Gold(I) and gold(III) corroles

Article abstract of DOI:10.1002/chem.201102348

Corrole complexes with gold(I) and gold(III) were synthesized and their structural, photophysical, and electrochemical properties investigated. This work includes the X-ray crystallography characterization of gold(I) and gold(III) complexes, both chelated by a corrole with fully brominated β-pyrrole carbon atoms. The mononuclear and chiral gold(I) corrole appears to be the first of its kind within the porphyrinoid family, while the most unique property of the gold(III) corrole is that it displays phosphorescence at ambient temperatures. Copyright

Full text of DOI:10.1002/chem.201102348

DOI: 10.1002/chem.201102348
Gold(I) and GoldACTHNUTRGNEUGN(III) Corroles
Elena Rabinovich,[a] Israel Goldberg,*[b] and Zeev Gross*[a]
12294
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Chem. Eur. J. 2011, 17, 12294 – 12301

FULL PAPER
Abstract: Corrole complexes with gold(I) and gold
structural, photophysical, and electrochemical properties investigated. This work
includes the X-ray crystallography characterization of gold(I) and gold(III) com-
plexes, both chelated by a corrole with fully brominated b-pyrrole carbon atoms.
The mononuclear and chiral gold(I) corrole appears to be the first of its kind
ACHTUNGTRNE(NUNG III) were synthesized and their
A
Keywords: chirality · gold · metal-
locorroles · NMR spectroscopy ·
X-ray diffraction
within the porphyrinoid family, while the most unique property of the gold
corrole is that it displays phosphorescence at ambient temperatures.
ACHTUNGTNER(NUNG III)
Introduction
expectations by displaying phosphorescence even at ambient
temperature, but these coordinatively saturated complexes
cannot be utilized as catalysts due to their substitution inert-
ness.[16] We have hence decided to attempt the preparation
The use of gold complexes in catalysis is constantly increas-
ing,[1] mainly by taking advantage of their carbophilic Lewis
acidity for the activation of carbon–carbon p bonds. Reviews
on the broad array of gold-catalyzed reactions reveal that
the majority of homogeneous catalysts used to date are
of goldACHTNUTRGNE(NUG III) corroles, which based on the knowledge about
copper and silver corroles,[17–19] may be expected to form
quite stable d8 square planar and relatively “innocent” com-
plexes (i.e., not containing oxidized ligands). Another focus
was on determining the two other plausible oxidation states
that may be obtained: gold(I) and gold(II).
(PPh3)]+ fragments.[2,3] Di-
goldACHTUNGTRENNUNG(III) halides or cationic [AuCAHTUNGTRENNUGN
valent gold complexes are much more rare and mostly re-
stricted to complexes with unsaturated dithiolate and por-
phyrin ligands,[4,5] where delocalization of the unpaired elec-
tron through the p system is possible.[6] The most prominent
research direction on gold
G
Results and Discussion
their utilization as anticancer drugs, with indications that
they may be of larger potency than cis-platin.[7] Since gold-
Based on the experience regarding the insertion of rhodium
and iridium into tris-pentafluorophenyl corrole, H3-
ACHTUNGTRENNUNG(III) porphyrins may easily be reduced by either metal- or
ligand-centered processes, they are also used as acceptors in
photosynthesis-mimicking dyads[8,9] and triads.[10,11] There is
only a singular report about the catalytic properties of gold-
(tpfc),[16,20,21] it seemed best to use a gold(I) auration agent,
ACHTUNGTRENNUNG
despite the fact that due to the softness of gold(I) it is gener-
ally assumed that it will not effectively coordinate to nitro-
gen atoms.[22] Gold(I) complexes with N-donor ligands are
indeed much less common than those with P-donor ligands,
but the affinity for nitrogen can be increased if one phos-
phine ligand is present because of the efficient p-acceptor
ACHTUNGTRENNUNG
(III) porphyrins (for cycloisomerization of allenones),[12]
which display higher chemoselectivity than other homogene-
ous gold
(III) catalysts.[13] Photophysical properties are also
of interest, albeit the emission of gold(III) porphyrins is nor-
ACHTUNGTRENNUNG
mally only recordable in frozen glass. One exception is the
complex with a modified (N confused) porphyrin: it emits at
nature of the latter.[23] The choice of [MeAu
[ClAu(PPh3)] as the metal source revealed that both did
react with the pyrrole-brominated corrole H3A(Br8tpfc) (1;
Scheme 1). The auration occurred under very mild condi-
tions, that is, in a toluene solution for 20 min at room tem-
perature with almost quantitative yield of the isolated prod-
uct. There was no reaction when THF or chloroform were
used as solvents and, surprisingly and for yet undetermined
ACHTUNGRTENN(UNG PPh3)] and
AHCTUNGTRENNUNG
ambient temperatures, a very rare feature for any gold
CHTUNGTRENNUNG
complex.[14]
We have lately become interested in corrole complexes
with 5d metals for exploring unique photophysical and cata-
lytic properties that they may display, not at least because of
the importance for the pharmaceutical and bioimaging ap-
plications that are currently at the forefront of research on
the “less heavy” metallocorroles.[15] The recently reported
reasons, the non-brominated corrole H3ACTHNUTRGNE(NUG tpfc) could not be
aurated by any of the applied reaction conditions.
bis-amine-coordinated iridium
(III) corroles fulfilled the first
Similar to N-alkylation and rhodium(I) metalation of cor-
roles,[24] the auration of 1 afforded two isomers (2a and 2b,
with the latter as the major product), as deduced by NMR
spectroscopy. Room temperature spectra were very broad
due a variety of dynamic processes, but the resonances re-
corded at low temperature were sharp and informative. Two
sets of NH resonance for each isomer are clearly seen in
Figure 1a: at À0.39 ppm and À3.37 ppm for 2b and at
0.67 ppm and À3.93 ppm for 2a. Resonances attributable to
coordinated PPh3 are located at relatively high field
(6.66 ppm, 6.53 ppm and 5.18 ppm for the major isomer),
due to the diamagnetic ring current effect of the aromatic
macrocycle. The low temperature 19F NMR spectra (Fig-
[a] E. Rabinovich, Prof. Dr. Z. Gross
Department Schulich Faculty of Chemistry
Technion-Israel Institute of Technology
Haifa, 32000 (Israel)
Fax : (+972)48295703
E-mail: chr10zg@tx.technion.ac.il
[b] Prof. Dr. I. Goldberg
School of Chemistry, Tel Aviv University
Tel Aviv 69978 (Israel)
E-mail: goldberg@chemsg7.tau.ac.il
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201102348.
Chem. Eur. J. 2011, 17, 12294 – 12301
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Z. Gross, I. Goldberg and E. Rabinovich
Scheme 1. Synthesis of [(tpfcBr8)AuI
ACTHNUTRGEN(UNG PPh3)], obtained as a mixture of the N22 (2a) and N21 (2b) isomers.
ure 1b) were even more revealing. The ortho-F atoms of the
main isomer 2b are easily identified by the six major reso-
nances at around À135 ppm (accompanied by a similar set
for the minor isomer 2a), which proves that there is no
plane of symmetry in these complexes. The such obtained
information is fully consistent with the structures drawn in
Scheme 1, that is, the products have been assigned as (tri-
phenylphosphine)gold(I) complexes coordinated to mono-
ACHTUNGTRENNUNGanionic N21 and N22 corroles (note that two other N atoms
remains protonated). Confirmation of the above conclusion,
as well as confident assignment of the major isomer 2a as
the N22 coordinated isomer, was obtained via X-ray crystal-
lography performed on green-plate-like crystals obtained
from a benzene/heptanes solution (see below).
In contrast with analogous rhodium(I) corroles,[25] there
was no spontaneous oxidation of 2a/2b to the trivalent com-
plex in aerobic solution. The first attempt to obtain the cor-
responding gold
ACHTUNGTRENNUNG
solution of [(tpfcBr8)AuI
AHCTUNGTRENNUNG
tube (Scheme 2). There was an immediate change in color
from green to red, no evidence for coordinated triphenyl-
1
phosphine in the H NMR spectrum, and the 19F NMR spec-
trum changed from very complicated to very simple
(Figure 2). The 2:1 ratio of the ortho-F, para-F, and meta-F
resonances clearly pointed towards the presence of a C2
Figure 1. 1H NMR and 19F NMR spectra of [(tpfcBr8)AuI
[D8]toluene at 253 K.
ACHTUNGTRENNUNG(PPh3)] in
symmetry axis, consistent with expectation for the goldACHTUNTRGNEUNG(III)
corrole 3 (Scheme 2). However, only a minute amount of
the above mentioned product was obtained when the reac-
tion was carried out in (non-deuterated) toluene. Instead,
the two main products isolated after column chromatogra-
phy were 4a and 4b (in 25% and 30% yield, respectively),
identified as N21 and N22 benzyl-tpfcBr8, respectively, by
NMR (Figure 3). The 19F NMR spectra served to indicate
that the symmetry remained as low as in the reactants, while
zylic protons based on the previously reported N-benzyl de-
rivatives of the non-brominated corrole.[26] Both compounds
could be recrystallized from benzene/heptanes solution and
crystals of the N22 isomer provided good diffraction as to
allow for X-ray analysis and conformation of the proposed
structure (see below). No such products were obtained
1
the high field H resonances were safely assigned to N-ben-
Scheme 2. Reaction products obtained in the reactions of [(tpfcBr8)AuI
ACHTNUTRGNE(UNG PPh3)] (the mixture of 2b and 2a) with either Br2/toluene or NIS/toluene.
12296
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Gold(I) and GoldACHTUNGTRENNUNG(III) Corroles
FULL PAPER
for its structural elucidation. Complex 3 is stable in the solid
state and in anaerobic solutions for extended times, but
much less so in aerobic solutions and temperatures higher
than 408C.
On top of allowing for structural verification of the new
compounds, the three crystal structures obtained in this
study (Figure 4, Figure 5, Figure 6) provide a unique oppor-
Figure 2. 19F NMR spectrum of the gold
298 K.
ACHTUNGRTEN(NGNU III) corrole 3 in [D6]benzene at
Figure 4. ORTEP representation of the saddled N22-benzyl corrole 4b.
Ellipsoids are drawn at the 50% level of probability and H atoms are
omitted for clarity. a) Side view. b) Top view, with pentafluorophenyl
À
rings omitted for clarity. Selected bond length [ꢁ] and angles [8]: C43
N22 1.49(1), N22-C43-C44 113.4(9). Deviations from the plane defined
by the three non-substituted pyrrole nitrogen atoms [ꢁ]: N22: À0.38;
C43: À1.73. Torsion angles between the pyrrole rings: 36, 33.8, 11.2 and
À
À
À
À
158 for N21 N22, N22 N23, N23 N24, and N24 N21, respectively. Se-
lected bond length [ꢁ] and angles [8] for 5b: C38 N22 1.483(3), N22-
C38-C39 115.3(1). Deviations from the plane of the three non-substituted
À
pyrrole nitrogen atoms [ꢁ]: N22: À0.43; C38: À1.78. Torsion angles be-
À
À
tween the pyrrole rings: 34.1, 36, 4.5 and 10.18 for N21 N22, N22 N23,
À
À
N23 N24, and N24 N21, respectively.
tunity of gaining significant insight into several interesting
aspects of the fully brominated corrole macrocycle. In con-
trast with the low resolution (large R factor) structure of the
pyrrole-brominated corrole H3ACTHNUTRGNEUNG
(Br8tpfc) (1),[28] the structure
Figure 3. a) 1H NMR and b) 19F NMR spectra of N21 (4a) and N22 (4b)
of the N22-benzyl derivative 4b is of good quality (Figure 4,
R factor of 0.07) and enables a meaningful comparison with
the previously published analogue of the corresponding
non-brominated corrole, N22-benzyl-tpfc (5b).[25] The cor-
role macrocycle of 4b deviates severely from planarity pre-
dominantly due to the steric hindrance introduced by the
N22-benzyl arm. The deviation of the N22 atom from the
plane of the three non-substituted pyrrole nitrogen atoms is
however only 0.38 ꢁ for 4b, much less than the 0.43 ꢁ in
5b. The same trend is seen for the deviation of the methyl-
ene group and its two protons: these atoms are closer to the
corrole ring in 4b than in 5b. These observations may be ex-
plained by the core size of the corrole macrocycle, as reflect-
ed by the distances between the diagonally opposite nitro-
gen atoms, N21···N23 and N22···N24. The corresponding sep-
arations are systematically larger in the brominated deriva-
tive 4b (3.998 ꢁ and 3.861 ꢁ), than in the non-brominated
one 5b (3.993 ꢁ and 3.846 ꢁ). The electronegative with-
drawing bromines apparently increase the corrole core size
and thus enable a closer approach of the N-benzyl group to
benzyl-substituted corroles, respectively, in CDCl3 at 298 K.
when N-bromosuccinimide (NBS) or N-iodosuccinimide
(NIS) rather than Br2 were used. The optimal oxidizing
agent for converting [(tpfcBr8)AuI(PPh3)] to AuIII
ACTHNUTRGNENUG AHCUTNGTRENN(UGN tpfcBr8)
was found to be NIS, leading to 3 in an almost quantitative
yield. Alternatively, 3 could be obtained directly from 1 via
treatment with [ClAu
Scheme 3), a reagent reported for synthesis of gold
phyrins.[27] Recrystallization of the gold
(III) corrole from
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
CH2Cl2/hexane (1:2) or benzene/heptanes (1:2) solutions
provided red-plate-like X-ray quality crystals, which allowed
Scheme 3. Synthesis of (tpfcBr8)AuIII (3), directly from the free base 1.
Chem. Eur. J. 2011, 17, 12294 – 12301
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12297

Z. Gross, I. Goldberg and E. Rabinovich
the plane defined by the three
non-substituted pyrrole nitro-
gen atoms is very large (2.09
and
4.10 ꢁ,
respectively,
Figure 4). This may explain the
smaller hindrance inside the
macrocycle of 2b relative to
that in the other N-alkylated
derivatives (5b[27] and 4b),
which display much more
severe deformation of the cor-
role core as indicated by the
torsion angles between the dif-
ferent pyrrole rings (Figure 4).
The X-ray structure of 2b re-
veals a typical 1808 angle be-
tween the two ligands of the
Figure 5. ORTEP representation of the severely saddled N22 gold(I) complex 2b. Ellipsoids are drawn at the
50% level of probability and H atoms are omitted for clarity. a) Top view, with phenyl rings omitted for clarity.
À
À
b) Side view. Selected bond lengths [ꢁ] and angles [8]: Au N22 2.094(4), Au P 2.230(1), N22-Au-P 177.3(1).
Deviations from the plane of the three non-substituted pyrrole nitrogen atoms [ꢁ]: N22: À0.24; Au: À2.09; P:
À
À
À
À4.1. Torsion angles between the pyrrole rings: 26.7, 32.17, 19.4 and 10.98, for N21 N22, N22 N23, N23 N24,
À
and N24 N21, respectively.
gold(I)
moiety;
P-Au-N22
177.3(1)8. The deviation of the
N22 atom from the plane of the
three nonsubstituted pyrrole ni-
trogen atoms relatively to other
N-alkylated species is small:
0.24 ꢁ for 2b as opposed to
0.43 ꢁ and 0.38 ꢁ for 5b,[27]
and 4b, respectively. This small
deviation can be explained by
À
the
long
Au N22
bond
(2.094 ꢁ), as compared to other
Au N distances,[30] due to
strong trans influence of PPh3.
a
À
Figure 6. ORTEP representation of the almost perfectly planar (tpfcBr8)AuIII, 3. Ellipsoids are drawn at the
Complex
3 crystallized as
À
50% level of probability. Torsion angles between adjacent pyrrole rings: 1.01, 4.29, 2.9 and 1.398 for N21 N22,
¯
heptane solvate in a triclinic P1
space group (Figure 6). The
small torsion angles between
the adjacent pyrrole rings along
the ring—1.0, 4.3, 2.9, and
À
À
À
N22 N23, N23 N24, and N24 N21, respectively. Torsion angle between the macrocycle and the pentafluoro-
phenyl rings: 87.7, 89.78, and 84.858 for the C5, C10, and C15 positions, respectively. Selected bond lengths: 1.93
À
À
À
À
(2), 1.96 (2), 1.95 (2) and 1.94 (2) ꢁ, for Au N21, Au N22, Au N23, Au N24, respectively.
the core. These observations are consistent with earlier find-
ings that b-octabromination of meso-triarylcorrole deriva-
tives results in expansion of skeletal bond distances of the
corrole macrocycle.[29] In fact, the smaller core size of the
non-brominated corrole may be one of the reasons for its in-
ertness toward the reaction with the gold(I) precursor.
As can be easily seen from Figure 4 and Figure 5, there is
no symmetry element in the corrole derivatives that are N-
substituted by either a benzyl group (4b) or by gold(I)tri-
phenylphosphine (2b); that is, their symmetry is C1 and they
1.48—serve to illustrate the planarity of the macrocycle in
this structure. The pentafluorophenyl residues are practically
not twisted from the perpendicular orientation. The
Au atom displays only slightly distorted square-planar coor-
À
dination geometry, with the corresponding Au N bonds in 3
ranging from 1.93 to 1.98 ꢁ. This may be contrasted with
copper corroles (formally in a CuIII oxidation state), for
which metalACHTUNTRGENN(UG dx2Ày2)–corroleCAHTUNGTRENN(UGN p-HOMO) orbital interactions
were claimed to engender the copper(II) character to the
central ion and consequential saddling of the macrocycle.[18]
In our earlier studies of copper corrole complexes the 23-
atom corrole macrocycle was found to be significantly ruf-
fled,[19] a phenomenon that was later observed by a combi-
nation of X-ray crystallography and DFT calculations both
in the presence and in the absence of sterically hindered
substituents on the corrole periphery.[18,29] In structures eval-
À
¯
are chiral. Complex 2b crystallized in the triclinic P1 space
group, with two molecules of opposing chirality in an asym-
metric unit. The corrole macrocycle is nonplanar and exhib-
its a saddle-type conformation, with the pyrrole rings
around the circle being tilted up and down in an alternating
manner. The Au-PPh3 group is oriented edge-on with re-
spect to the molecular center, and the three pentafluoro-
phenyl groups are oriented roughly perpendicular to the cor-
role framework. As a result of the large ionic radius of
gold(I) (ca. 1.5 ꢁ), the deviations of Au and P atoms from
uated experimentally by crystallography the Cu NACHTUNGTRENNUNG(pyrrole)
bond length ranges were 1.89–1.90 ꢁ[18] and 1.87–1.89 ꢁ,[19]
considerably shorter than those observed in the gold
ACHTUNGTRENNUNG(III)
corrole 3. The lack of evidence for significant core deforma-
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Gold(I) and GoldACHTUNGTRENNUNG(III) Corroles
FULL PAPER
tion from planarity shared by gold
iridium
(III) corroles,[33] points towards more genuine oxida-
tion states and no strong metal(d) corrole(p) interaction
therein. For low-spin cobalt(III) ions (radius of 0.69 ꢁ is
G
E
phyrin complex (E1/2 =À0.56 V).[35] This suggests that the re-
duction of 3 may involve the metal and not the corrole, but
a more a definite assignment of the redox site is not yet pos-
sible because of the limited stability of the reduced species.
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
comparable to that of CuIII: 0.68 ꢁ) this may be attributed
to the difference in the energy levels of the respective dx2Ày2
orbitals. The chemistry of the IrIII and AuIII ions is affected,
on the other hand, by the outer f orbitals which shield the d-
electron shell. The latter two ions also have relatively large
ionic radii (0.82 and 0.85 ꢁ, respectively), and their insertion
into the corrole favors planar conformation and expanded
macrocyclic core. The diagonal N···N distances within the
macrocyclic core of 3 are 3.89 and 3.90 ꢁ, thus providing a
relaxed square-planar coordination environment for gold-
Preliminary photophysical investigations of the goldACHTUNGTRENNUNG(III)
corrole 3 revealed that it exhibits phosphorescence at room
temperature with an emission maximum at 769 nm
(Figure 8). A lifetime of (195Æ10) ms and a quantum yield
of 0.3% were obtained under a nitrogen atmosphere, while
the signal intensity diminished almost completely upon the
introduction of air. The room temperature quantum yield
and phosphorescence lifetime of 3 appear to be the highest
and longest, respectively, reported for any corrole derivative
so far.[36,37]
ACHTUNGTRENNUNG
hu and Ghosh,[34] the gold corroles obtained in our studies
are highly soluble in common organic solvents and their so-
lution properties could hence be confidently investigated.
The gold(I) complexes could not be reduced at reasonable
potentials, but displayed a semi-reversible redox process
with a half wave potential of 1.14 V. Spectroelectrochemical
studies revealed that the complex is destroyed upon continu-
ous oxidation at >1.2 V, which rules out electrochemical ox-
idation as a route to either gold(II) or goldACHTNUTRGNEUNG(III) corroles. It
is important to add that there is no mononuclear gold(I)
complex chelated by any other member of the porphyrinoid
family and a comparison could hence not be performed.
Cyclic voltammetry of the gold
sible redox process with a half-wave potential of À0.46 V
(Figure 7, inset). Spectroelectrochemical reduction of
ACHTUNGTNER(NUNG III) corrole revealed a rever-
Figure 8. Emission spectrum of the goldACHTNUTGRNEUNG(III) corrole 3 (lex =583 nm) in
toluene at 298 K, under a nitrogen atmosphere.
3
showed that the Soret band moves from 426 nm to 412 nm
(Figure 7) and that the Q bands also move to higher energy,
but the reduced species appeared to be not stable enough
for a thorough characterization. Nevertheless, we note that
the E1/2 for the reduction of 3 is more positive by more than
Conclusion
We have demonstrated the facile auration of corroles to
chiral gold(I) corroles, and their clean conversion to gold-
400 mV than that measured for the analogous galliumACTHUNTGRNEUNG(III)
corrole (Br8tpfc)Ga (it displays an irreversible reduction
ACHTUNGTREN(NUNG III) corroles, as well as a direct synthetic route to the latter.
with an Ipc of À1.29 V), but only by 100 mV relative to the
These new gold complexes, as well as the unexpected by-
products obtained by the reaction of the gold(I) corrole
with bromine, were fully characterized by NMR and X-ray
crystallography. We have also provided the first report of
the chemical, electrochemical, and photophysical properties
of gold corroles, including long wavelengths phosphores-
cence at room temperature. The advantageous utilization of
these features in aspects related to energy and human
health are currently investigated.
reported goldACHTUNGTRENNUNG(III)/gold(II) redox couple reported for a por-
Experimental Section
See the Supporting Information for full experimental details.
Synthesis of the gold(I) corroles, 2a and 2b: A 10 mL toluene solution of
1
(50 mg, 0.035 mmol) was treated with [MeAu
ACHTUNGRTENUN(NG PPh3)] (16 mg,
0.035 mmol) or [ClAu(PPh3)] at room temperature for 30 min, followed
AHCTUNGTRENNUNG
Figure 7. Cyclic voltammetry (inset) and spectroelectrochemistry (at
by silica-gel chromatography (silica gel, CH2Cl2/hexanes=1:10, as eluent)
purification. Recrystallization from CH2Cl2/pentane (1:10) provided
À0.6 V) of (tpfcBr8)AuIII in acetonitrile/0.1m TBABF4.
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Z. Gross, I. Goldberg and E. Rabinovich
green-plate-like crystals in 70% yield that contained a 1:4 ratio of 2a and
2b.
Compound 2a: 1H{31P} NMR (600 MHz, [D8]toluene, 232 K): d=6.49
ACHTUNGTRENNUNG
À136.99 (dd, J=7.63, 24.28 Hz, 1F), À137.38 (dd, J=7.63, 24.28 Hz, 1F),
À137.53 (dd, J=7.35, 23.90 Hz, 1F), À139.00 (dd, J=7.35, 23.90 Hz, 1F),
À139.47 (dd, J=6.43, 23.98 Hz, 1F), À140.81 (dd, J=6.52, 23.05 Hz, 1F),
À149.36 (t, J=21.12 Hz, 1F), À150.19 (t, J=21.12 Hz, 1F), À150.53 (t,
J=21.12 Hz, 1F), À162.17 (td, J=6.76, 21.52 Hz, 2F), À162.40 (td, J=
7.99, 22.75 Hz, 1F), À162.51 (td, J=8.61, 20.29 Hz, 1F), À162.60 (td, J=
7.99, 23.37 Hz, 1F), À162.80 (td, J=7.38, 23.37 Hz, 1F); UV/Vis
(CH2Cl2): lmax (eꢂ10À5)=465 (0.99), 610 (0.14), 700 nm (0.09).
(m, 6H), 6.27 (t, J=7.65 Hz, 3H), 5.17 (t, J=7.65 Hz, 6H), 0.67 (s, 1H),
À3.93 ppm (s, 1H); 19F NMR (565 MHz, [D8]toluene, 232 K): d=
À132.26 (d, J=21.60 Hz, 1F), À132.63 (d, J=21.60 Hz, 1F), À133.29 (d,
J=18.52 Hz, 1F), À133.87 (d, J=18.52 Hz, 1F), À134.02 (d. J=15.43 Hz,
1F), À135.47 (d, J=21.60 Hz, 1F), À146.57 (t, J=19.16 Hz, 1F), À146.91
(t, J=19.16 Hz, 1F), À147.58 ppm (t, J=19.16 Hz); 31P{1H} NMR
(243 MHz, [D8]toluene, 232 K): d=26.76 ppm; UV/Vis (toluene): lmax
(eꢂ10À5)=456 (0.92), 606 (0.16), 679 nm (0.13).
ACHTUNGTRENNUNG
Compound 2b: 1H{31P} NMR (600 MHz, [D8]toluene, 232 K): d=6.66 (t,
Acknowledgements
J=7.31 Hz, 3H), 6.53 (t, J=7.31 Hz, 6H), 5.18 (d, J=7.22 Hz, 6H),
À0.39 (s, 1H), À3.37 ppm (s, 1H); 19F NMR (565 MHz, [D8]toluene,
232 K): d=À131.86 (d, J=21.93 Hz, 1F), À133.17 (d, J=21.93 Hz, 1F),
À133.60 (d, J=21.93 Hz, 1F), À133.36 (d, J=21.93 Hz, 1F), À134.66 (d.
J=24.33 Hz, 1F), À136.90 (d, J=19.19 Hz, 1F), À146.26 (t, J=19.86 Hz,
1F), À147.16 (t, J=19.86 Hz, 1F), À147.31 (t, J=19.86 Hz, 1F), À158.49
(t, J=18.75 Hz, 1F), À158.64 (t, J=18.75 Hz, 1F), À158.81 (t, J=
18.75 Hz, 1F), À159.04 (t, J=18.75 Hz, 1F), À159.47 (t, J=18.75 Hz, 1F),
À159.69 ppm (t, J=18.75 Hz, 1F); 31P{1H} NMR (243 MHz, [D8]toluene,
232 K): d=28.61 ppm; UV/Vis (toluene): lmax (eꢂ10À5)=456 (0.92), 606
(0.16), 679 nm (0.13).
This research was supported by the DFG. We would like to thank Dr.
Michael Katz (Northwestern University) for his suggestion to use [ClAu-
AHCTUNGTERG(NNUN tht)] as an auration agent.
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Synthesis of the gold
ACHTUNGTRENNUNG
Method a) From 2a/2b:
A
0.025 mmol) was added dropwise to a 5 mL toluene solution of 2a/2b
(20 mg, 0.01 mmol) and the reaction mixture was stirred at room temper-
ature for 30 min, after which the reaction was quenched by 15 mL of
H2O. Extraction with CH2Cl2 was followed by addition of hexane and 3
was precipitated at 48C as a red powder in 95% yield (16 mg).
Method b) Directly from 1: [ClAuACHTNUTRGNE(UNG tht)] (10 mg, 0.03 mmol) was added to
a solution of 1 (12 mg, 0.008 mmol) in chloroform (10 mL) containing
few drops of pyridine. The solution was stirred at room temperature for
30 min under nitrogen atmosphere. The product was purified by neutral
alumina chromatography (hexane as an eluent) with a 88% yield. Re-
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tions provided red-plate-like crystals. 19F NMR (376.75 MHz, C6D6): d=
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À136.70 (dd, J1FÀF =7.54 Hz, J2FÀF =24.52 Hz, 2F), À137.41 (dd, J3
=
FÀF
7.78 Hz, J4FÀF =24.33 Hz, 4H), À150.37 (t, J4FÀF =22.46 Hz, 2F), À150.78
(t, J2FÀF =21.33 Hz, 1F), À162.65 (td, J3FÀF =7.41 Hz, J4FÀF =23.58 Hz,
4F), À163.10 (td, J1FÀF =7.41 Hz, J2FÀF =22.23 Hz, 2F); UV/Vis (toluene):
lmax (eꢂ10À5)=428 (1.11), 543 (0.11), 580 nm (0.368); MS (MALDI
TOF LDÀ): m/z (typical cluster due to multiple Br isotopes): centered at
1620.00.
Synthesis of 4a and 4b: [(tpfcBr8)AuACHTNUGRTENUNG(PPh3)], 2, was dissolved in toluene
and excess of Br2 was added. The resulting solution was stirred at room
temperature till all the starting material was consumed. Monitoring of
the reaction was carried with TLC plates (hexanes/CH2Cl2 =1:2). The
products, 4a and 4b, were purified by silica-gel chromatography (silica
gel, CH2Cl2/hexanes=1:100, as eluent). The product 4b was recrystallized
from a benzene/heptane (1:2) solution to give green needle like crystals
in 30% yield.
Compound 4a: 1H NMR (400 MHz, C6D6): d=6.56 (t, J=7.49 Hz, 1H),
6.36 (t, J=7.49 Hz, 2H), 4.70 (d, J=7.28 Hz, 2H), À1.94 (d, J=14.08 Hz,
1H), À2.54 (d, J=14.08 Hz, 1H); 19F NMR (376.75 MHz, C6D6): d=
À136.93 (dd, J=7.74, 24.38 Hz, 1F), À137.28 (dd, J=7.74, 24.38 Hz, 1F),
À137.86 (dd, J=7.52, 24.45 Hz, 1F), À138.23 (dd, J=7.96, 24.45 Hz, 1F),
À139.98 (dd, J=7.34, 23.61 Hz, 1F), À140.18 (dd, J=6.29, 23.61 Hz, 1F),
À149.37 (t, J=19.76 Hz, 1F), À150.65 (t, J=21.28 Hz, 1F), À150.85 (t,
J=21.79 Hz, 1F), À161.75 (td, J=8.70, J=23.20 Hz, 1F), À161.91 (td, J=
7.73, 23.20 Hz, 1F), À162.26 (td, J=8.70, 23.20 Hz, 1F), À162.58 (td, J=
7.73, 23.20 Hz, 1F), À162.71 (td, J=7.73, 23.20 Hz, 1F-162.87 (td, J=7.73,
23.20 Hz, 1F); UV/Vis (CH2Cl2): lmax (eꢂ10À5)=446 (0.99), 616 nm
(0.34).
Compound 4b: 1H NMR (400 MHz, C6D6,): d=6.51 (t, J=7.48 Hz, 1H),
6.34 (t, J=7.71 Hz, 2H), 4.40 (d, J=7.43 Hz, 2H), À3.23 (d, J=14.92 Hz,
1H), À3.85 (d, J=14.92 Hz, 1H); 19F NMR (376.75 MHz, C6D6): d=
12300
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Gold(I) and GoldACHTUNGTRENNUNG(III) Corroles
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Published online: October 4, 2011
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