Peculiar reactivity of face to face biscorrole and porphyrin - Corrole with a nickel(II) salt. X-ray structural characterization of a new nickel(II) bisoxocorrole

Article abstract of DOI:10.1039/b007623f

New nickel(II) bisoxocorrole complexes have been synthesized and characterized. Two nickel bisoxocorrole isomer complexes are formed in a 1:1 ratio when a biscorrole, where an anthracenyl bridge links the two macrocycles in a face to face arrangement, is

Full text of DOI:10.1039/b007623f

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Peculiar reactivity of face to face biscorrole and porphyrin–corrole
with a nickel(II) salt. X-Ray structural characterization of a new
nickel(II) bisoxocorrole
Francois Jerome,a Jean-Michel Barbe,a Claude P. Gros,a Roger Guilard,*a Jean Fischerb and
Raymond Weiss*b
a Universite de Bourgogne, L IMSAG UMR 5633, Faculte des Sciences Gabriel, 6, boulevard
Gabriel, 21100-Dijon, France. E-mail: rguilard=u-bourgogne.fr; Fax: (33) 0380396117
b Universite L ouis Pasteur, Institut L e Bel, 4, rue Blaise Pascal, 67000-Strasbourg, France.
E-mail: Ðscher=chimie.u-strasbg.fr; Fax: (33) 0388415363
Received (in Montpellier, France) 18th September 2000, Accepted 6th October 2000
First published as an Advance Article on the web 4th December 2000
New nickel(II) bisoxocorrole complexes have been synthesized and characterized. Two nickel bisoxocorrole isomer
complexes are formed in a 1 : 1 ratio when a biscorrole, where an anthracenyl bridge links the two macrocycles in a
face to face arrangement, is metallated by nickel in air. Evidence for the insertion of an oxo group at one of the
meso positions is given by the X-ray structural characterization of the Ni (BOCA) ““cisÏÏ isomer where BOCA is a
2
bisoxocorrole with an anthracenyl spacer. Conversely, under the same reaction conditions no nickel bisoxocorrole
is obtained when biphenylene is the linker of the biscorrole system, the major product of the reaction being a
bisnickel bisradical species. Only a small amount of a bisnickel hydrooxobiscorrole is isolated in this reaction. A
reaction mechanism for both series (anthracenyl and biphenylenyl) is given and a comparison of the behavior of the
biscorrole system with related derivatives is proposed.
““bisoxocorrolesÏÏ, similar to the oxophlorins observed in
porphyrin chemistry (Scheme 1).18h22
These bisoxocorroles are characterized by the presence of
an oxygen atom at one of the meso positions, precisely at the
C-15 and C-15@ or C-5@ positions (@ is given for the second
macrocycle). So far to our knowledge, this is the Ðrst example
Introduction
Numerous researches have been devoted to the molecular
structure, spectroscopy and electronic properties of metallo-
corroles.1h5 Although nickel complexes were among the Ðrst
metallocorroles reported,6 their structure was not clearly
deÐned for a long time.6h11 Indeed, until 1997, the structure of
of such a bismacrocycle ever described. The synthesis, the
the nickel corrole was uncertain due to its paramagnetic
X-ray characterization and 1H NMR studies of the nickel
nature.8,11h15 Furthermore, the low intensity of the Soret
bisoxocorrole Ni (BOCA) (BOCA is a bisoxocorrole with an
2
band led the authors to conclude that the corrole complex
was not totally aromatic and they postulated a nickel(II)
complex with an ““extraÏÏ hydrogen atom at one of the three
meso positions. In 1997 the electrochemistry data16 and a
crystal structure determination17 demonstrated that no such
hydrogen atom was present at this position. Conversely a dis-
torted square planar geometry indicated an interruption of the
corrole ring aromaticity. Magnetic measurements and the
unusual low intensity of the double band in the Soret region
of the electronic spectrum were in accordance with a radical
nature for the nickel complex.1,17 The authors pointed out
that the formal nickel(III) complex was in fact a nickel(II) one
with a delocalized electron in the p orbital of the ligand.
However, they assumed that the nickel(II) radical came from
the loss of an hydrogen radical from an intermediate nickel(II)
complex with a free imine not coordinated to the nickel.13
This intermediate was in equilibrium by an hydrogen radical
migration with a nickel(II) complex with an ““extraÏÏ hydrogen
atom at one of the meso positions.
anthracenyl spacer) as well as related derivatives are reported
in this article. A probable mechanism for this peculiar reaction
is given and reference is made to the di†erent behaviour of
monomeric nickel corroles.
Results
Synthesis
A standard procedure was employed to metallate the anthra-
cenyl bridged biscorrole 1 with nickel(II). The biscorrole was
heated at 80 ¡C in pyridine in the presence of an excess of
We recently reported the synthesis of four ““face to faceÏÏ
bismacrocycles containing either two corrole rings5 or a
porphyrin and a corrole unit,4 rigidly linked by two di†erent
bridges such as anthracenyl and biphenylenyl spacers. Here,
we show an interesting behaviour of these bismacrocycles
when metallated with a nickel salt. Indeed, the insertion of
nickel into these ““face to faceÏÏ bismacrocycles leads to the
formation of
a
novel family of macrocycles, named
Scheme 1
DOI: 10.1039/b007623f
New J. Chem., 2001, 25, 93È101
93
This journal is ( The Royal Society of Chemistry and the Centre National de la Recherche ScientiÐque 2001

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nickel(II) acetate under air, the metallation reaction being
monitored by UV-visible spectroscopy. After puriÐcation, the
1H NMR and mass spectrometry data led us to postulate the
formation of a nickel bisoxocorrole. In contrast to monomeric
corroles, the formation of radical species was not observed
and the isolated compounds were found diamagnetic indicat-
ing the presence of low spin nickel(II). The formation of two
bisoxocorrole isomers 2a and 2b occurred in 38% yield, the
oxygen atoms being either on the same side of the bismacro-
cycle (2a) or on opposite sides (2b) (Scheme 2).
The two bisoxocorrole isomers were easily separated by
column chromatography on silica gel. 2b was Ðrst collected
indicating that isomer 2b was less polar than 2a. Both isomers
were isolated in the same quantity (19% yield). Mass spec-
trometry measurements indicated a single ion at m/z 1688
([M]`~) for both derivatives in accordance with the presence
of two oxygen atoms on the bismacrocycle.
with a small amount of a mixed-ligand complex 5. Spectro-
scopic data of 5 were consistent with the presence of both
oxocorrole and hydrocorrole moieties. Mass spectrometry
analysis conÐrmed the probable structure of 5 with a peak at
m/z 1648 compared to 1632 for the bisradical 4 (Scheme 3).
Characterization of the nickel bisoxocorroles 2a and 2b
Nickel bisoxocorroles were characterized by 1H NMR, UV-
visible, infrared, mass spectrometry and by X-ray crystallog-
raphy.
During the metallation reaction, a typical change in the
UV-visible spectrum is observed (Table 1). A decrease in
intensity of the Soret band is noted which indicates a break-
down of the aromaticity in the macroring. For instance, the e
value for the Soret band of the anthracenyl biscorrole free
base 1 is 1.31 ] 105 whereas e is close to 0.80 ] 105 (dm3
mol~1 cm~1) for the nickel bisoxocorroles 2a and 2b. More-
over, the Soret band is extremely broad due to the super-
position of three bands between 379 and 416 nm. A single Q
band appears at 635 nm with a low e value of ca. 8.0 ] 103
Contrary to the anthracenyl derivative, using the same
metallation reaction conditions, the formation of a bisoxocor-
role was not observed in the case of the biphenylenyl deriv-
ative 3, the major product being the bisradical species 4 along
Scheme 2 Reagents and conditions: i, Ni(O CCH ) , 80 ¡C, pyridine, 3 h, 38%.
3 2
2
Scheme 3 Reagents and conditions: i, Ni(O CCH ) , 80 ¡C, pyridine, 3 h.
2
3 2
Table 1 UV-visible data of synthesized nickel(II) complexes and related derivatives
j
/nm (e/10~3 dm3 mol~1 cm~1)
max
Spacer
Compound
Solvent
CH Cl
Soret band
Q bands
È
Anthracenyl
1
È
È
È
416
(131.5)
417
(100.0)a
420
(100.0)a
391
(84.3)
394
(85.3)
È
È
È
È
572
(35.4)
582
608
(29.0)
605
2
2
7
Pyridine
524
(27.3)a
546
(26.5)a
È
(29.9)a
578
(33.3)a
È
7
CH Cl
2
2
2
2
2
2
(26.5)a
È
2a
CH Cl
379
(82.4)
380
(78.7)
402
(170.2)
È
411
(75.6)
416
(79.2)
È
635
(7.5)
635
(8.5)
È
2
2b
CH Cl
È
È
2
12
CH Cl
524
(30.1)
È
558
2
(34.2)
578
(39.5)
591
Biphenylenyl
3
CH Cl
404
(129.0)
420
(79.4)
417
(73.1)
386
(62.4)
383
(48.9)
È
È
È
607
(31.0)
614
2
4
Pyridine
È
È
517
(44.7)
543
(37.5)
È
(37.6)
571
(43.4)
È
4
CH Cl
2
2
2
2
(30.7)
È
5
CH Cl
350
(60.3)
358
420
(58.3)
479
672
(6.8)
653
2
È
Ni(TMEC)17 b
CH Cl
529
(3.2)
595
2
(62.2)
(5.4)
(3.3)
(11.0)
a Relative intensity. b TMEC \ 7,8,12,13,-tetraethyl-2,3,17,18-tetramethylcorrolato.
94
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Table 2 1H NMR chemical shifts of nickel(II) bisoxocorrole and hydrooxobiscorrole meso protons
d
H meso
Spacer
Compound
H-5
H-15
H-5@
H-15@
Anthracenyl
1
2a
2b
12
3
8.86
È
È
È
9.59
4.02(H-5 or 5@)
8.86
3.93
4.05
2.87
9.59
3.90(2H)
8.86
È
4.05
È
9.59
4.01(H-5 or 5@)
8.86
3.93
È
È
9.59
È
Biphenylenyl
5
Table 3 Selected bond lengths (A) and angles (¡) for compound 2a
dm3 mol~1 cm~1 (Fig. 1). It is noteworthy that the shape of
the UV-visible spectra of 2a and 2b is nearly identical to that
of the monomeric nickel corroles.
Ni1ÈN21
Ni1ÈN22
Ni1ÈN23
Ni1ÈN24
Ni2ÈN41
Ni2ÈN42
Ni2ÈN43
SN ÈC ÈC T
1.861(6)
1.880(6)
1.894(6)
1.859(6)
1.859(6)
1.873(6)
1.880(6)
109.3(9)
107.5(9)
106.8(9)
Ni2ÈN44
1.858(6)
1.871(13)
1.371(20)
1.431(25)
1.381(19)
1.417(36)
1.441(7)
123.8(9)
110.8(9)
SNiÈN T
2a and 2b are diamagnetic indicating the lack of any radical
species and the presence of a pure low spin nickel(II) complex.
1H NMR allows one to locate the oxygen atom since only one
proton is present at the meso positions. Moreover, the dis-
ruption of the macrocycle aromaticity decreases the ring
current and therefore the signal of the remaining meso proton
of the oxocorrole moiety appears around d 4 compared to 9
for the starting biscorrole 1 (See Table 2 for resonances of
meso protons and Experimental Section for d of other proton
sites). Furthermore, the 1H NMR spectra of 2a and 2b clearly
p
SN ÈC T
p
a
SC ÈC T
a
b
SC ÈC T
b
b
SC ÈC T
m
a
SC ÈC T
a
a
SC ÈC ÈC T
p
a
b
a
m
a
SC ÈN ÈC T
SN ÈC ÈC T
a a
a
p
b
p
SC ÈC ÈC T
a
b
b
rings linked directly via the C ÈC bond. Similar features have
a
a
show the dissymmetry of the molecule (absence of C
symmetry) which conÐrms the presence of only one oxygen
been observed previously in the structures of other metallocor-
2
roles.1,2 The average NiÈN bond distance in 2a is slightly
p
atom at one of the two available meso positions. For instance,
one signal is observed for the four methyl groups of the sym-
metric biscorrole 1 compared to two signals at d [0.22 and
[0.19 for those of the bisoxocorrole 2b.
longer than that of 1.844 A in the nickel(II) derivative of the
tetramethyltetraethylcorrole p-radical cation, NiII(TMEC~`),
in which the nickel(II) cation lies also in a distorted square-
planar environment.17 However, the NiÈN bond distances
p
present in Ni (BOCA) are shorter than the corresponding
2
Side- and top-views of the molecular structure of
Ni (BOCA) 2a are displayed in Fig. 2(a) and 2(b), respectively,
ones observed for the large number of reported structures of
2
with the labelling scheme used for all the non-hydrogen
nickel(II) porphyrins,23 the averages lying between 1.888 A in
Ni(TCHP) and 1.960 A in Ni(DeutDME) (TCHP \ tetra-
cyclohexylporphyrinate and DeutDME \ 2,4-diacetyldeutero-
porphyrinate dimethyl ester).23 This in 2a can be ascribed to
the reduced hole size of the two oxocorrole rings occurring in
[BOCA]4~ relative to the hole size of the porphyrin core. A
atoms. Fig. 3(a) and 3(b) show, respectively, in A ] 10~2 units
the perpendicular displacements of the nickel and the oxocor-
role core atoms relative to the oxocorrole mean planes. Fig. 4
illustrates the orientation and position of the mean planes of
the oxocorrole rings relative to that of the anthracenyl spacer.
Table 3 lists selected bond distances and angles as well as
some averages data for Ni (BOCA) É 2CH Cl É 2H O.
similar
decrease
of
the
MÈN
bond
lengths
p
is observed in several metallocorroles as di†erent as
[Rh(OMC)(AsPh )], [Co(OMTPC)(PPh )] and Mn(OMC)
(OMC \ 2,3,7,8,12,13,17,18-octamethylcorrolate; OMTPC \
2,3,7,8,12,13,17,18-octamethyl-5,10,15-triphenylcorrolate).24h26
As shown in Fig. 2(a) and 2(b), one oxygen atom is bonded
to a meso-carbon of each ring and only the cis isomer of
2
2
2
2
As shown in Fig. 2(a) and 2(b), both nickel atoms, Ni1 and
Ni2, lie in a four-coordinate distorted square-planar environ-
ment. The average Ni1ÈN and Ni2ÈN bond distances are
3
3
p
p
not signiÐcantly di†erent, their mean value being 1.871(6) A.
The shortest Ni1ÈN and Ni2ÈN bond distances, Ni1ÈN (24)
p
p
p
1.859(6) and Ni1ÈN (21) 1.861(6), Ni2ÈN (41) 1.859(5) and
Ni (BOCA) is present in the studied crystals. The two meso-
p
p
2
Ni2ÈN (44) 1.858(6) A, involve pyrrole nitrogens belonging to
positions occupied by an oxygen atom are C15 and C35
p
giving two cis C 2O groups oriented in the same direction.
m
The bond distances of 1.24(1) (C15ÈO1) and 1.26(1) A (C35È
O2) are in good agreement with expected C2O bond lengths.
C2O bond distances of similar values have been observed in
metallooxophlorin.27 The C ÈC bond distances adjacent to
a
m
the C 2O groups are not signiÐcantly di†erent. Their mean
m
value of 1.45(1) A is slightly longer than the mean value of the
four other C ÈC bond lengths of 1.40(1) A of the two rings
a
m
present in Ni (BOCA), but similar to the known distance for a
2
single C ÈC
bond (1.44 A). Moreover, both C2O groups
sp2 sp2
are not coplanar with the corrole mean planes, the dihedral
angles between the C14-C15(O1)-C16 and C34-C35(O2)-C36
mean planes and the oxocorrole mean planes of both rings
being 12.8(2) and 14.0(2)¡, respectively. These structural fea-
tures indicate that only a slight delocalization of the C2O
bond occurs across the p system of the corrole ring.
Although the core of the corrole p-cation radical ligand in
NiII(7,8-TMEC~`) is totally planar,17 the two rings of
Ni (BOCA) are slightly distorted. Both oxocorrole core con-
2
formations correspond to a mixture of irregular saddle and
Fig. 1 UV-visible spectra of H (BCA) and Ni (BOCA) species.
ruffle and doming distortions. The saddle distortions may be
6
2
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95

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Fig. 2 (a) Side- and (b) top-views of the molecular structure and atom numbering of Ni (BOCA). Thermal ellipsoids enclose 30% probability.
2
Hydrogen atoms are omitted for clarity.
characterized by the out of plane displacements of the geminal
b-pyrrole carbons of ]0.106(7) and [0.213(7) A for the Ni1-
and ]0.302(7) and [0.346(7) A for the Ni2-containing
macrocycles above and below the oxocorrole mean planes.
The doming of both rings may be described by the separation
relative to the oxocorrole mean plane of each ring, the corre-
sponding angles having values close to 0 (C2ÈC3), 3.8(2) (C7È
C8), 169.8(2) (C12ÈC13), 8.0(2) (C17ÈC18), 0(C22ÈC23),
176.9(2) (C27ÈC28), 3.3(2) (C32ÈC33) and 176.7(2)¡ (C37ÈC38).
The structure of Ni (BOCA) exhibits features similar to
2
between the 4N mean plane and oxocorrole mean plane of
those reported for the nickel(II) bisporphyrin complex
p
each ring of 0.050(1) and 0.108(1) A for the Ni1- and Ni2-
Ni (DPA) (DPA \ diporphyrin anthracene) with the same
2
containing macrocycles, respectively. The irregular ruffling
rigid anthracenyl bridge.28,29 The oxocorrole moieties in
may be characterized by the orientations of the C ÈC bonds
Ni (BOCA) are not stacked over one another, but are slightly
b
b
2
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Ni (DPA), the lateral shift is 2.40 A giving a NiÉ É ÉNi distance
2
of 4.566 A and an interring separation of 3.88 A.
The anthracenyl spacer is almost planar; the largest devi-
ation from its mean plane is 0.073(7) A (C80), the mean devi-
ation 0.041(7) A. The nickel(II) bisoxocorrole molecules,
Ni (BOCA), are stacked top to bottom in columns along the
2
[011] crystal direction. The shortest intermolecular contact
distances have values of 3.6 A.
Spectroscopic characterization of the nickel
hydrooxobiscorrole 5
The mixed-ligand nickel hydrooxobiscorrole complex 5 has
been characterized by 1H NMR (see Experimental section).
The meso methylene group of the hydrocorrole moiety is evi-
denced as a double doublet resonance at d 3.90. Two singlets
appear at d 4.01 and 4.02 corresponding to the single meso
protons of the hydrocorrole and oxocorrole macrocycles.
Likewise the lack of C symmetry is enhanced by the presence
2
of four di†erent signals around d 2.2 for the four methyl
groups of the bismacrocycle. Interestingly, and in contrast to
the anthracenyl derivative, only one isomer is detected by 1H
NMR. Hydrooxobiscorroles and bisoxocorroles have nearly
the same UV-visible spectra indicating loss of ring aromaticity
and a large Soret band centered at 386 nm is observed for 5
(Table 1).
Characterization of the bisradical species 7 and 4
In order better to understand the mechanism of formation of
these bisoxocorroles and hydrooxobiscorrole, the same metal-
lation reactions were carried out under an argon atmosphere
to evaluate the role of dioxygen in this reaction. Under the
same experimental conditions, but in the absence of dioxygen,
we could isolate the bisradical nickel complex 4 (biphenylenyl
spacer) and 7 (anthracenyl spacer) (Scheme 4). The UV-visible
spectra are di†erent from those described before for the bisox-
ocorrole, the hydrooxobiscorrole or the monomeric corrole
nickel complexes (see Table 1). For example, in pyridine, the
electronic absorption spectrum of 7 exhibits a Soret band at
417 nm and three Q bands at 524, 582 and 605 nm. A similar
UV-visible spectrum is observed for 4 (Soret band 420 nm; Q
bands 517, 591, 614 nm) (Table 1). Compound 7 is paramag-
netic and very broad signals are observed on the 1H NMR
spectrum between d [2 and 30 while for the biphenylenyl
derivative 4 broad signals appear between d 0 and 9. The ESR
spectrum of 7 shows a characteristic signal of a radical delo-
Fig. 3 Perpendicular displacements in A ] 10~2 units of (a) Ni1 and
the Ni1 oxocorrole-core atoms and (b) Ni2 and the Ni2 oxocorrole-
core atoms relative to the corresponding oxocorrole mean planes.
calized on the macrocycle and split into three lines (g \
slipped with respect to each other. A lateral shift of 1.535(2) A
occurs between Ni2 and the projection of Ni1 on the mean
plane of the oxocorrole ring containing Ni2 (Fig. 4). This
lateral shift leads to a NiÉ É ÉNi distance of 4.678(1) A and a slip
angle of 19.1(6)¡. The distance between a virtual plane con-
taining the meso-carbon C15 which is parallel to the mean
plane of the Ni2 oxocorrole is 4.419(2) A. The dihedral angle
of this virtual plane and the mean plane of the Ni1 oxocorrole
is 7.8(3)¡ (Fig. 4). In the case of the Pacman porphyrin,
1
2.004, g \ 2.007, g \ 2.017) at 100 K as observed for mono-
2
3
meric nickel corroles.16,17 The ESR spectrum of 4 exhibits a
very low intensity signal in the same region as for 7, thus indi-
cating a stronger interaction between the two radicals in 4
than in 7. ESR and 1H NMR are together in accordance with
the formulation as a nickel(II) bisradical for derivatives 4 and
7. Additional evidence supporting this hypothesis comes
directly from the mass spectrum exhibiting a single ion at m/z
1658 for 7 and 1632 for 4. It should be noted that the bisradi-
cal species 7 is very unstable under dioxygen or air and
decomposition occurs under these conditions only after a few
minutes. Conversely, 4 is more stable and no extensive decom-
position is observed after three days in solution. The direct
oxygenation of these bisradical species does not lead to the
formation of bisoxocorroles or mixed hydrooxobiscorroles
respectively. This indicates that the bisradicals 4 and 7 are not
the intermediates in the oxocorrole formation.
Synthesis and characterization of the bisnickel porphyrin
oxocorrole derivative 12
In order to dismiss an eventual chemical cooperativity
between the two corrole macrocycles during the reaction, the
Fig. 4 Orientation and position of the oxocorrole ring mean planes
relative to the anthracenyl spacer.
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Scheme 4 Reagents and conditions: i, Ni(O CCH ) , pyridine; ii, H~ migration to a dioxygen molecule; iii, radical coupling; iv, [H O; v, argon
2
3 2
2
atmosphere; vi, isomerization; vii, O . (For clarity, the mechanism for only half of the molecule in shown.)
2
porphyrinÈcorrole bismacrocycle 10 was metallated by a
nickel salt. After three hours of reaction in pyridine under
reÑux only the corrole macrocycle was metallated as shown
by mass spectrometry. Attempts to isolate this mono-
metallated complex 11 were unsuccessful due to an extensive
decomposition during the puriÐcation. This complex was only
identiÐed in the reaction medium by mass spectrometry by the
presence of one peak at m/z 1353 corresponding to a nickel(II)
oxocorrole face to face to a porphyrin free base. Taking into
account the higher e value for the porphyrin ring compared to
corrole and oxocorrole ones, the nickel(II) oxocorroleÈ
porphyrin free base 11 exhibits the same UV-visible spectrum
as that of the starting porphyrinÈcorrole 10. Metallation of
the porphyrin ring only occurs in benzonitrile under reÑux
leading to the formation of the bisnickel(II) derivative 12
(Scheme 5).
ecule is chiral and therefore two stereoisomers are formed
during ring oxidation of the corrole.
Discussion
Proposed mechanism for formation of the bisoxocorroles
2a and 2b
From the results described, the characterization of the hydro-
oxobiscorrole 5, the di†erence in stability of the two bisradical
species 4 and 7 in air, and the mechanism for metallation of
corroles by nickel proposed in the literature, we can suggest a
mechanism which corresponds to the physicochemical data
obtained. A concerted mechanism implying a dioxygen mol-
ecule attack and a hydrogen radical migration from the imine
to the meso position is proposed in Scheme 4.
The mass spectrum of complex 12 consists in a single peak
at m/z 1410 and the 1H NMR spectrum reveals the total dis-
symmetry. The meso proton of the oxocorrole moiety is
shifted downÐeld (d \ 2.87) compared to that of the bisoxo-
corrole 2a or 2b (d B 4) or the biscorrole (d B 9) (see Table 2
and Experimental section). This results from the superposition
of two phenomena. First, as in the case of bisoxocorroles, the
ring current is lower than for monocorroles and therefore the
signal appears downÐeld. Secondly, the addition of the strong
ring current of the porphyrin over the oxocorrole moiety
shifts this signal more downÐeld. It is interesting that this mol-
The Ðrst step is analogous to that described in the literature
for the monomeric corrole series; it consists in the formation
of a bisnickel(II) biscorrole 6 with one imine group of each
corrole ring not co-ordinated. Under a dioxygen atmosphere,
the migration of the hydrogen radical from the remaining
imine group to the meso position concerted with a dioxygen
molecule attack (8) generates the transient bishydroperoxide
9a. This unstable intermediate immediately loses two water
molecules to give the corresponding bisoxocorrole 2a. This
mechanism perfectly explains the formation of only one oxo
group per corrole ring. The formation of the bisoxocorrole is
Scheme 5 Reagents and conditions: i, Ni(O CCH ) , reÑux, pyridine, 3 h; ii, Ni(O CCH ) , reÑux, PhCN, 1 h.
3 2 3 2
2
2
98
New J. Chem., 2001, 25, 93È101

View Article Online
only due to a radical species generated by insertion of the
nickel into the cavity of the corrole. The access to isomer 2b
can be explained by the same mechanism if one takes into
account the possible delocalization of the radical on the
second meso position of 6.
Moleculaire de lÏUniversite de BourgogneÏÏ, chemical shifts are
expressed in ppm relative to chloroform (7.258 ppm). Micro-
analyses were performed at the Universite de Bourgogne on a
Fisons EA 1108 CHNS instrument. Mass spectra were
obtained on Bruker ProFLEX III MALDI/TOF (matrix
assisted laser desorption ionization time of Ñight) spectro-
meter mode using dithranol as matrix. X-Ray di†raction data
were collected on a Enraf-Nonius Kappa-CCD di†ractometer
(Mo-Ka radiation, j \ 0.710 73 A).
Proposed mechanism for the formation of complexes 4 and 5
A radical interaction can account for the di†erence in reacti-
vity of compounds 1 and 3. As described for ““PacmanÏÏ
porphyrins30h36 or biscorroles5 and porphyrinÈcorroles,4 the
spacer length (anthracenyl or biphenylenyl) is of major impor-
tance in the reactivity of the complex formed. For the anthra-
cenyl derivative the two corrole rings behave as independent
macrocycles since no interaction occurs due to the length of
the bridge (4.9 A). For the biphenylenyl analogue the shorter
distance between the two corrole rings (3.8 A) leads to a
stronger interaction between the two macrocycles. Therefore,
the major formation of the bisradical species 4 is observed and
the hydrooxobiscorrole 5 is produced as a minor compound.
Furthermore, no bisoxocorrole derivative, which is the main
product in compound 1 metallation by nickel, is formed. The
strong interaction between the two radicals in 4 is demon-
strated by the 1H NMR spectrum which exhibits signals in a
diamagnetic region. However, the spacer is not short enough
to observe a complete antiferromagnetic coupling between the
two radicals and this can explain the broadness of the NMR
signals. The formation in low yield of only one hydro-
oxobiscorrole isomer follows from this interaction. Con-
versely, for the anthracenyl compound, the distance between
the two corrole rings is too large to observe a spin interaction
between the two radicals and each radical is delocalized on
each meso position and statistically the two isomers 2a and 2b
are generated in the same amount.
It is worth pointing out that a monomeric corrole bearing a
phenyl group at the C-10 position does not a†ord the
nickel(II) oxocorrole but the nickel(II) radical. The formation
of oxocorroles is observed only in the case of face to face bis-
macrocycles. This probably stems from a larger electron
density at the meso position than at other carbon atoms, com-
pared to the monomeric corroles, resulting from the super-
position of the two corrole rings. Molecular modeling
calculations currently underway will probably answer this
question.
Finally, infrared spectra of all the derivatives were recorded
and typical values for the carbonyl group stretching bands of
bisoxocorroles were found. As in the case of oxophlorins
(1560È1580 cm~1)22 or dipyrroketones, the carbonyl vibration
frequencies arise around 1600 cm~1 (see Experimental
section). This low value for a carbonyl group vibration indi-
cates a certain degree of polarization of the C2O bond. In
comparison with metallated oxophlorins, a weaker polariza-
tion is found for the carbonyl group of the oxocorrole which
seems to indicate a stronger delocalization of the C2O group
of the oxophlorins than that of the oxocorrole.22
Chemicals
For all syntheses, chemicals were commercially available and
used without further puriÐcation. Syntheses of face to face
biscorroles and porphyrinÈcorroles were performed using a
previously described procedure.4,5
Syntheses
Complexes 2a and 2b. A suspension of 100 mg (0.06 mmol)
of compound 1 and 80 mg (0.30 mmol) of nickel(II) acetate in
50 ml of pyridine was heated to 80 ¡C for three hours in the
dark with stirring then the solvent was evaporated under
vacuum. The solid was dissolved in dichloromethane and
chromatographed on silica gel. The isomer 2b was Ðrst col-
lected using CH Cl Èheptane (6 : 4) as eluent and 2a with
2
2
neat CH Cl as eluent. Both isomers were crystallized from
2
2
CH Cl ÈCH OH (1 : 2) to give black crystals (2a: 20.7 mg,
2
2
3
19% 2b: 20.7 mg, 19%). 2a: 1H NMR (200 MHz, CDCl ,
3
25 ¡C) d [0.29 (s, 6H, CH ), [0.13 (s, 6H, CH ), 0.36 (t, 6H,
3
2
3
CH CH ), 0.46 (t, 6H, CH CH ), 1.56 (m, 8H, CH CH ), 3.93
2
3
3
2
3
(s, 2H, meso-CH), 6.13È7.83 (m, 46H, Ph, anthracene), 8.23 (s,
1H, anthracene) and 8.63 (s, 1H, anthracene); MS (MALDI/
TOF) m/z \ 1688 ([M]`~); IR (KBr) v \ 2960 (CH), 2930
(CH), 2857 (CH) and 1633 cm~1 (CO); Calc. for
C
H
N Ni O É (CH OH) C 78.85, H 5.04, N 6.51; found
112 82
8
2
2
3
C 78.72, H 4.99, N 6.63%. 2b: 1H NMR (200 MHz, CDCl ,
3
25 ¡C) d [0.22 (s, 6H, CH ), [0.19 (s, 6H, CH ), 0.31 (t, 6H,
3
2
3
CH CH ), 0.39 (t, 6H, CH CH ), 1.48 (m, 8H, CH CH ), 4.05
2
3
3
2
3
(s, 2H, meso-CH), 6.08È7.81 (m, 46H, Ph, anthracene), 8.21 (s,
1H, anthracene) and 8.83 (s, 1H, anthracene); MS (MALDI/
TOF) m/z \ 1688 ([M]`~); IR (KBr) v \ 2956 (CH), 2930
(CH), 2860 (CH) and 1631 cm~1 (CO); calc. for
C
H
N Ni O É CH OH. C 78.85, H 5.04, N 6.51; found C
112 82
8
2
2
3
79.05, H 4.95, N 6.47%.
Complex 4. A suspension of 100 mg (0.06 mmol) of com-
pound 3 and 80 mg (0.30 mmol) of nickel(II) acetate was
heated at 80 ¡C in 50 ml of pyridine under argon and stirred at
this temperature for three hours in the dark. The solvent was
evaporated and the solid dried under vacuum. The solid was
dissolved in deoxygenated dichloromethane and chromato-
graphed on silica gel under argon. The product was Ðrst col-
lected with CH Cl as eluent to give black crystals in 49%
2
2
yield (47.9 mg) by slow evaporation of the solvent. MS
(MALDI/TOF): ([M]`~). Calc. for
N Ni É H O: C 80.01, H 5.13, N 6.79. Found: C
m/z \ 1632
Experimental
C
H
110 82
8
2
2
79.89, H 5.24, N 6.86%.
Instrumentation
IR spectra were recorded on a Bruker IFS 66v FTIR spectro-
photometer for samples prepared as 1% dispersions in KBr
pellets, UV-visible spectra on a Varian Cary 5 spectrophotom-
eter. EPR measurements were performed on a Bruker ESP
300 instrument at 100 K in toluene. The g values were
Complex 5. This was prepared in 12% yield (13.0 mg), as
described above for complexes 2a and 2b, starting from com-
pound 3. 1H NMR (200 MHz, CDCl , 25 ¡C): d 0.83 (t, 6H,
3
CH CH ), 0.85 (t, 6H, CH CH ), 2.09 (s, 6H, CH ), 2.18 (s,
2
3
2
3
3
6H, CH ), 2.22 (s, 6H, CH ), 2.29 (s, 6H, CH ), 3.90 (dd, 2H,
meso-CH ), 4.01 (s, 1H, meso-CH), 4.02 (s, 1H, meso-CH), 6.98
(m, 15H, Ph, biphenylene), 7.08 (m, 14H, Ph, biphenylene) and
3
3
3
measured
relative
to
diphenylpicrylhydrazyl
(dpph)
2
(g \ 2.0037 ^ 0.002). Basic alumina (Merck; usually Brock-
mann Grade III, i.e. deactivated with 6% water) and silica gel
(Merck; 70È120 lm) were used for column chromatography.
1H NMR spectra were recorded on a Bruker AC 200 Fourier
transform spectrometer of the ““Centre de Spectrometrie
7.21 (m, 17H). MS (MALDI/TOF): m/z \ 1648 ([M]`~). IR
(KBr): v \ 3068 (CH), 3034 (CH), 2961 (CH), 2925 (CH), 2852
(CH) and 1624 cm~1 (CO) Calc. for C
H
N NiO: C 80.11,
55 41
4
H 5.01, N 6.79. Found: C 79.93, H 5.11, N 6.83%.
New J. Chem., 2001, 25, 93È101
99

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Table 4 X-Ray experimental data for complex 2a
Acknowledgements
Formula
Molecular weight
Crystal system
Space group
C
H
N Ni O É 2CH Cl É 2H O
We are grateful to the French Ministry of Research (MENRT)
and CNRS (UMR 5633) for Ðnancial support. The ““Region
BourgogneÏÏ and ““Air LiquideÏÏ are acknowledged for scholar-
ships (FJ). The authors are also grateful to M. Soustelle for
assistance in the synthesis of pyrrole precursors.
112 82
8
2
2
2
2
2
1895.27
Triclinic
P1
a/A
b/A
c/A
a/¡
16.1351(7)
16.3746(6)
19.6653(7)
109.763(3)
93.411(3)
90.830(3)
4877.7(7)
2
0.554
173
37 354
8937
b/¡
c/¡
References
U/A
Ž
3
1
C. Erben, S. Will and K. M. Kadish, in T he Porphyrin Handbook,
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Z
k/mm~1
T /K
2
R. Paolesse, in T he Porphyrin Handbook, eds. K. M. Kadish,
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Number of data measured
Number of data with
I [ 3p(I)
3
4
5
C. Tardieux, C. P. Gros and R. Guilard, J. Heterocycl. Chem.,
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R
0.073
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w
6
7
A. W. Johnson and I. T. Kay, J. Chem. Soc., 1965, 1620.
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described above for complex 4, starting from compound 1.
MS (MALDI/TOF): m/z \ 1658 ([M]`~). Calc. for
8
9
C
H
N Ni: C 81.07, H 5.10, N 6.75. Found: C 81.22, H
56 42
4
5.31, N 6.62%.
10 R. Grigg, A. W. Johnson and G. Shelton, J. Chem. Soc. C, 1971,
2287.
Complex 12. A solution of 150 mg (0.12 mmol) of com-
pound 10 and 145 mg (0.58 mmol) of nickel(II) acetate was
reÑuxed in benzonitrile for 1.5 hour. The solvent was evapo-
rated under vacuum and the solid chromatographed on silica
gel using CH Cl Èheptane (6 : 4) as eluent. The crude product
11 N. S. Hush, J. M. Dyke, M. L. Williams and I. S. Woolsey, J.
Chem. Soc., Dalton T rans., 1974, 395.
12 A. W. Johnson, in Porphyrins and Metalloporphyrins, ed. K. M.
Smith, Elsevier, Amsterdam, 1975, p. 729.
2
2
was crystallized from a CH Cl ÈCH OH mixture to give
13 R. Grigg, in T he Porphyrins, ed. D. Dolphin, Academic Press,
2
2
3
New York, 1978, vol. 2, p. 327.
complex 12 in 12% yield (16.5 mg). 1H NMR (200 MHz,
14 N. S. Hush and M. L. Dyke, J. Inorg. Nucl. Chem., 1973, 35,
4341.
CDCl , 25 ¡C): d [0.48 (s, 3H, CH ), [0.42 (s, 3H, CH ),
1.24 (s, 3H, CH ), 1.43 (s, 3H, CH ), 1.55 (s, 3H, CH ), 1.59 (t,
3H, CH CH ), 1.76 (t, 3H, CH CH ), 2.06 (s, 3H, CH ), 2.87
(s, 1H, meso-CH), 2.96 (s, 3H, CH ), 3.27 (s, 3H, CH ), 3.57 (s,
3
3
3
15 H. R. Harrison, O. J. R. Hodder and D. Crowfoot Hodgkin, J.
3
3
3
Chem. Soc. B, 1971, 640.
2
3
2
3
3
16 K. M. Kadish, V. A. Adamian, E. Van Caemelbecke, E. Gueletii,
S. Will, C. Erben and E. Vogel, J. Am. Chem. Soc., 1998, 120,
11986.
3
3
3
3H, CH ), 3.67 (s, 3H, CH ), 3.69 (m, 4H, CH CH ), 4.69 (d,
3
3
2
1H, anthracene), 5.61 (d, 1H, anthracene), 5.84 (d, 1H,
anthracene), 6.32 (m, 12H, Ph), 6.49È6.67 (m, 16H, Ph), 6.96
(m, 12H, Ph), 7.79È7.96 (m, 2H, anthracene), 8.38 (d, 1H,
anthracene), 8.53 (s, 1H, anthracene), 8.65 (s, 1H, anthracene),
9.49 (s, 1H, meso-CH), 9.60 (s, 1H, meso-CH) and 11.92 (s, 1H,
meso-CH). MS (MALDI/TOF): m/z \ 1410 ([M]`~). IR
(KBr): v \ 2962 (CH), 2926 (CH), 2861 (CH) and 1621 cm~1
17 S. Will, J. Lex, E. Vogel, H. Schmickler, J. P. Gisselbrecht, C.
Haubtmann, M. Bernard and M. Gross, Angew. Chem., Int. Ed.
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19 R. G. Khoury, L. Jaquinod, A. M. Shachter, N. Y. Nelson and
K. M. Smith, Chem. Commun., 1997, 215.
20 R. G. Khoury, L. Jaquinod, R. Paolesse and K. M. Smith, T etra-
hedron, 1999, 55, 6713.
(CO). Calc. for C
H
N Ni O É (H O): C 76.49, H 5.22, N
91 72
8
2
2
7.84. Found: C 76.25, H 5.43, N 7.23%.
21 R. G. Khoury, L. Jaquinod, D. J. Nurco, R. K. Pandey, M. O.
Senge and K. M. Smith, Angew. Chem., Int. Ed. Engl., 1996, 35,
2496.
Crystal structure determination of complex 2a
Suitable single crystals of Ni (BOCA) É 2CH Cl É 2H O 2a
22 P. S. Clezy, in T he Porphyrins, ed. D. Dolphin, Academic Press,
2
2
2
2
New York, 1978, vol. 2, p. 103.
were obtained by slow evaporation of a dichloromethaneÈ
methanol solution at room temperature. All experimental
parameters used are given in Table 4. For all subsequent cal-
culations the Enraf-Nonius OpenMoleN package was used.37
The structure was solved using direct methods. Hydrogen
atoms were introduced as Ðxed contributors in structure
factor calculations by their computed coordinates (CÈH 0.95
A) and isotropic thermal parameters such as B(H) \ 1.3
23 W. R. Scheidt, in T he Porphyrin Handbook, eds. K. M. Kadish,
K. M. Smith and R. Guilard, Academic Press, New York, 2000,
vol. 3, p. 49.
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1990, 463.
26 S. Licoccia, E. Morgante, R. Paolesse, F. Polizio, M. O. Senge, E.
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27 A. L. Balch, Coord. Chem. Rev., 2000, 200–202, 349.
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29 J. P. Fillers, K. G. Ravichandran, I. Abdalmuhdi, A. Tulinsky
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1992, 114, 9877.
B
(C) A
eqv
omitted. One of the CH Cl and one of the water molecules
Ž 2 but not reÐned. Water and CH Cl protons were
2
2
2
2
are disordered over 2 sites in the ratio 1 : 1. Full least-squares
reÐnements on F. A Ðnal di†erence map revealed no signiÐ-
cant maxima. The scattering factor coefficients and anomalous
dispersion coefficients come respectively from Tables 2.2b and
2.3.1 of ref. 38.
CCDC reference number 440/223. See http://www.rsc.org/
suppdata/nj/b0/b007623f/ for crystallographic Ðles in .cif
format.
100
New J. Chem., 2001, 25, 93È101

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32 R. Guilard, S. Brandes, A. Tabard, N. Bouhmaida, C. Lecomte,
P. Richard and J. M. Latour, J. Am. Chem. Soc., 1994, 116, 10202.
33 J. P. Collman, P. S. Wagenknecht, J. E. Hutchison, N. S. Lewis,
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Mishra, J. Am. Chem. Soc., 1993, 115, 4947.
36 J.-M. Barbe and R. Guilard, in T he Porphyrin Handbook, eds.
K. M. Kadish, K. M. Smith and R. Guilard, Academic Press,
New York, 2000, vol. 2, p. 211.
37 OpenMoleN, Interactive Structure Solution, Nonius B. V., Delft,
1997.
34 J. P. Collman, Y. Y. Ha, P. S. Wagenknecht, M. A. Lopez and R.
Guilard, J. Am. Chem. Soc., 1993, 115, 9080.
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35 J. P. Collman, Y. Y. Ha, R. Guilard and M. A. Lopez, Inorg.
Chem., 1993, 32, 1788.
New J. Chem., 2001, 25, 93È101
101