggests
that the macrocyclic π-delocalization pathway is blocked.
Thus, the macrocyclic aromaticity is lowered. This is the
first example of an O-confused porphyrin where the â-H
resonances are located in the region typical for heterocyclic
aromaticity of its five-membered components. The previously
described macrocycles with an inverted furan ring present
delocalization that results in downfield-shifted signals of
â-H’s.8,9,31 However, nonaromatic structures as reflected by
the characteristic chemical shift values were observed for
(63) Ste¸pien´, M.; Latos-Graz˘yn´ski, L. Org. Lett. 2003, 5, 3379.
(64) Hung, C.-H.; Chen, W.-C.; Lee, G.-H.; Peng, S.-M. Chem. Commun.
2002, 1516.
(65) Hung, C.-H.; Wang, S.-L.; Ko, J.-L.; Peng, C.-H.; Hu, C.-H.; Lee,
M.-T. Org. Lett. 2004, 6, 1393.
21-Hydroxy O-Confused Oxaporphyrin. The reaction
of 6-Cu(II) with hydrogen peroxide, performed under
(61) Phillips, S.; Noll, B. C.; Olmstead, M. M.; Balch, A. L. Can. J. Chem.
2001, 79, 922.
(62) Balch, A. L.; Mazzanti, M.; Noll, B. C.; Olmstead, M. M. J. Am.
Chem. Soc. 1993, 115, 12206.
(66) Colby, D. A.; Ferrence, G. M.; Lash, T. D. Angew. Chem., Int. Ed.
2004, 43, 1346.
(67) Ste¸pien´, M.; Latos-Graz˘yn´ski, L.; Szterenberg, L. J. Org. Chem. 2007,
72, 2259.
Inorganic Chemistry, Vol. 46, No. 16, 2007 6581

Pawlicki et al.
Scheme 3. Degradation of Copper(II) Oxacarbaporphyrin
Scheme 4. Hydroxylation of Copper(II) Oxacarbaporphyrin
requirements of Cu ions, via a modification centered at the
2-(2′furyl)pyrrole moiety, have been explored. Thus, the
present investigations offer evidence for stabilization of
unusual organocopper(II) species via the very efficient
protection of the Cu(II)-C bond by encapsulating the
coordinated Cu(II) center in the core of 2-oxa-21-carbapor-
phyrin (NNNC). The true O-confused porphyrin readily
accommodates Cu(II), as confirmed by EPR parameters.
Significantly, the crystallographic analysis confirms the
formation of the short Cu(II)-C bond [1.939(4) Å]
because the equatorial macrocycle acts similarly to an sp2
σ-carbanion.
One can realize that the oxidative ring opening of copper-
(II) O-confused oxaporphyrin to form a copper(II) tripyr-
rinone complex in the presence of dioxygen and the
regioselective C(21) hydroxylation can be related to heme
degradation that utilizes dioxygen with heme oxygenase or
coupled oxidation conditions.69,70 It was previously shown
that heme degradation can proceed beyond the ring opening
that produces an iron biliverdin complex as well as ver-
doheme. For instance, octaethylverdoheme and iron biliverdin
complexes are converted into iron(III) hexaethyltripyrrone.71
The reaction of (meso-NH2OEP)Fe(II)(Py)2 with dioxygen
produced a metastable, ring-opened tetrapyrrole that has been
oxygenated at a second meso position and that served as a
model for the oxidative removal of the terminal pyrrole
group.71 In this context, the mechanistic aspects of the process
of cleavage of copper(II) O-confused oxaporphyrin and in
particular its relevance to the coupled oxidation mechanism
are of current interest.
S-confused thiaporphyrin,5 m-benziporphyrin,28 and 3-aza-
m-benziporphyrin (N-confused pyriporphyrin).68
Conclusion
Thus, this work revealed that an O-confused porphyrin
with an appended pyrrole ring offers a unique macrocyclic
environment in which to form organocopper compounds and
to control their reactivity. In particular, the specific routes
to tuning carbaporphyrinoid properties, according to the
Experimental Section
Solvents and Reagents. Dichloromethane-d2 (CIL) was used as
received. Chloroform-d (CIL) was passed through basic Al2O3.
Macrocyles 4a and 6 were obtained as previously described.9,31
20-Diphenyl-5,10,15-tritolyl-2-oxa-3-hydro-3-(2′-pyrrolyl)-21-
carbaporphyrin (4b). Macrocycle 4b was obtained by a previously
described procedure9 using 2-phenylhydroxymethyl-4-p-tolylhy-
droxymethylfuran as a source of the inverted furan. UV-vis (CH2-
Cl2, λmax/nm (log ꢀ)): 439 (5.37), 534 (4.30), 569 (4.16), 622 (3.98),
(68) Mys´liborski, R.; Latos-Graz˘yn´ski, L. Eur. J. Org. Chem. 2005, 5039.
(69) Balch, A. L.; Latos-Graz˘yn´ski, L.; Noll, B. C.; Olmstead, M. M.; Safari,
N. J. Am. Chem. Soc. 1993, 115, 9056.
Figure 6. 1H NMR spectrum of 9 (CDCl3, 298 K). The inset presents the
downfield region with NH and OH protons. Peak labels follow systematic
position numbering of the macrocycle or denote proton groups: o, m, and
p are ortho, meta, and para positions of meso-aryls (Ph and Tol), respectively.
(70) Kalish, H.; Latos-Graz˘yn´ski, L.; Balch, A. L. J. Am. Chem. Soc. 2000,
122, 12478.
(71) Kalish, H.; Lee, H. M.; Olmstead, M. M.; Latos-Graz˘yn´ski, L.; Rath,
S. P.; Balch, A. L. J. Am. Chem. Soc. 2003, 125, 4674.
6582 Inorganic Chemistry, Vol. 46, No. 16, 2007

Complexes of Pyrrole-Appended Oxacarbaporphyrin
1
3
Table 2. Crystal Data for 6-Cu(II) with Refinement Details
680 (4.25). H NMR (CDCl3, 298 K): δ 8.49 (d, 1H, J ) 4.6
Hz), 8.47 (d, 1H, 3J ) 4.6 Hz), 8.46 (d, 1H, 3J ) 4.6 Hz), 8.44 (d,
1H, 3J ) 4.6 Hz), 8.43 (d, 1H, 3J ) 4.6 Hz), 8.28 (d, 1H, 3J ) 4.6
Hz), 8.11 (m, 2H), 8.05 (s, 1H), 8.04 (m, 2H), 7.99 (m, 1H), 7.90
(bs, 1H), 7.67-7.63 (m, 2H), 7.55 (tt, 1H), 7.52-7.45 (m, 5H),
7.41 (bs, 1H), 7.20 (bs, 1H), 7.16 (bs, 1H), 7.14 (bs, 1H), 6.30 (m,
1H), 5.82 (m, 1H), 5.50 (m, 1H), 2.66 (s, 3H), 2.65 (s, 3H), 2.54
(s, 3H), -1.34 (bs, 2H), -5.07 (s, 1H). 13C NMR (CDCl3, 298 K):
δ 160.2, 152.9, 152.4, 143.6, 140.1, 139.3, 139.29, 139.2, 138.4,
137.5, 137.3, 137.2, 137.0, 135.1, 134.4, 134.3, 134.2, 134.04,
134.0, 133.8, 133.6 (bs), 132.1, 131.8, 130.8 (bs), 130.2, 128.6 (bs),
127.8, 127.6, 127.5, 127.2, 126.3, 126.2, 123.1, 123.0, 121.1, 120.2,
117.7, 112.6, 109.1, 108.2, 106.5, 106.4, 105.1, 85.2, 21.5, 21.5,
21.4. HRMS: m/zcalc 724.3170 (calcd 724.3202 for C51H40N4O).
5,20-Diphenyl-10,15-ditolyl-2-oxa-3-hydro-3-(2′-pyrrolyl)-21-
carbaporphyrinatocopper(III) (4-Cu(III)). The mixture of 4 (20
mg, 0.03 mmol) and Cu(AcO)2‚2H2O (10 mg, 0.046 mmol) was
dissolved in 20 mL of freshly distilled THF. The resulting mixture
was refluxed for 30 min and evaporated to dryness with a vacuum
rotary evaporator. The remaining solid was dissolved in a small
volume of freshly distilled CH2Cl2 and filtered from an inorganic
salt. The reaction is quantitative and does not require recrystalli-
zation. UV-vis (CH2Cl2, λmax/nm (log ꢀ)): 433 (5.02), 506 (4.33),
compound
crystals grown by
6-Cu(II)
slow diffusion of methanol into
a CH2Cl2 solution
dark-green block
C50H34N4OCu
770.35
10.321(2)
23.474(5)
14.752(3)
97.608(15)
3542.6(12)
4
1.444
monoclinic
P21/c
1.240
crystal habit
formula
fw
a, Å
b, Å
c, Å
â, deg
V, Å3
Z
D
calc, g‚cm-3
cryst syst
space group
µ, mm-1
abs corrn
T, K
analytical (0.880/0.976)
100(2)
3.56 e θ e 70.78
-11 e h e 9, -29 e k e 23,
-15 e l e 18
θ range
hkl range
reflections
measd
unique, I g 2σ(I)
param/restraints
S
R1
wR2
26 953
6435
502/0
0.781
0.0474
0.1223
1
3
628 (4.24). H NMR (CDCl3, 298 K): δ 8.01 (d, 1H, J ) 4.9
Hz), 7.79-7.77 (m, 4H), 7.74 (m, 2H), 7.71 (d, 1H, 3J ) 4.6 Hz),
7.65 (d, 1H, 3J ) 4.9 Hz), 7.48-7.43 (m, 5H), 7.42-7.39 (m, 3H),
7.38-7.32 (m, 8H), 7.31 (bs, 1H), 6.53 (m, 1H), 5.98 (m, 1H),
5.79 (m, 1H), 2.53 (s, 3H), 2.52 (s, 3H). 13C NMR (CDCl3, 298 K,
partial data): δ 133.3, 133.0, 132.9, 131.0, 129.6, 129.0, 128.8,
128.4, 128.3, 127.7, 124.8, 87.2, 21.8.
3
(m, 2H), 7.51-7.46 (m, 9H), 7.44 (d, 2H, J ) 8.0 Hz), 7.39 (m,
1H), 7.35 (d, 2H, 3J ) 8.0 Hz), 7.25 (d, 1H, 3J ) 4.9 Hz), 6.92 (d,
1H, 3J ) 4.6 Hz), 6.72 (d, 1H, 3J ) 4.2 Hz), 6.70 (d, 1H, 3J ) 4.6
Hz), 6.69 (d, 1H, 3J ) 4.2 Hz), 6.59 (d, 1H, 3J ) 4.6 Hz), 6.54 (m,
1H), 6.15 (m, 1H), 5.95 (m, 1H), 2.45 (s, 3H), 2.44 (s, 3H). 13C
NMR (CDCl3, 298 K, partial data): δ 135.5 (C-13), 132.5 (C-5o),
132.4 (C-10o), 132.3 (C-12), 132.0 (C-20o), 131.8 (C-15o), 131.0,
128.9, 127.5 (C-5,20m,5p), 130.5 (C-8), 129.1 (C-7), 128.3 (C-
15m), 128.7 (C-10m), 127.9 (C-20p), 125.9 (C-5′), 123.3 (C-18),
122.1 (C-17), 119.2 (C-3′), 111.2 (C-4′), 21.8 (2C-p-Me). MS:
m/zcalc 724.2822 (calcd 724.2838 for C50H36N4O2).
5,20-Diphenyl-10,15-ditolyl-2-oxa-3-(2′-pyrrolyl)-21-carbap-
orphyrinatocopper(II) (6-Cu(II)). The mixture of 6 (13 mg, 0.018
mmol) and Cu(AcO)2‚2H2O (12 mg, 0.056 mmol) was dissolved
in 20 mL of freshly distilled THF. The resulting mixture was stirred
for 5 min and evaporated to dryness with a vacuum rotary
evaporator. The remaining solid was dissolved in a small volume
of freshly distilled CH2Cl2 and filtered from an inorganic salt. The
reaction is quantitative and does not require further purification.
UV-vis (CH2Cl2, λmax/nm (log ꢀ)): 363 (4.19), 402 (4.18), 487
(sh), 505 (4.60), 608 (3.71), 655 (4.30), 743 (3.60), 815 (3.60).
MS: m/zcalc 769.2154 (calcd 769.2128 for C50H36N4O63Cu).
5,20-Diphenyl-10,15-ditolyl-2-oxa-3-(2′-pyrrolyl)-21-hydroxy-
carbaporphyrinatocopper(II) (8). A total of 15 mg (0.27 mmol)
of KOH was dissolved in 20 mL of water and mixed with 30 mL
of H2O2 (30%). The resulting mixture was added to 6-Cu(II) (10
mg, 0.015 mmol) dissolved in 20 mL of freshly distilled CH2Cl2.
Whole mixture was stirred overnight and washed with water (2×).
The organic layer was passed through a chromatography column
with Al2O3 (base, GIV). A fast-moving orange band was collected
to give 8 with quantitative yield. UV-vis (CH2Cl2, λmax/nm (log
ꢀ)): 348 (sh), 384 (4.34), 515 (4.71), 613 (3.67), 667 (3.82), 880
(3.52), 959 (sh). HRMS: m/zcalc 785.2012 (calcd 785.1978 for
C50H34N4O263Cu).
Instrumentation. NMR spectra were recorded on a Bruker
Avance 500 spectrometer (frequencies: 1H NMR 500.13 MHz; 13
C
NMR 125.77 MHz) equipped with either a broad-band inverse-
gradient probehead or a direct broad-band probehead. Absorption
spectra were recorded on a diode-array Hewlett-Packard 8453
spectrometer. Mass spectra were recorded on an AD-604 spec-
trometer using the electrospray and liquid matrix secondary-ion
mass spectrometry techniques. EPR spectra were recorded on a
Bruker ESP 300 spectrometer operating with an X band equipped
with a ER 035M gaussmeter and a HP 53550B microwave
frequency counter. The spectra were simulated using the SYMFO-
NIA software package.
X-ray Analysis. X-ray-quality crystals of 6-Cu(II) were prepared
by diffusion of methanol into a dichloromethane solution contained
in a thin tube stored in a refrigerator. Data were collected at 100 K
on an Xcalibur PX k-geometry diffractometer, with Cu KR radiation
(λ ) 1.5418 Å). The data were corrected for Lorentz and
polarization effects. An analytical absorption correction was applied.
Crystal data are compiled in Table 2. The structure was solved by
a heavy-metal method with SHELXS-97 and refined by the full-
matrix least-squares method by using SHELXL-97 with anisotropic
thermal parameters for the non-H atoms. Scattering factors were
those incorporated in SHELXS-97.72,73
5,20-Diphenyl-10,15-ditolyl-2-oxa-3-(2′-pyrrolyl)-21-hydroxy-
porphyrin (9). 8 (10 mg, 0.013 mmol) was dissolved in 15 mL of
ethyl acetate. Then gaseous HCl was passed through the solution
to initiate a distinct color change from orange to violet. The resulting
mixture was chromatographed with Al2O3 (GIV) suspended in CH2-
Cl2. A fast-moving orange fraction was collected. The solvent was
removed with a vacuum rotary evaporator. Recrystallization with
CH2Cl2/hexane gave 9 in quantitative yield. UV-vis (CH2Cl2, λmax
/
nm (log ꢀ)): 381 (3.60), 500 (3.61). 1H NMR (CDCl3, 298 K): δ
(72) Sheldrick, G. M. SHELXL97, Program for Crystal Structure Solution;
11.49 (bs, NH), 8.87 (bs, OH), 7.84 (bs, NH), 7.61 (m, 2H), 7.57
University of Go¨ttingen: Go¨ttingen, Germany, 1997.
Inorganic Chemistry, Vol. 46, No. 16, 2007 6583

Pawlicki et al.
Supporting Information Available: Tables of crystal data,
bond lengths, angles, anisotropic thermal parameters (CIF files).
This material is available free of charge via the Internet at
http://pubs.acs.org.
Acknowledgment. Financial support from the Ministry
of Science and Higher Education (Grant 3 T09A 162 28) is
kindly acknowledged.
(73) Sheldrick, G. M. SHELXL97, Program for Crystal Structure Refine-
ment; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
IC700631T
6584 Inorganic Chemistry, Vol. 46, No. 16, 2007