Synthesis and structure of [meso-triarylcorrolato]silver(III)

Article abstract of DOI:10.1021/ic0261171

An efficient meso-triarylcorrole synthesis is detailed, and the formation and spectroscopic properties of their diamagnetic square-planar d⁸ AG(III) complexes are described. The spectroscopic properties of the [corrolato]-AG(III) complexes are contrasted with those of the corresponding [porphyrinato] Ag(II) complexes. The oxidation state of the central metal in the corrolato complexes was inferred from their diamagnetic NMR spectra, from X-ray photoelectron spectroscopy measurements, and by single-crystal X-ray diffractometry of the [meso-tetra-p-tolylcorrolato]-silver(III) complex TTCAg^III, as its toluene solvate (crystal data for C₄₀H₂₉N₄Ag·C₇ H₈: monoclinic space group C2/c with a = 21.4679(19) A, b = 20.7606(19) A, c = 16.0122(11) A, β = 93.700(4)°, V = 7121.5(10) A³, Z = 8, R = 0.0453, and R_w = 0.1131). The conformation of the corrolato ligand in the complex is slightly saddled. The AG(III) complexes are without precedent in the coordination chemistry of corroles. The Ag(III) complexes underline the ability of meso-triarylcorroles to stabilize higher oxidation states as compared to the corresponding mesotetraarylporphyrinato complexes.

Full text of DOI:10.1021/ic0261171

Inorg. Chem. 2003, 42, 1673−1680
Synthesis and Structure of [meso-Triarylcorrolato]silver(III)
,†
Christian Bru1ckner,* Cheri A. Barta,†,‡ Raymond P. Brin˜as,† and Jeanette A. Krause Bauer§
Department of Chemistry, Unit 3060, UniVersity of Connecticut, Storrs, Connecticut 06269-3060,
and Department of Chemistry Crystallographic Facility, UniVersity of Cincinnati,
P.O. Box 210172, Cincinnati, Ohio 45221-0172
Received October 17, 2002
An efficient meso-triarylcorrole synthesis is detailed, and the formation and spectroscopic properties of their
diamagnetic square-planar d8 Ag(III) complexes are described. The spectroscopic properties of the [corrolato]-
Ag(III) complexes are contrasted with those of the corresponding [porphyrinato]Ag(II) complexes. The oxidation
state of the central metal in the corrolato complexes was inferred from their diamagnetic NMR spectra, from X-ray
photoelectron spectroscopy measurements, and by single-crystal X-ray diffractometry of the [meso-tetra-p-tolylcorrolato]-
III
silver(III) complex TTCAg , as its toluene solvate (crystal data for C H N Ag‚C H : monoclinic space group C2/c
40 29
4
7 8
3
with a ) 21.4679(19) Å, b ) 20.7606(19) Å, c ) 16.0122(11) Å, â ) 93.700(4)°, V ) 7121.5(10) Å , Z ) 8, R
) 0.0453, and Rw ) 0.1131). The conformation of the corrolato ligand in the complex is slightly saddled. The
Ag(III) complexes are without precedent in the coordination chemistry of corroles. The Ag(III) complexes underline
the ability of meso-triarylcorroles to stabilize higher oxidation states as compared to the corresponding meso-
tetraarylporphyrinato complexes.
Introduction
Corroles are tetrapyrrolic fully conjugated macrocycles
containing three methine bridges and one direct pyrrole-
pyrrole linkage (Figure 1).1 Both porphyrins and corroles
contain 18 π-electron systems with two or one “cross-
conjugated” â,â′-double bonds, respectively. The 18 π-sys-
tem in the contracted framework of corroles is maintained
by change of the oxidation state of one nitrogen. Three pyr-
role-type nitrogens and one imine-type nitrogen thus line the
central cavity of corroles as compared to two nitrogens of
each type in porphyrins. These structural differences are
reflected in the altered metal coordination properties of these
square-planar tetradentate ligands: the smaller trianionic
corrolato ligand has a greater ability to stabilize higher central
metal oxidation states than the larger dianionic porphyrinato
ligand.2-9 For instance, the stable oxidation states of manga-
nese and iron in their porphyrinato complexes are +III, while
in their corrolato complexes they are +IV.3,7,8
Figure 1. Chromophore structure of porphyrins and corroles, highlighting
their 18π-electron systems.
The synthesis of â-octaalkylcorroles is nontrivial.1 How-
ever, the discovery by Gross and co-workers that meso-
triarylcorroles can be readily synthesized in one step from
electron-poor aldehydes and pyrrole rejuvenated the field of
corrole coordination chemistry.9-12 Some of the interest arises
(2) Licoccia, S.; Paolesse, R. Struct. Bonding (Berlin) 1995, 84, 71-133.
(3) Vogel, E.; Will, S.; Tilling, A. S.; Neumann, L.; Lex, J.; Bill, E.;
Trautwein, A. X.; Wieghardt, K. Angew. Chem., Int. Ed. Engl. 1994,
33, 731-735.
(4) Will, S.; Lex, J.; Vogel, E.; Schmickler, H.; Gisselbrecht, J.-P.;
Haubtmann, C.; Bernard, M.; Gross, M. Angew. Chem., Int. Ed. Engl.
1997, 36, 357-361.
(5) Ghosh, A.; Wondimagegn, T.; Parusel, A. B. J. J. Am. Chem. Soc.
2000, 122, 5100-5104.
(6) Ghosh, A.; Steene, E. J. Biol. Inorg. Chem. 2001, 6, 740-751.
(7) Golubkov, G.; Bendix, J.; Gray, H. B.; Mahammed, A.; Goldberg, I.;
DiBilio, A. J.; Gross, Z. Angew. Chem., Int. Ed. 2001, 40, 2132-
2134.
* To whom correspondence should be addressed. Phone: (860) 486-
2743. Fax: (860) 486-2981. E-mail: c.bruckner@uconn.edu.
† University of Connecticut.
‡ Current address: Department of Chemistry, University of British
Columbia, Vancouver V6T 1Z1, Canada.
§ University of Cincinnati.
(1) Paolesse, R. In The Porphyrin Handbook; Kadish, K. M., Smith, K.
M., Guilard, R., Eds.; Academic Press: San Diego, 2000; Vol. 2, pp
201-300.
(8) Gross, Z. J. Biol. Inorg. Chem. 2001, 6, 733-738.
(9) Wasbotten, I. H.; Wondimagegn, T.; Ghosh, A. J. Am. Chem. Soc.
2002, 124, 8104-8116.
10.1021/ic0261171 CCC: $25.00 © 2003 American Chemical Society
Published on Web 02/05/2003
Inorganic Chemistry, Vol. 42, No. 5, 2003 1673

Bru1ckner et al.
Table 1. XPS Binding Energies (eV) of Free Base Corrole TTCH3 and
from the catalytic activity of meso-triarylcorrolato chromium,
manganese, and iron complexes in epoxidation, hydroxyla-
tion, and cyclopropanation reactions, a reactivity correlated
with the ability of the ligand to stabilize high metal oxidation
states.13-18 Since the initial meso-triarylcorrole syntheses, we
and others reported a number of improved, more general or
complementary methodologies.9,12,19-26
On the basis of our earlier communication,23 we detail here
an efficient synthesis of meso-triphenyl- (TPCH3) and meso-
tri-p-tolylcorrole (TTCH3). Further, we will report the sil-
ver complexes of meso-triarylcorroles. To the best of our
knowledge, no examples of silver corrolato complexes were
reported to date.27 The stable oxidation state of silver in
porphyrinato complexes is d9 Ag(II).28,29 In contrast, we will
demonstrate here using a variety of spectroscopic methods
and single-crystal X-ray diffractometry that the stable oxida-
tion state of silver corrolato complexes is +III. The structural
determination will also furnish the first structurally character-
ized corrolato metal complex exhibiting a saddled macrocycle
conformation.
its Silver Complex TTCAgIII in Comparison with Literature Dataa
Ag 3d3/2
Ag 3d5/2
C 1s
N 1s
ref
TPPH2
TTCH3
TPPAgII
b
b
284.5
399.4
397.3
57
b
b
284.44c 399.59 this work
397.69
284.3
284.2
373.7
367.6
371.0
371.70
398.3
398.7
58
58
[TPPAgIII](ClO4) 377.1
TTCAgIII
377.66
284.70 398.94 this work
(376.83)d (370.86)d
a For the complete data set of the XPS analyses see Supporting
Information. b Not applicable. c The sp3 carbon signal expected for the
p-methyl groups cannot be distinguished from adventitious carbons signals.
d The shoulders in the Ag 3d3/2 and 3d5/2 peak regions (see Figure 4) could
be modeled assuming two species with the binding energies listed (for the
details of the curve fitting see Supporting Information). The observation of
two species is reproducible though their relative ratios varied from sample
to sample. We thus assume the origin of the two Ag species to be a crys-
talline and an amorphous phase formed during the film deposition by evap-
oration of a dilute benzene solution of the substrates onto the silicon wafer.
µm; preparative TLC plates (500 µm silica gel on glass) and the
flash column silica gel (standard grade, 60 Å, 32-63 µm) used
were provided by Sorbent Technologies, Atlanta, GA. The use of
a Varian Chroma..Zone flash chromatography system proved to
be advantageous for the rapid chromatographic separation of
synthetic intermediates and final products. 1H and 13C NMR spectra
were recorded on a Bruker DRX400. The NMR spectra are
expressed on the δ scale and were referenced to residual solvent
peaks. UV-vis spectra were recorded on a Cary 50 spectro-
photometer and IR spectra on a Perkin-Elmer Model 834 FT-IR.
ESI mass spectra were recorded on a Micromass Quattro II. High-
resolution FAB mass spectra were provided by the Mass Spec-
trometry Facility, Department of Chemistry and Biochemistry,
University of Notre Dame (Bill Boggess). Elemental analyses were
provided by Numega Resonance Labs Inc., San Diego, CA.
X-ray Photoelectron Spectroscopy. XPS analyses were carried
out on a Leybold-Heraeus model 3000 spectrometer upgraded with
a SPECS EA10MCD energy analyzer. Samples were prepared by
evaporation of a benzene solution of the corroles onto a silicon
wafer. Samples did not show any sign of charging as evidenced by
the reproducibility of the data and the position of the C 1s and N
1s peaks. The XPS data are summarized in Table 1.
X-ray Crystallography.32 Single crystals of TTCAgIII‚C7H8 were
obtained by slow evaporation of a toluene solution. A crystal of
the approximate dimensions 0.015 × 0.010 × 0.010 mm was
mounted on the tip of a loop with paratone-N and bathed in a cold
stream. The intensity data were collected on a Kappa goniostat (2θ
) 5°, others ) 0°) with a SMART6000 CCD detector at
ChemMatCARS Sector 15 (Advanced Photon Source, Argonne
National Laboratory) using synchrotron radiation tuned to the Ag
KR line, λ ) 0.559 40 Å. The detector was set at a distance of
5.000 cm from the crystal. For data collection φ scan frames were
Experimental Section
Materials and Instrumentation. All solvents and reagents were
used as received. Known 5-phenyldipyrromethane, 5-(4-methylphe-
nyl)dipyrromethane, 5-(4-nitrophenyl)dipyrromethane, and 5-(4-
methoxyphenyl)dipyrromethane were prepared as described be-
fore.30,31 5-(3,5-Dimethoxyphenyl)dipyrromethane was synthesized
following a general literature procedure and purified by column
chromatography.30 The analytical thin-layer chromatography (TLC)
plates were aluminum backed Silicycle ultrapure silica gel 60, 250
(10) Gross, Z.; Galili, N.; Simkhovich, L.; Saltsman, I.; Botoshansky, M.;
Bla¨ser, D.; Boese, R.; Goldberg, I. Org. Lett. 1999, 1, 599-602.
(11) Gross, Z.; Galili, N.; Saltsman, I. Angew. Chem., Int. Ed. 1999, 38,
1427-1429.
(12) Gryko, D. T. Eur. J. Org. Chem. 2002, 1735-1743.
(13) Gross, Z.; Simkhovich, L.; Galili, N. Chem. Commun. 1999, 599-
600.
(14) Gross, Z.; Golubkov, G.; Simkhovich, L. Angew. Chem., Int. Ed. 2000,
39, 4045-4047.
(15) Meier-Callahan, A. E.; Di Bilio, A. J.; Simkhovich, L.; Mahammed,
A.; Goldberg, I.; Gray, H. B.; Gross, Z. Inorg. Chem. 2001, 40, 6788-
6793.
(16) Simkhovich, L.; Gross, Z. Tetrahedron Lett. 2001, 42, 8089-8092.
(17) Bendix, J.; Dmochowski, I. J.; Gray, H. B.; Mahammed, A.; Simkhov-
ich, L.; Gross, Z. Angew. Chem., Int. Ed. 2000, 39, 4048-4051.
(18) Bendix, J.; Gray, H. B.; Golubkov, G.; Gross, Z. Chem. Commun.
2000, 1957-1958.
(19) Paolesse, R.; Mini, S.; Sagone, F.; Boschi, T.; Jaquinod, L.; Nurco,
D. J.; Smith, K. M. Chem. Commun. 1999, 1307-1308.
(20) Ka, J.-W.; Cho, W.-S.; Lee, C.-H. Tetrahedron Lett. 2000, 41, 8121-
8125.
(21) (a) Gryko, D. T. Chem. Commun. 2000, 2243-2244. (b) Gryko, D.
T.; Koszarna, B. Org. Biomol. Chem. 2003, 1, 350-357.
(22) Gryko, D. T.; Jadach, K. J. Org. Chem. 2001, 66, 4267-4275.
(23) Brin˜as, R. P.; Bru¨ckner, C. Synlett 2001, 442-444.
(24) Asokan, C. V.; Smeets, S.; Dehaen, W. Tetrahedron Lett. 2001, 42,
4483-4485.
(30) Boyle, R. W.; Bru¨ckner, C.; Posakony, J.; James, B. R.; Dolphin, D.
Org. Synth. 1999, 76, 287-293. (The synthesis of 5-phenyldipyr-
romethane on 8+g batches is detailed. We experienced no problems
when scaling the reaction 3-fold.)
(25) Gryko, D. T.; Piechota, K. E. J. Porphyrins Phthalocyanines 2002, 6,
81-97.
(26) Guilard, R.; Gryko, D. T.; Canard, G.; Barbe, J.-M.; Koszarna, B.;
Brande`s, S.; Tasior, M. Org. Lett. 2002, 4, 4491-4494.
(27) Barta, C. A.; Brin˜as, R. P.; Bru¨ckner, C. In Abstracts of Papers, 223rd
ACS National Meeting, Orlando, FL, April 7-11, 2002; American
Chemical Society: Washington, D.C., 2002; CHED-586.
(28) Kadish, K. M.; Lin, X. Q.; Ding, J. Q.; Wu, Y. T.; Araullo, C. Inorg.
Chem. 1986, 25, 3236-3242.
(31) Littler, B. J.; Miller, M. A.; Hung, C.-H.; Wagner, R. W.; O’Shea, D.
F.; Boyle, P. D.; Lindsey, J. S. J. Org. Chem. 1999, 64, 1391-1396.
(32) SMART V5.622 (2001) and SAINT V6.02A (2001) programs, Bruker
AXS, Inc., Madison, WI. SADABS v2.03 (2000) was used for the
application of semi-empirical absorption and beam corrections,
SHELXTL v6.1 (2000) was used for the structure solution and
generation of figures and tables, both by G. M. Sheldrick, University
of Go¨ttingen, Germany and Bruker AXS, Inc. Neutral-atom scattering
factors were used as stored in the SHELXTL v6.1.
(29) Scheidt, W. R.; Mondal, J. U.; Eigenbrot, C. W.; Adler, A.;
Radonovich, L. J.; Hoard, J. L. Inorg. Chem. 1986, 25, 795-799.
1674 Inorganic Chemistry, Vol. 42, No. 5, 2003

Efficient Synthesis of TPCH3 and TTCH3
Table 2. Crystal Data and Structure Refinement for TTCAgIII‚C7H8
empirical formula
fw, g/mol
temp, °C
space group
unit cell dimens
a, Å
C40H29N4Ag‚C7H8
765.68
-100
C2/c (No. 15)
vol, Å3
Z
λ, Å
7121.5(10)
8
0.559 40
1.428
D
calcd, Mg/m3
µ, cm-1
3.29
21.4679(19)
20.7606(19)
16.0122(11)
90
93.700(4)
90
final R indices [I > 2σ(I)]a
R indices (all data)a
R1 ) 0.0453, wR2 ) 0.1131
R1 ) 0.0508, wR2 ) 0.1171
b, Å
c, Å
R, deg
â, deg
γ, deg
a R1 ) ∑||Fo| - |Fc||/∑|Fo|; wR2 ) [∑w(Fo
Fc )2/∑w(Fo )2]1/2; w-1 ) [σ2(Fo ) + (aP)2 + bP] where P ) (Fo + 2Fc )/3 where a and b are refined
2 -
2
2
2
2
2
quantities.
measured for a duration of 1 s at 0.3° intervals (Θ range, 2.37-
22.02°). Limiting indices were as follows: -28 < h < +28, -27
< k < +27, -21 < l < +21. The data frames were processed
using the program SAINT. The data were corrected for decay,
Lorentz, and polarization effects as well as absorption (maximum
and minimum transmissions, 0.9967 and 0.9951) based on the
multiscan technique using SADABS.
The structure was solved by a combination of direct methods
(SHELXTL v6.1) and the difference Fourier technique and refined
by full-matrix least squares on F2 (40 697 reflections collected, 8422
unique, Rint ) 0.0840). Non-hydrogen atoms were refined with
anisotropic displacement parameters. Hydrogen atoms were either
located directly or calculated on the basis of geometric criteria and
treated with a riding model. A disordered toluene molecule is
present. Since a suitable disorder model was not forthcoming, the
molecule was simply refined at full occupancy. The refinement
converged satisfactorily. Crystal structure and refinement data for
TTCAgIII‚C7H8 are summarized in Table 2.
CH2Cl2 solvent and a reaction time of 1 h at 0 °C. We empirically
found that these conditions (solvent and temperature) gave higher
yields than the conditions described for TPCH3. Spectroscopic and
analytical data are as previously reported.33 Rf ) 0.77 (silica gel-
CHCl3).
5,10,15-Tris(4-methoxyphenyl)corrole
(T(4-MeO)PCH3).
T(4-MeO)PCH3 was prepared in 20% yield (2 mmol scale) from
5-(4-methoxyphenyl)dipyrromethane, 4-methoxybenzaldehyde, and
pyrrole according to the general procedure. Spectroscopic and ana-
lytical data are as previously reported.9 Rf ) 0.59 silica gel-CHCl3.
5,10,15-Tris(3,5-dimethoxyphenyl)corrole
(T(3,5-MeO)-
PCH3). T(3,5-MeO)PCH3 was prepared in 15% yield (1.5 mmol
scale) from 5-(3,5-dimethoxyphenyl)dipyrromethane, 3,5-dimeth-
oxybenzaldehyde, and pyrrole according to the general procedure.
Rf ) 0.53 (silica gel-CHCl3). UV-vis (CH2Cl2): λmax, nm (log ꢀ)
417 (4.75), 527 (sh, 3.68), 575 (3.96), 616 (3.88), 648 (3.84), 721
(sh, 3.42). 1H NMR (400 MHz, CDCl3): δ 8.7 (br s, 4H), 7.4-7.6
(m, 6H), 6.9 (s, 3H), 4.0 (s, 18), -2.1 (br s, 2H). HR-MS (FAB-
PEG, MH+): Calcd for C43H38N4O6, 707.2870; found: 707.2903.
meso-Triphenylcorrole (TPCH3). General Procedure. Ben-
zaldehyde (2 with Ar ) phenyl, 76 mL, 0.75 mmol) was added to
a stirred solution of 5-phenyldipyrromethane (1 with Ar ) phenyl,
1.0 g, 4.5 mmol)30 in CH3CN (30 mL) under an atmosphere of N2.
TFA (58 mL, 0.75 mmol) was added, and, after 3 h of stirring at
ambient temperature, the reaction was quenched by addition of Et3N
(0.10 mL, 0.75 mmol). DDQ (0.85 g, 3.75 mmol; alternatively
chloranil can be used) dissolved in toluene (30 mL) was added.
The quickly darkening mixture was stirred overnight. The volume
of the mixture was reduced to little less than half by rotary
evaporation, and the resulting mixture was separated by column
chromatography (silica, 50% petroleum ether 30-60/CH2Cl2). The
first major dark green fraction was collected and evaporated to
dryness. Recrystallization of the residue from ethanol/water afforded
140 mg (35% yield) of TPCH3 as a dark green powdery solid of
analytical purity. The procedure was applicable to the reaction of
9 mmol of 2 to yield 1.9 g of TPCH3 (column size 8 × 45
cm). Spectroscopic and analytical data as reported.33 1H NMR (400
MHz, CDCl3): δ 8.83 (br s, 4H), 8.50 (br s, 4H), 8.33 (d, J ) 5
Hz, 4H), 8.15 (d, J ) 5 Hz, 2H), 7.85-7.70 (m, 9H) (data included
for comparison). 1H NMR (400 MHz, CDCl3 - 1.01 equiv of
TFA-d1): δ 8.82 (d, J ) 4.04, 2H), 8.77 (d, J ) 4.64 Hz, 2H),
8.49-8.41 (m, 4H), 8.27 (d, J ) 7.34, 4H), 8.08 (d, J ) 6.16, 2H),
7.75-7.60 (m, 9H). 13C NMR (100 MHz, CDCl3 - 1.01 equiv of
TFA-d1): δ 142.2, 139.8, 135.0, 134.7, 131.2, 127.9, 127.3-127.1
(overlapping signals), 125.7, 115.7, 109.7.
5,10,15-Tris(4-nitrophenyl)corrole (T(4-NO2)PCH3). T(4-NO2)-
PCH3 was prepared in 17% yield (1.5 mmol scale) from 5-(4-nitro-
phenyl)dipyrromethane, 4-nitrobenzaldehyde, and pyrrole according
to the procedure described for TPCH3. Rf ) 0.59 (silica gel-CHCl3).
Spectroscopic and analytical data are as previously reported.33
General Silver Insertion Procedure. meso-Triarylcorrole (0.1
mmol) was dissolved in pyridine (10 mL), and silver(I) acetate (55
mg, 0.33 mmol) was added. The deep green corrole solution turns,
in due course with the metal insertion, a deep dark red. Quantitative
silver insertion takes place upon warming of the solution to ∼80
°C (TLC or UV-vis control). Upon completion, the reaction
mixture is filtered through a plug of Celite, the solvent is removed
on a rotary evaporator, and the residue is subjected to column or
preparative thin-layer plate chromatography (silica, 50% petroleum
ether 30-60/CH2Cl2).
[meso-Triphenylcorrolato]silver(III) (TPCAgIII). TPCAgIII was
prepared in 78% yield (1 mmol scale) according to the general
procedure. Dark purple microcrystalline crystals were developed
by slow evaporation of a toluene solution and dried under high
vacuum at 25 °C. Rf ) 0.86 (silica- toluene/40% petroleum
1
ether). H NMR (400 MHz, CDCl3): δ 7.26-7.31 (m, 9H), 8.19
(d, J ) 8 Hz, 2H), 8.29 (d, J ) 8 Hz, 4H), 8.67 (d, J ) 4 Hz,
2H), 8.71 (d, J ) 4 Hz, 2H), 8.95 (d, J ) 4 Hz, 2H), 9.03 (d,
J ) 4 Hz, 2H). 13C NMR (100 MHz, acetone-d6): δ 141.2, 140.3,
137.7, 135.4, 134.6, 134.5, 134.0, 129.4, 127.7, 127.6, 127.5, 127.4,
5,10,15-Tri-p-tolylcorrole (TTCH3). TTCH3 was prepared in
17% yield (10 mmol scale) from 5-(p-tolyl)dipyrromethane and
p-tolylaldehyde following the general procedure but using dry
127.2, 126.7, 125.4, 119.6, 118.3, 117.7. UV-vis (CH2Cl2): λmax
,
nm (log ꢀ) 423 (5.11), 499 (sh, 3.66), 523 (sh, 3.87), 544 (sh, 4.03),
561(4.31), 582 (4.52). MS (APCI+, 100% CH3CN): m/e 630
(100, M+), isotope pattern of molecular ion cluster matches
composition C37H23N4Ag. HR-MS (FAB-PEG, M+): Calcd for
(33) Paolesse, R.; Nardis, S.; Sagone, F.; Khoury, R. G. J. Org. Chem.
2001, 66, 550-556.
Inorganic Chemistry, Vol. 42, No. 5, 2003 1675

Bru1ckner et al.
a
C37H23N4107Ag, 630.0974; found: 630.1001. Anal. Calcd for
C37H23N4Ag (found): C, 70.38 (70.10); H, 3.67 (3.59); N, 8.87
(5.57).
Scheme 1
[meso-Tri-p-tolylcorrolato]silver(III) (TTCAgIII). TTCAgIII was
prepared in 75% yield (0.5 mmol scale) according to the general
procedure. Dark purple needles were extracted by slow evaporation
of a toluene solution. Rf ) 0.84 (silica- toluene/40% petroleum
1
ether 30-60). H NMR (400 MHz, CDCl3): δ 9.16 (d, J ) 4,
2H), 8.95 (d, J ) 4, 2H), 8.74 (d, J ) 4, 2H), 8.71 (d, J ) 4, 2H),
8.20 (d, J ) 4 Hz, 4H), 8.10 (d, J ) 4 Hz, 2H), 7.55-7.64 (m,
6H), 2.68 (overlapping s, 9H). 13C NMR (100 MHz, acetone-d6):
δ 138.64, 138.31, 137.75, 137.64, 137.4, 135.9, 134.8, 134.6, 130.8,
129.6, 128.7, 128.4, 125.6, 119.8, 118.9, 117.9, 113.7, 21.7, 21.5.
UV-vis (CH2Cl2): λmax, nm (log ꢀ) 423 (4.98), 497 (sh), 524 (sh),
545 (sh), 560 (4.15), 586 (4.43) nm. MS (APCI+, 100% CH3CN):
m/e 672 (100, M+), isotope pattern of molecular ion cluster matches
composition C40H29N4Ag. HR-MS (FAB-PEG, M+): Calcd for
C40H29N4107Ag, 672.1443; found: 672.1437. Anal. Calcd for
C40H29N4Ag‚C7H8 (found): C, 73.44 (73.31); H, 5.24 (5.21); N,
7.29 (7.15).
a Reaction conditions: (i) TFA, CH3CN at 25 °C or CH2Cl2 at 0 °C. (ii)
(a) DDQ or chloranil; (b) column chromatography. (iii) (a) 3.3 equiv of
AgAc, pyridine, ∆; (b) column chromatography.
[meso-Tris(4-methoxyphenyl)corrolato]silver(III) (T(4-MeO)-
PCAgIII). T(4-MeO)PCAgIII was prepared in 80% yield (0.1 mmol
scale) according to the general procedure. Rf ) 0.81 (silica- 20%
closed to provide, after aromatization of the macrocycle, the
corresponding corroles.20,23-25,33 Such oxidatively induced
formations of direct pyrrole-pyrrole linkages have prece-
dents in pyrrole and pyrrolic macrocycle chemistry and
constitute the ring-closing step in all recent triarylcorrole
syntheses.34-37 Hence, key to an efficient triarylcorrole
synthesis is the formation of a high yield of the corresponding
tetrapyrrane (Scheme 1).
meso-Aryl substituted oligopyrranes (3) are compounds
of limited stability.20,36,38 Although they can be isolated and
characterized and their oxidation proves unambiguously their
role as intermediates in the triarylcorrole formation,20,36 their
isolation is not required for the purpose of an efficient corrole
synthesis. Instead, their in situ preparation and immediate
oxidation is sufficient.20,23,24,33 It is, however, important that
the intermediate tetrapyrranes be formed without concomitant
formation of a porphyrinogen as the subsequent oxidation
step would convert this cyclic tetrapyrrolic intermediate to
porphyrins.39 Separation of meso-tetraarylporphyrins from
their analogous meso-triarylcorroles is challenging and
impractical when preparing corroles in millimole scales. In
fact, the simultaneous formation of porphyrins and corroles
during the one-step syntheses of corroles from aldehydes and
pyrrole constitutes the major drawback of this otherwise
appealing method.9,19
1
petroleum ether 30-60/CH2Cl2). H NMR (400 MHz, CDCl3): δ
8.97 (d, J ) 4.3 Hz, 2H), 8.88 (d, J ) 4.6 Hz, 2H), 8.64 (d, J )
4.8 Hz, 2H), 8.61 (d, J ) 4.3 Hz, 2H), 8.20 (d, J ) 8.4 Hz, 4H),
8.07 (d, J ) 8.5 Hz, 2H), 7.36 (d, J ) 8.5 Hz, 4H), 7.31 (d, J )
8.5 Hz, 2H), 4.11 (s, 6H), 4.10 (s, 3H). 13C NMR (100 MHz,
CDCl3): δ 159.8, 159.5, 138.8, 135.9, 135.7, 135.0, 134.0, 133.1,
131.1, 129.5, 125.5, 119.6, 118.9, 117.7, 113.5, 113.2, 55.8. UV-
vis (CH2Cl2): λmax, nm (log ꢀ) 423 (5.14), 491 (sh, 3.71), 523 (3.97),
547 (sh, 4.14), 559 (4.29), 589 (4.61) nm. HR-MS (FAB-PEG,
M+): Calcd for C40H29N4O3107Ag, 720.1291; found: 720.1257.
[meso-Tris(3,5-dimethoxyphenyl)corrolato]silver(III) (T(3,5-
MeO)PCAgIII). T(3,5-MeO)PCAgIII was prepared in 60% yield (0.1
mmol scale) according to the general procedure. Dark purple
crystals by solvent exchange from CH2Cl2 to ethanol. Rf ) 0.84
(silica, 20% petroleum ether 30-60/CH2Cl2). 1H NMR (400 MHz,
CDCl3): δ 9.21 (d, J ) 4.4 Hz, 2H), 9.08 (d, J ) 4.8 Hz, 2H),
8.86 (d, J ) 4.4 Hz, 2H), 8.84 (d, J ) 4.8, 2H), 7.50 (d, J ) 2.3
Hz, 4H), 7.41 (d, J ) 2.3 Hz, 2H), 6.89 (m, 3H), 4.02 (s, 12H),
3.99 (s, 6H). 13C NMR (100 MHz, CDCl3): δ 160.1, 159.8, 143.4,
142.4, 137.8, 135.9, 135.8, 129.7, 125.7, 120.0, 118.3, 118.1, 113.5,
113.2, 100.4, 100.2, 55.9. UV-vis (CH2Cl2): λmax, nm (log ꢀ) 424
(5.05), 497 (sh), 523 (sh), 562 (4.32), 581 (4.50). HR-MS (FAB-
PEG, M+): Calcd for C43H35N4O6107Ag, 810.1608; found: 810.1581.
[meso-Tris(4-nitrophenyl)corrolato]silver(III) (T(4-NO2)-
PCAgIII). T(4-NO2)PCAgIII was prepared in 60% yield (0.1 mmol
scale) according to the general procedure. Dark purple crystals by
solvent exchange from CH2Cl2 to EtOH. Rf ) 0.78 (silica, 20%
petroleum ether 30-60/CH2Cl2). 1H NMR (400 MHz, DMSO-d6):
δ 9.40 (d, J ) 4.5, Hz, 2H), 9.08 (d, J ) 4.8 Hz, 2H) 8.87 (d, J )
4.5, 2H), 8.84 (d, J ) 4.8 Hz, 2H), 8.75 (d, J ) 8.6 Hz, 4H), 8.72
(d, J ) 8.6 Hz, 4H), 8.59 (d, J ) 8.6 Hz, 2H), 8.49 (d, J ) 8.6 Hz,
2H). UV-vis (CH2Cl2): λmax, nm (log ꢀ) 441 (4.94), 547 (sh, 4.12),
589 (4.56). MS (APCI+, 100% CH3CN): m/e 766 (100, MH+),
isotope pattern of molecular ion cluster matches composition
C37H21N7O6Ag.
Our approach toward the formation of tetrapyrranes, while
suppressing the formation of porphyrinogens, is to react a
benzaldehyde (2) with a large molar excess of dipyrro-
methane (1, 6:1 molar ratio of dippyrane to benzaldehyde)
under Lindsey’s nonscrambling conditions.40 The tetrapyrrane
(34) Sessler, J. L.; Seidel, D.; Lynch, V. J. Am. Chem. Soc. 1999, 121,
11257-11258.
(35) Narayanan, S. J.; Sridevi, B.; Chandrashekar, T. K.; Englich, U.;
Ruhlandt-Senge, K. Org. Lett. 1999, 1, 587-590.
(36) Cho, W.-S.; Lee, C.-H. Tetrahedron Lett. 2000, 41, 697-701.
(37) Seidel, D.; Lynch, V.; Sessler, J. L. Angew. Chem., Int. Ed. 2002, 41,
1422-1425.
Results and Discussion
(38) Bru¨ckner, C.; Sternberg, E. D.; Boyle, R. W.; Dolphin, D. Chem.
Commun. 1997, 1689-1690.
(39) Dolphin, D. J. Heterocyclic Chem. 1970, 7, 275-283.
Syntheses of meso-Triarylcorroles (TPCH3 and TTCH3).
meso-Triaryltetrapyrranes (such as 3) can be oxidatively ring-
1676 Inorganic Chemistry, Vol. 42, No. 5, 2003

Efficient Synthesis of TPCH3 and TTCH3
As will be demonstrated below, the NMR and UV-vis
spectral characteristics of the protonated corrole serve as
reference points for the interpretation of the metalation
experiments.
Syntheses [meso-Triarylcorrolato]silver(III). Upon warm-
ing a solution of meso-triarylcorrole (TPCH3 and TTCH3,
respectively) with a ∼3.3 M excess of silver(I) acetate in
pyridine, the initially green solution turns deep red within a
few minutes. A fine precipitate of Ag(0) and/or the formation
of a silver mirror on the wall of the reaction flask is observed.
As gauged by TLC, only one major nonpolar product is
formed (Rf ) 0.86 (toluene/40% petroleum ether)). Evapora-
tion of the solvent followed by column chromatographic
separation of the main product produces a deep purple
microcrystalline powder in excellent yields (∼80%). The
products are air-, light- and water-stable and dissolve in a
wide variety of solvents.
Figure 2. Aromatic region of the 1H NMR (CDCl3, 400 MHz) of (A)
TPCH3, (B) TPCH3 in the presence of 1 equiv of TFA-d1, and (C) TPCAgIII.
formed is oxidized in situ with DDQ or chloranil. This
reaction sequence leads to the formation of none or only
traces of the corresponding tetraarylporphyrin (<1%). An
increase of the molar excess of the dipyrromethane does not
lead to an increase of the corrole yield. The main side
products formed are pyrrolic polymers and dipyrrins,41 polar
materials not impeding the chromatographic isolation of the
nonpolar triarylcorroles. Using this method, triarylcorroles
uncontaminated with porphyrins could be prepared in up to
35% yield (based on limiting reagent 2, formation of up to
1.9 g of TPCH3 or TTCH3 per run). The apparent waste of
the dipyrromethane 1 is balanced by the applicability of the
synthesis to relatively large scales and the purity of the
resulting corrole and is mitigated by the ease at which
dipyrromethanes have become accessible.30 This methodol-
ogy adds to a number of largely complementary techniques
which were devised in the past 3 years for the synthesis of
meso-triarylcorroles9,10,21,22,25,26,36 and meso-triarylheterocor-
roles.35,36,42
The Ag(III) complex forms in a disproportionation reac-
tion: 3AgI f AgIII + 2Ag0. Reduction of the 3.3 M excess
of silver(I) acetate reduces the yield of the reaction, and the
metal insertion reaction is independent of the presence or
absence of oxygen.
Spectroscopic Characterization of TPCAgIII and
TTCAgIII. The IR of the complexes provided no indication
for the presence of an NH bond. HR-FAB mass spectrometry
determined the m/z composition of the singly charged species
to correspond to C37H23N4Ag and C40H29N4Ag, respectively,
the expected composition for the AgIII corrolato complexes.
The compounds are, as judged by their nonbroadened NMR
spectra, diamagnetic (Figure 2C). The NMR spectra of the
silver complexes largely resemble those of the protonated
free base corrole (Figure 2B), suggesting that the central
metal is coordinated in an N4 fashion, while the general low-
field shift of the â-proton signals in the metal complex
indicates a larger degree of planarity as compared to the
Free base corroles were described amply before, but a
1
protonated species. An expansion of the â-region of the H
1
number of new observations are noteworthy. The H and
NMR spectrum of select AgIII corrolato complexes allowed
13C NMR spectra of free base corroles is severely broadened
(Figure 2A). The X-ray structure of a free base meso-
triphenylcorrole has proven that it is nonplanar.10 One of
the pyrrolic subunits is tilted so as to reduce the steric
crowding of the three NH protons in the central cavity. Thus,
the broadened NMR is likely the result of dynamic processes
involving the scrambling of the position of the tilted pyrrolic
unit and/or swinging of the tilted pyrrolic unit through the
center of the macrocycle. Accordingly, rigidified triarylcor-
roles containing sterically demanding o-phenyl substituents
display sharper NMR signals.25 Addition of 1 equiv of TFA
protonates the corrole.11 This evidently also rigidifies the
macrocycle, allowing the recording of sharp NMR signals
(Figure 2B). Importantly, the NMR allows the conclusion
that protonation does not invert one of the pyrrolic units as
observed in meso-triarylsapphyrin, an expanded corrole.43
4
the identification of the J coupling constant of 0.8 Hz for
the coupling of the â-protons with the 107/109Ag nuclei (I )
1/2). We thus formulate the compounds to be square planar
d8 Ag(III) complexes. Though Ag(III) complexes were
considered a rarity,44,45 our findings find a parallel in the
Ag(III) complexes of porphyrins accessible by oxidation of
Ag(II) porphyrins using chemical or electrochemical oxida-
tion methods.46-48 Further, the silver complexes of singly
and doubly N-confused porphyrins as well as the closely
related carbaporphyrins (featuring N3C and N2C2 donor sets)
were also assigned +III oxidation states.49-51
(43) Chmielewsky, P. J.; Latos-Grazynski, L.; Rachlewicz, K. Chem.-Eur.
J. 1995, 1, 68-73.
(44) Cotton, F. A.; Wilkinson, G.; Murillo, C. A.; Bochmann, M. AdVanced
Inorganic Chemistry; 6th ed.; John Wiley & Sons: New York, 1999.
(45) Abedini, M.; Farnia, M.; Kahani, A. J. Coord. Chem. 2000, 50, 39-
42.
(40) Rao, P. D.; Littler, B. J.; Geier, G. R., III; Lindsey, J. S. J. Org. Chem.
2000, 65, 1084-1092.
(46) Antipas, A.; Dolphin, D.; Gouterman, M.; Johnson, E. C. J. Am. Chem.
Soc. 1978, 100, 7705-7709.
(41) Bru¨ckner, C.; Karunaratne, V.; Rettig, S. J.; Dolphin, D. Can. J. Chem.
1996, 74, 2182-2193.
(47) Kadish, K. M.; Lin, X. Q.; Ding, J. Q.; Wu, Y. T.; Araullo, C. Inorg.
Chem. 1986, 25, 3236-3242.
(42) Sridevi, B.; Narayanan, S. J.; Chandrashekar, T. K.; Englich, U.;
Ruhlandt-Senge, K. Chem.-Eur. J. 2000, 6, 2554-2563.
(48) Milgrom, L. R.; Jones, C. C. J. Chem. Soc., Chem. Commun. 1988,
576-578.
Inorganic Chemistry, Vol. 42, No. 5, 2003 1677

Bru1ckner et al.
Figure 3. UV-vis spectra (CDCl3) of (-) TTCAg and (--) T(4-NO2)-
TCAgIII.
Figure 4. XPS signals in the Ag 3d3/2 and 3d5/2 peak region for TTCAgIII
evaporated onto a silicon wafer. For a tabulation of the data see Table 1.
UV-Vis Spectral Characterization. The UV-vis spectra
of the silver complexes TTCAg and T(4-NO2)TCAg are
shown in Figure 3. The general features of the spectra follow
expectations for metallocorroles. The λmax ) 586 nm for the
spectrum of TTCAg is significantly blue-shifted compared
to the closed d-shell complex [meso-tetra(pentafluorophenyl)-
corrolato]aluminum(III) (λmax ) 620 nm).52 Silver(III) cor-
rolato complexes therefore display, using the spectral clas-
sification of metalloporphyrins, a typical hypso spectrum.53
Comparing the spectra for TTCAg and the p-nitro substituted
derivative T(4-NO2)TCAg, a remarkable influence of the
p-phenyl substituents on the spectra of the silver(III) corrolato
complexes is observed. Ghosh and co-workers recently
observed a similar effect in the electronic spectra of meso-
triarylcorrolato FeIVCl, FeIVOFeIV, MnIVCl, and Cu(III)
complexes.9,54 It was interpreted as an indication for a
significant ligand-to-metal charge-transfer character of certain
transitions in the Soret region of the spectrum and was found
to be specific to high-oxidation-state corrolato complexes.9,46
The silver(III) corrolato complexes follow this observation
but to a different extent. While the Soret band in the corrolato
Cu(III) complexes shifted bathochromically going from p-H
(410 nm), to p-CH3 (+8 nm), to p-OCH3 (+23 nm) and
shifted hypsochromically upon substitution with electron-
withdrawing substituents (p-CF3, -3 nm; C6F5-, -4 nm),
we observe the Soret for the Ag(III) complexes with p-H,
p-CH3, p-OCH3 (423 nm), and 3,5-di-OCH3 (+1 nm) to be
almost invariable, whereas the p-NO2 substituted derivative
exhibits a bathochromic shift of 17 nm in conjunction with
a significantly broadened spectrum.
porphyrinato complexes, this property was correlated with
the existence of low-lying ligand-to-metal charge-transfer
46
2
2
bands (a1u(π), a2u(π) f dx -y ). Supporting this, the near-
IR spectra of the Ag(III) complexes show broad features in
the region from 650 to 850 nm, not unlike those observed
in the [porphyrinato]AgII complexes.46
Demetalation Reaction. The corrolato Ag(III) complexes
slowly demetalate in CHCl3 from which traces of acid were
not removed, presumably via a reductive mechanism. Hence,
treatment of a CHCl3 or CH2Cl2 solution of TPCAgIII or
TTCAgIII with concentrated aqueous HCl in a biphasic
system leads within minutes to complete demetalation (TLC
control) of the silver complex and precipitation of silver(I)
chloride. Parallels to the electrochemical reductive or acid-
induced demetalations of TPPAgII are clearly evident.55,56
As far as we are aware, this constitutes the first reversible
metalation/demetalation procedure of metallocorroles. Re-
markably, treatment of the silver corrolato complexes with
gaseous H2S under neutral conditions does not lead to
demetalation. The use of HI leads to the formation of free
base and â-iodinated products. The ease of the iodination
reaction mirrors the facile exhaustive â-bromination of
corroles.9,33
X-ray Photoelectron Spectroscopy Study of TTCH3 and
TTCAgIII. XPS has been shown to be an appropriate tool
for probing the charge distribution indicative of formal
oxidation states in structurally homogeneous systems. Table
1 tabulates the results of an XPS study of the free base
corrole TTCH3 and its silver complex TTCAgIII in compari-
son to literature data reported for meso-tetraphenylporphyrin
TPPH2 and its Ag(II) (TPPAgII) and Ag(III) ([TPPAgIII]-
(ClO4)) complexes.57,58 The C 1s and N 1s binding energies
measured for TTCH3 are equivalent to those found in TPPH2,
reflecting the similarity of their carbon sp2 frameworks
containing pyrrole- (sp3) and imine- (sp2) type nitrogens
(albeit their relative atom-type ratios are different). The Ag
3d3/2 and 3d5/2 binding energies (Figure 4) match very well
Parallel to [porphyrinato]AgII and -AgIII complexes,46
TTCAgIII is nonfluorescent (at 25 °C, CH2Cl2). In the
(49) Furuta, H.; Ogawa, T.; Uwatoko, Y.; Araki, K. Inorg. Chem. 1999,
38, 2676-2682.
(50) Furuta, H.; Maeda, H.; Osuka, A. J. Am. Chem. Soc. 2000, 122, 803-
807.
(51) (a) Muckey, M. A.; Lash, T. D. Abstracts of Papers, 221st ACS
National Meeting of the American Chemical Society, San Diego, CA,
April 1-5, 2001; American Chemical Society: Washington, D.C.,
2001; ORGN-715. (b) Muckey, M. A.; Szczepura, L. F.; Ferrence, G.
M.; Lash, T. D. Inorg. Chem. 2002, 41, 4840-4842.
(52) Mahammed, A.; Gross, Z. J. Inorg. Biochem. 2002, 88, 305-309.
(53) Gouterman, M. In The Porphyrins; Dolphin, D., Ed.; Academic
Press: New York, 1978; Vol. III, pp 1-165.
(55) Giraudeau, A.; Louati, A.; Callot, H. J.; Gross, M. Inorg. Chem. 1981,
20, 769-772.
(56) Krishnamurthy, M. Inorg. Chem. 1978, 17, 2242-2245.
(57) Karweik, D. H.; Winograd, N. Inorg. Chem. 1976, 15, 2336-2342.
(58) Karweik, D.; Winograd, N.; Davis, D. G.; Kadish, K. M. J. Am. Chem.
Soc. 1974, 96, 591-592.
(54) Steene, E.; Wondimagegn, T.; Ghosh, A. J. Phys. Chem. B 2001, 105,
11406-11413 (Correction/addition: J. Phys. Chem. B 2002, 106,
5312.
1678 Inorganic Chemistry, Vol. 42, No. 5, 2003

Efficient Synthesis of TPCH3 and TTCH3
Figure 5. Molecular structure (H-atoms and solvent omitted for clarity;
thermal ellipsoids at 50% probability) of TTCAgIII‚C7H8: (A) top view,
with atom labeling; (B) side view along axis of twist (H-atoms and all atoms
of the meso-p-tolyl groups save for the ipso-carbons removed for clarity).
Select bond distances (Å): Ag-N1, 1.966(2); Ag-N2, 1.955(2); Ag-N3,
1.952(2); Ag-N4, 1.944(2). Angles (deg): N2-Ag-N1, 96.87(9);
N4-Ag-N1, 91.82(9); N3-Ag-N2, 91.35(9); N4-Ag-N3, 80.76(9);
N3-Ag-N1, 169.76(9); N4-Ag-N2, 169.14(9). Deviation from planarity,
root mean square of C23N4 plane: 0.186 Å.
Figure 6. Crystal packing of TTCAgIII‚C7H8, shown along the crystal-
lographic a axis.
with those previously measured for the Ag(III) salt [TPPAgIII]-
(ClO4) and are significantly shifted toward higher binding
energies as compared to the energies measured for the Ag-
(II) complex TPPAgII, further supporting the presence of a
genuine Ag(III) complex. As expected, 3-fold deprotonation
and metalation renders all four nitrogens XPS equivalent,
supporting the square planar in-plane coordination expected
for a d8 metal ion.
Single-Crystal X-ray Structure Analysis of TTCAgIII‚
C7H8. Proof for the constitution of the Ag(III) complex
TTCAgIII, as its toluene solvate, was provided by single
crystal X-ray crystallography. As only exceedingly fine
needles (0.01 × 0.01 × 0.02 mm) could be grown by slow
evaporation of a toluene solution of TTCAgIII, their crystal-
lographic study was performed at a synchroton beam line at
the Advanced Photon Source, Argonne National Laboratory.
Crystal data are tabulated in Table 2. A top and side view
of the structure is shown in Figure 5; the crystal packing
diagram is provided in Figure 6.
The general molecular structure of TTCAgIII‚C7H8 is as
expected for a meso-triaryl substituted corrolato complex of
a d8 metal (Figure 5A). The absence of any counterion in
conjunction with the absence of any discernible NH protons
further confirm the +III oxidation state of the central metal.
The central metal is coordinated in a square-planar fashion
by the four central nitrogens of the ligand, but the deviations
from an ideal square-planar coordination sphere are consider-
able. The small N3-Ag-N4 bond angle (80.76(9)°) origi-
nates in the smaller bite angle of the two nitrogens enforced
by the direct pyrrole-pyrrole linkage and is a general
characteristic of metallocorroles.4,15,18,59
The Ag-N bond distances measured vary from 1.966(2)
Å (for Ag-N1) to 1.944(2) Å (for Ag-N4). In comparison,
the Ag-N bond distances in the planar Ag(II) complex
TPPAgII are 2.082(3) and 2.101(3) Å.29 Interestingly, the
Ag-N bond distances measured for the near-planar Ag(III)
complexes of carbaporphyrins are similarly long as in the
Ag(II) porphyrin complex, namely, 2.03(2)-2.08(2),49
2.047(7)-2.064(5),50 and 2.038(4) - 2.084(4) Å,51 respec-
tively. Thus, the Ag-N bond distances in these porphyrinic
macrocycles are less a reflection of the oxidation state of
the central metal but a reflection of the cavity size of the
relatively rigid macrocycles. This further allows the conclu-
sion that the origin of the capability of carbaporphyrins and
corroles to stabilize high oxidation states of the central metal
has a strong electrostatic component. Both ligands are
trianionic as compared to the dianionic porphyrins. The better
s-donor capabilities of the carbaporphyrins are evidently
making up for the smaller size of the corroles. Porphyrins
as well as corroles are equally “noninnocent” ligands capable
of donating π-density into the metal centers.5,6
The corrole chromophore in TTCAgIII‚C7H8 exhibits a
slightly saddled conformation (i.e. the pyrrole rings are
alternately tilted above/below the mean plane of the corrole).
A twist axis bisects the C14-C15 bond and passes through
the central metal and the C5 meso-position. Analogous to
the effects of any saddling or ruffling in porphyrins, the metal
(59) Simkhovich, L.; Galili, N.; Saltsman, I.; Goldberg, I.; Gross, Z. Inorg.
Chem. 2000, 39, 2704-2705.
Inorganic Chemistry, Vol. 42, No. 5, 2003 1679

Bru1ckner et al.
is essentially not displaced from the mean plane of the
nitrogen donors (only 0.003 Å out of the N1-N4 plane).
Hence, the short Ag-N bond distances observed in TTCAgIII‚
C7H8 are the result of the smaller corrole cavity size,
amplified by the distortion of the macrocycle from planarity
(Figure 5B), though it is not clear whether this distortion is
caused by crystal packing effects or whether it is, in analogy
to the conformation of many porphyrin complexes of the
(small) Ni(II) ion,60-62 metal-induced.
This is the first time that a saddled conformation was
observed for a metallocorrole, although Ghosh and co-
workers most recently calculated the conformation of [meso-
tri(pentafluorophenyl)corrolato]copper(III) to be saddled.9
The calculated bond distances for the C-C and C-N bonds
in the Cu(III) complex vary, however, from those observed
in the saddled Ag(III) complex.
Figure 6 shows the packing diagram for TTCAgIII‚C7H8.
The corrolato complexes pack in square grid sheets. The
sheets are stacked resulting in Ag-Ag separations of 4.31
and 4.04 Å. The square channels between the corrolato stacks
are filled with solvate, also forming stacked columns. The
observed arrangement is not unlike that found in the crystal
structure of a number of meso-tetraphenylporphyrin deriva-
tives.63
chemistry that the ligand environment largely determines the
stable oxidation state of a coordinated metal. The nonplanar
conformation of TTCAgIII indicates that the coordination
chemistry and physical properties of corroles could be
modulated by similar conformational effects as porphyrins.64
Further interesting coordination chemistry of metallocorroles
containing metals in unusually high oxidation states can be
expected soon, particularly given the ease at which free base
meso-triarylcorroles have become synthetically accessible or
considering their commercial availability.65
Acknowledgment. The work was supported with funds
provided by the University of Connecticut (UConn) Research
Foundation and the donors of the Petroleum Research Fund
(PRF), administered by the American Chemical Society.
C.A.B. thanks the National Science Foundation for an NSF-
REU summer research stipend. We are indebted to Bill Willis
and Steven L. Suib, Department of Chemistry, UConn, for
the measurement of the XPS data. We thank Stephen Capetta,
Department of Chemistry, UConn, for experimental support.
X-ray diffractometry investigations were carried out at
ChemMatCARS during commissioning time of the beamline,
courtesy of J. Viccaro and the University of Chicago.
J.A.K.B. would like to thank D. Cookson and T. Graber for
support at the beamline. ChemMatCARS Sector 15 is
principally supported by the National Science Foundation/
Department of Energy under Grant No. CHE0087817 and
by the Illinois Board of Higher Education. The Advanced
Photon Source is supported by the U.S. Department of
Energy, Basic Energy Sciences, Office of Science, under
Contract No. W-31-109-Eng-38.
Conclusions
In conclusion, meso-triarylcorroles form stable Ag(III)
complexes. These complexes underline once again the special
ability of corroles to induce the stabilization of higher
oxidation states as compared to the corresponding porphyrins.
As more Ag(III) complexes of tetrapyrrolic and related
ligands become known, this oxidation state for silver cannot
be regarded as an exception anymore. In fact, the Ag(III)
complexes underline the classic principle of coordination
Supporting Information Available: Details of the XPS analysis
of TTCH3 and TTCAgIII (PDF) and X-ray crystallographic CIF file
for TTCAgIII‚C7H8. This material is free of charge via the Internet
at http://pubs.acs.org. CIF files are available free of charge via the
Internet at http://www.ccdc.cam.ac.uk. Refer to CCDC reference
number CCDC-202424.
(60) Bru¨ckner, C.; Sternberg, E. D.; MacAlpine, J. K.; Rettig, S. J.; Dolphin,
D. J. Am. Chem. Soc. 1999, 121, 2609-2610.
(61) Jentzen, W.; Simpson, M. C.; Hobbs, J. D.; Song, X.; Ema, T.; Nelson,
N. Y.; Medforth, C. J.; Smith, K. M.; Veyrat, M.; Mazzanti, M.;
Ramasseul, R.; Marchon, J. C.; Takeuchi, T.; Goddard, W. A.;
Shelnutt, J. A. J. Am. Chem. Soc. 1995, 117, 11085-11097.
(62) Kozlowski, P. M.; Rush, T. S., III; Jarzecki, A. A.; Zgierski, M. Z.;
Chase, B.; Piffat, C.; Ye, B.-H.; Li, X.-Y.; Pulay, P.; Spiro, T. J. Phys.
Chem. A 1999, 103, 1357-1366.
IC0261171
(64) Shelnutt, J. A.; Song, X.-Z.; Ma, J.-G.; Jentzen, W.; Medforth, C. J.
Chem. Soc. ReV. 1998, 27, 31-41.
(65) meso-Triarylcorroles are commercially available: Strem Chemicals,
Inc. (www.strem.com).
(63) Byrn, M. P.; Curtis, C. J.; Hsiou, Y.; Khan, S. I.; Sawin, P. A.; Tendick,
S. K.; Terzis, A.; Strouse, C. E. J. Am. Chem. Soc. 1993, 115, 9480-
9497.
1680 Inorganic Chemistry, Vol. 42, No. 5, 2003