Synthesis, stability, and reactivity of [(TPA)Zn(SH)]+ in aqueous and organic solutions

Article abstract of DOI:10.1002/ejic.201100527

Reaction of the complex [(TPA)Zn(H₂O)]²⁺ [TPA = tris(2-pyridylmethyl)amine] with hydrogen sulfide in aqueous buffered solution gives the corresponding monomeric hydrogensulfido complex [(TPA)Zn(SH)] ⁺, which was fully characterized, including by XRD. This complex is stable at neutral pH, but decomposes under basic conditions to yield the free ligand and zinc sulfide, and under acidic conditions to give hydrogen sulfide and the starting aqua complex. In organic solvents, the coordinated sulfur atom reacts with electrophiles such as methylmethanethiosulfonate to yield methyltrisulfide. Reaction with the hydroxo complex [(Tp^Ph,Me)Zn(OH)] [Tp^Ph,Me = hydridotris{(5-methyl-3-phenyl)pyrazolyl}borate] promotes the formation of the unsymmetrical dinuclear μ-sulfido species [(TPA)Zn-S-Zn(Tp^Ph,Me)]⁺, which, upon treatment with one molar equivalent of trifluoroacetic acid, dissociates into [(Tp ^Ph,Me)Zn(SH)] and [(TPA)Zn(CF₃CO₂)] ⁺, resulting in the transfer of the hydrogensulfido ligand from one zinc center to another.

Full text of DOI:10.1002/ejic.201100527

FULL PAPER
DOI: 10.1002/ejic.201100527
Synthesis, Stability, and Reactivity of [(TPA)Zn(SH)]+ in Aqueous and
Organic Solutions
Erwan Galardon,*[a] Alain Tomas,[b] Pascal Roussel,[c] and Isabelle Artaud[a]
Keywords: Zinc / Sulfur / N ligands / Hydrogen sulfido ligand
Reaction of the complex [(TPA)Zn(H2O)]2+ [TPA = tris(2-pyr-
idylmethyl)amine] with hydrogen sulfide in aqueous buff-
philes such as methylmethanethiosulfonate to yield methyl-
trisulfide. Reaction with the hydroxo complex [(TpPh,Me)-
ered solution gives the corresponding monomeric hydro- Zn(OH)] [TpPh,Me = hydridotris{(5-methyl-3-phenyl)pyrazo-
gensulfido complex [(TPA)Zn(SH)]+, which was fully charac-
terized, including by XRD. This complex is stable at neutral
pH, but decomposes under basic conditions to yield the free
ligand and zinc sulfide, and under acidic conditions to give
hydrogen sulfide and the starting aqua complex. In organic
solvents, the coordinated sulfur atom reacts with electro-
lyl}borate] promotes the formation of the unsymmetrical di-
nuclear μ-sulfido species [(TPA)Zn–S–Zn(TpPh,Me)]+, which,
upon treatment with one molar equivalent of trifluoroacetic
acid, dissociates into [(TpPh,Me)Zn(SH)] and [(TPA)Zn-
(CF3CO2)]+, resulting in the transfer of the hydrogensulfido
ligand from one zinc center to another.
gen sulfide to hydrogen,[6] whereas bioinorganic studies are
more scarce and focus on the interaction of hydrogen sulf-
ide with hemoproteins.[7]
Introduction
Hydrogen sulfide (H2S) is well known to be a major
player in the metabolism of exotic organisms as a source of
electrons or as the final product in the reduction of oxidized
sulfur derivatives.[1] It has also emerged as a new gaso-
transmitter in mammals, along with nitric oxide and carbon
monoxide. In living organisms, H2S can react with several
hemoproteins, such as haemoglobin, which can be con-
verted to sulfhaemoglobin,[2] or cytochrome c oxidase,
which has been proposed as a biomarker for H2S expo-
sure.[3] Apart from iron, zinc is also known to interact with
hydrogen sulfide in biological systems. For instance, HS–
strongly inhibits isoforms of carbonic anhydrase,[4] and zinc
has been proposed to be closely associated to sulfide bind-
ing and transport in some chemoautotrophic organisms.[5]
However, the coordination chemistry of hydrogen sulfide
has been essentially directed towards organometallic chem-
istry so far, with a strong interest in hydrodesulfurization
processes (removal of sulfur from natural gas and refined
petroleum products) and the catalytic conversion of hydro-
We, and others, have isolated hydrogensulfido zinc deriv-
atives, either by direct reaction of a hydroxo derivative with
hydrogen sulfide,[8] or as the end product of the reaction
between an alkyldisulfanido complex and a thiolate in apo-
lar aprotic solvents.[9] To date, isolation of stable hydro-
gensulfido zinc complexes has required bulky apolar li-
gands, based either on substituted hydridotris(pyrazolylbor-
ate)[8a,9,10] or hydridotris(thioimidazolyl)borate,[11] and
using azamacrocyclic ligands only led to degradation.[12]
Because hydrogen sulfide exists in three different forms
(H2S, HS–, and S2–), which can potentially bind transition
metals, its biological properties involving interaction with a
metal center are dependent on the presence of protons in
the local environment. Here, we report that with a simple
scaffold, such as tris(2-pyridylmethyl)amine (TPA, Fig-
ure 1), a stable hydrogensulfido zinc complex can be formed
in aqueous buffered solution as well as in organic solvents.
[a] Laboratoire de Chimie et Biochimie Pharmacologiques et
Toxicologiques, UMR 8601 CNRS, Université Paris Descartes,
45 rue des Saints Pères, 75270 Paris cedex 06, France
Fax: +33-1-42864050
E-mail: erwan.galardon@parisdescartes.fr
[b] Laboratoire de Cristallographie et RMN Biologiques, UMR
8015 CNRS, Université Paris Descartes,
4 avenue de l’Observatoire, 75270 Paris cedex 06, France
[c] UCCS – Unité de Catalyse et Chimie du Solide, UMR 8012
CNRS, École Nationale Supérieure de Chimie de Lille
B. P. 90108, 59652 Villeneuve d’Ascq cedex, France
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201100527.
Figure 1. Ligands used or cited in this work.
Eur. J. Inorg. Chem. 2011, 3797–3801
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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E. Galardon, A. Tomas, P. Roussel, I. Artaud
FULL PAPER
The stability of the complex and its reactivity towards oxid- The Zn–S bond is the longest reported for hydrogensulfido
ized sulfur species and other zinc complexes is also dis- zinc derivatives, probably because the metal is in a N3S en-
cussed.
vironment in the other complexes.[8a,9,10] However, it is
within the range of reported Zn–S distances for N4S thio-
late containing complexes.[12,15] As in the other hydro-
gensulfido zinc derivatives, no ν(SH) is observed by IR
spectroscopy.
Results and Discussion
Formation and Stability of the Hydrogensulfido Complex in
Aqueous Solution
Mixing TPA with one equivalent of hydrated zinc nitrate
in
4-(2-hydroxyethyl)-1-piperazineethanesulfonic
acid
(HEPES) buffer affords the corresponding aqua complex
[(TPA)Zn(H2O)](NO3)2 [1(NO3)2],[13] the reactivity of
which can be easily monitored by 1H NMR spectroscopy.[14]
Indeed, addition of KSH to a buffered solution of 1-
(NO3)2 in HEPES (50 mm, pH = 7.1) results in a clear shift
of the ortho-H of the pyridine moieties from 8.62 to
8.76 ppm after addition of 1 equiv. of KSH (see Figure 2),
indicating the formation of a new species 2(NO3). However,
addition of more than one equivalent of hydrogen sulfide
leads to the appearance of signals of free TPA (Figure 2)
along with the precipitation of zinc sulfide.
Figure 3. ORTEP view of complex 1(BPh4) showing thermal ellip-
soids at 50% probability and atom labeling. Hydrogen atoms and
the BPh4 anion have been omitted for clarity. Selected bond lengths
[Å] and angles [°]: Zn1–N1 2.0985, Zn1–N2 2.114, Zn1–N3 2.1169,
Zn1–N4 2.2968, Zn1–S1 2.3060, N1–Zn1–N2 113.92, N2–Zn1–N3
115.94, N1–Zn1–N3 112.69, N1–Zn1–S1 104.91, N2–Zn1–S1
102.26, N3–Zn1–S1 105.45, N4–Zn1–S1 178.17, N1–Zn1–N4
75.78, N2–Zn1–N4 75.92, N3–Zn1–N4 75.69.
Stability of 2 in Aqueous Solution
Once formed, the hydrogensulfido complex 2(NO3) is
stable in aqueous solution for days. Although the affinity
constant between the zinc complex and HS– could not be
directly deduced from the NMR spectroscopic data,[16]
a
Kapp value has been evaluated by competition experiments
with sodium phenyl phosphate, a substrate of known affin-
ity,[14] and was found in the same order (logKapp
3.9Ϯ0.2).
=
This behavior is different under acidic or basic condi-
tions (Scheme 1). On addition of one equivalent of perchlo-
ric acid to a solution of 2(ClO4) in a 1:9 mixture of [D6]-
Figure 2. Aromatic region of the 1H NMR spectra recorded at
500 MHz of complex 1(NO3)2 (4 mm in HEPES buffer 50 mm, pH
= 7.1) after addition of 0 (a), 0.25 (b), 0.50 (c), 0.75 (d), 1.00 (e),
1.25 (f), and 2.00 (g) equiv. of KSH. * indicates the signals from
the free ligand TPA.
1
DMSO and D2O, the H NMR spectrum reverts back to
the spectrum of the aqua derivative, indicating that the re-
sulting [(TPA)Zn(SH2)]2+ complex is not stable, which leads
to the subsequent release of H2S in solution (see Figure S1
in the Supporting Information). Similarly, under the same
conditions, addition of one equivalent of sodium hydroxide
to 2(ClO4) leads to the release of the TPA ligand in solution
as the major identified process (75%), with concomitant
precipitation of zinc sulfide (Figure S2). This is in accord-
ance with the reported instability of hydrogensulfido zinc
derivatives in the presence of strong bases in organic sol-
vents.[8b]
The new complex 2(NO3) has been characterized by mass
spectrometry and NMR spectroscopy. It shows a peak at
m/z = 387 (100%) by ESI+-MS, corresponding to [(TPA)-
1
Zn(SH)]+. Its H NMR spectrum, recorded in H2O instead
of D2O, shows a typical signal at –0.86 ppm integrating for
one proton assigned to the SH proton, as in previous hydro-
gensulfido zinc complexes.[8b,9] We also separately synthe-
sized 2(ClO4) by reaction of TPA, Zn(ClO4)2·6H2O, and
KSH in methanol. This complex was obtained as analyti-
1
cally pure microcrystals, and it displays the same H NMR
and MS spectra as 2(NO3). For full characterization, we
exchanged the perchlorate anion to a tetraphenylborate
anion, which yielded crystals suitable for XRD analysis.
The ORTEP view of 2(BPh4) is displayed in Figure 3 and
shows a mononuclear complex in which the zinc center is
in a slightly distorted trigonal bipyramidal N4S geometry. Scheme 1. Stability of 2 in aqueous solution.
3798 Eur. J. Inorg. Chem. 2011, 3797–3801
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Synthesis and Study of [(TPA)Zn(SH)]+ in Solution
Reactivity of the 2 towards Electrophiles or Other Zinc
Complexes in Organic Solvents
[TpCum,Me = hydridotris{(3-p-cumenyl-5-methyl)pyrazolyl}-
borate] reported by Vahrenkamp et al., which was obtained
by thermal condensation of the corresponding hydrogen-
sulfido derivatives.[8a,18]
Our previous study on the reactivity of the hydrogen-
sulfido zinc complex TpiPr,iPrZn(SH) [TpiPr,iPr = hydridotris-
{(3,5-isopropyl)pyrazolyl}borate] was hampered by its lack
of solubility in polar solvents.[9] In contrast 2(ClO4) is solu-
ble in CH2Cl2 and DMSO, and its reactivity could be more
thoroughly investigated. Although the outcome of the reac-
tion between 2(ClO4) and the thiosulfonate MeS–SO2Me
(Scheme 2 and Figure S3) is not affected by the solvent,
replacing CH2Cl2 with DMSO in the reaction with the less
reactive sulfenylthiocarbonate PhCH2S–SCO2Me has a
dramatic impact. Indeed, there is no reaction in CH2Cl2
between 2(ClO4) and 2 equiv. of PhCH2S–SCO2Me [a result
that recalls our previous work with TpiPr,iPrZn(SH)].[9]
However, 2(ClO4) quickly reacts in DMSO to quantitatively
yield the corresponding trisulfide (PhCH2S)2S.
This new species is sensitive to traces of acid, and ad-
dition of one equivalent of trifluoroacetic acid to 4 leads to
the formation of a 1:1 mixture of [(TPA)Zn(CF3CO2)]+ (5)
(see Figure S6 and Exp. Sect.) and of the known hydro-
gensulfido complex TpPh,MeZn(SH) (6).[8b] The striking
selectivity in favor of the formation of 6 can be rationalized
on the basis of a higher affinity of the N3Zn site than the
N4Zn one for the anionic hydrogensulfido ligand, a result
that is in agreement with the shorter Zn–S distance ob-
served in 6[8b] than 2. Complex 6 has already been described
as a thermodynamic sink in previous studies.[8b,9]
Thus, the transfer of the hydrogensulfido ligand from one
metal center to another is possible through the formation
of a μ-sulfido dinuclear species (Scheme 3).
Scheme 2. Reactivity of 2 with MeS–SO2Me.
As detailed above, the stability of 2 in aerated aqueous
buffer or organic solvents suggests a tight binding of the
hydrogensulfido group to the metal center, precluding a
simple exchange with another complex in solution. How-
ever, the transfer of the hydrogensulfido ligand from one
zinc center to another metallic center is an attractive target
that maybe relevant in the sulfide binding to the tubeworm
hemoglobin reported by Flores et al.,[5] and we anticipated
that it could take place by the formation of a dinuclear μ-
sulfido derivative. In this regard, we used a strategy that we
had previously used to isolate alkyldisulfanido complexes
from the corresponding hydrodisulfide,[9] which are, like
complex 2, sensitive to basic conditions. Indeed, reaction of
[(TpPh,Me)Zn(OH)][17] [TpPh,Me = hydridotris{(5-methyl-3-
phenyl)pyrazolyl}borate] with one molar equivalent of
2(ClO4) or 2(BPh4) in a mixture of acetone and CH2Cl2,
gave rise to the formation of a new product identified as
[(TPA)Zn–S–Zn(TpPh,Me)]+ (4) by MS and NMR spec-
troscopy, as well as elemental analysis. The mass spectrum
(Figure S4) of the crude mixture displays a peak at m/z =
937 (ESI+, 100%), with the isotopic pattern expected for the
dinuclear cation of 4. This structure is further confirmed by
NMR spectroscopy. The aromatic protons at the 5-position
of the pyrazolyl groups are strongly shifted upfield relative
to those of the mononuclear species, a feature observed in
all dinuclear zinc derivatives bearing aromatic groups on a
Scheme 3. Reactions leading to hydrogensulfido transfer from one
zinc center to the other.
Conclusions
We have shown that in aqueous buffered solution hydro-
gen sulfide binds the zinc center of the complex [(TPA)-
Zn(H2O)]2+ strongly to give the corresponding monomeric
hydrogensulfido complex [(TPA)Zn(SH)]+ (2). Regarding
the possible role of zinc in the sulfide binding in hydrother-
mal vent tubeworms, we have identified two possible path-
ways leading to the cleavage of the zinc–sulfur bond: i) hy-
drogen sulfide can be released in solution in acidic media;
ii) more interestingly, the hydrogensulfido ligand can be
transferred to a zinc center of higher affinity through the
intermediate formation of a μ-sulfido dinuclear species.
This transfer can be very selective as the relative affinities
of the two cations for HS– are markedly different. More-
over, the requirement of only one equivalent of an acid sup-
ports the idea that this transfer could be regulated by the
local proton environment in biological systems.
1
Tp backbone.[8a] Furthermore, the H1H NOESY experi-
Experimental Section
ment shows that the two ligands TPA and Tp are in close
proximity (Figure S5). Finally, this dinuclear structure is
also in accordance with the elemental analysis obtained for
4(BPh4). To the best of our knowledge, 4 is the first non-
symmetrical μ-sulfido zinc species reported. The only other
1
General: H NMR spectra were recorded at 300 K with a Bruker
ARX-250 spectrometer or at 500 MHz with an AVANCE II-500
spectrometer and chemical shifts are calibrated by the residual sol-
vent peak.[19] Elemental analyses were carried out by the micro-
noncluster
example
is
TpCum,MeZn–S–ZnTpCum,Me analysis service at Gif-sur-Yvette CNRS. Solvents were distilled
Eur. J. Inorg. Chem. 2011, 3797–3801
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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3799

E. Galardon, A. Tomas, P. Roussel, I. Artaud
FULL PAPER
using standard procedures. Chemicals were purchased from Aldrich
or Acros and used as received. TPA, TpPh,MeZn(OH), and potas-
sium hydrosulfide were synthesized as described previously.[17,18,20]
Deuterated HEPES buffer was prepared by dissolving HEPES free
acid in D2O and adjusting the pH with NaOD.
terated HEPES buffer (5 mL, 50 mm, pH = 7.1). A portion of this
solution (200 μL) was added to deuterated buffer (300 μL) in an
NMR tube to make a 4 mmol solution of 1(NO3)2, and a solution
of KSH in deuterated HEPES buffer was added.
Competitive 1H NMR Titration Experiment with Sodium Phenyl
Phosphate:[14] To a solution of 1(NO3)2 in HEPES buffer were
added two equiv. of sodium phenyl phosphate, then increasing
[(TPA)Zn(SH)]ClO4 [2(ClO4)]: TPA (500 mg, 1.72 mmol) and
Zn(ClO4)2·6H2O (641 mg, 1.72 mmol) were stirred for 5 min in
methanol (20 mL) at room temp. KSH (124 mg, 1.72 mmol) was amounts of KSH in a buffer solution. The reverse reaction, in
added, and the reaction mixture stirred for 1 h. After filtration of
the slightly yellow precipitate, the organic phase was concentrated
and left to stand at room temp., to give yellow crystals of 2(ClO4)
which two equiv. of KSH were added to 1(NO3)2 and then increas-
ing amounts of Na2PP added was also performed. Fitting of the
NMR spectroscopic data gave an equilibrium constant Kapp
=
2.0Ϯ0.2 for the equation: [(TPA)Zn(PP)] + HS– = [(TPA)Zn-
1
3
(320 mg, 38%). H NMR (DMSO): δ = 8.91 (d, JH,H = 4.8 Hz, 3
H), 8.13 (t, 3JH,H = 7.7 Hz, 3 H), 7.68 (m, 6 H), 4.22 (s, 6 H), –1.37
(SH)]+ + PP2–.
(s,
1
H) ppm. MS (ESI+): 387 [100%, {(TPA)Zn(SH)}+].
Reactivity Studies of 2(ClO4): to a solution of 2(ClO4) (400 μL,
15 mm) in DMSO was added the corresponding reactants. The pro-
C18H19ClN4O4SZn·0.5H2O (504.97): calcd. C 68.73, H 5.06, N
9.82; found C 68.42, H 5.17, N 9.69. The perchlorate anion was
further exchanged for a tetraphenylborate by mixing equimolar
amounts of 2(ClO4) and NaBPh4 in methanol for 1 h, followed by
filtration. Crystal suitable for XRD analysis were grown from a
CH2Cl2/heptane mixture.
1
gress of the reaction was monitored by H NMR spectroscopy.
X-ray Data Collection and Structural Determination: Data collec-
tion on 2(BPh4) was performed with monochromated Mo-Kα radia-
tion (λ = 0.71073 Å) with a Nonius Kappa detector at 293 K, using
the HKL package for data collection and reduction.[21] Triclinic
[(TPA)Zn(SO2Me)]BPh4 [3(BPh4)]: TPA (70 mg, 0.24 mmol) and
Zn(ClO4)2·6H2O (90 mg, 0.24 mmol) were stirred for 5 min in
methanol (3 mL) at room temp. MeSO2Na (32 mg, 0.26 mmol) was
added, and the reaction mixture stirred for 30 min. After filtration
of the precipitate, a solution of NaBPh4 (82 mg) in methanol
(2 mL) was added and the slurry was stirred for 15 min. After fil-
tration, 3(BPh4) was obtained as a pale yellow powder (125 mg,
unit cell parameters:
a = 9.5319(9), b = 20.0933(18), c =
21.3640(19) Å, α = 82.238(2), β = 83.042(2) γ = 79.536(2)°, V =
3967.2(6) Å3, Z = 2 and d(calc) = 1.182 mgm3, yielded 21035 total
reflections to a 2θ max = 58.44°. The structure was solved by direct
methods in the space group P1 using SHELXS-97
[22]
¯
and refined
by least-squares methods on F2 using SHELXL-97.[23] Non-hydro-
gen atoms were refined with anisotropic thermal parameters. Hy-
drogen atoms were placed in their geometrically generated posi-
tions and were allowed to ride on their parent atom with an iso-
tropic thermal parameter 1.2 times of those of the attached atoms.
H atoms attached to S atoms were refined with an isotropic tem-
perature factor. For all 21035 unique reflections and 889 variables,
the final anisotropic full-matrix least-squares refinement on F2 at
R1 = 0.0451 and wR2 = 0.1293 with a goodness of fit (Gof) of
1.081. In the final cycles of refinements, the peak pattern of elec-
tron density suggested that part of solvent was highly disordered;
attempts to model this disorder were unsuccessful. In the final cy-
cles of refinement, the contribution to electron density correspond-
ing to the disordered solvent was removed from the observed data
using the SQUEEZE option in PLATON.[24] The resulting data
vastly improved the precision of the geometric parameters for the
remaining structure.
1
3
69%). H NMR (DMSO): δ = 8.95 (d, JH,H = 4.7 Hz, 3 H), 8.04
3
3
(t, JH,H = 7.9 Hz, 3 H), 7.61 (m, 3 H), 7.55 (d, JH,H = 7.9 Hz, 3
3
3
H), 7.18 (m, 8 H), 6.92 (t, JH,H = 7.3 Hz, 8 H), 6.79 (t, JH,H
7.3 Hz, 4 H), 4.31 (s, 6 H), 2.47 (s, 3 H) ppm. MS (ESI+): 433
[50%, C43H41BN4O2SZn·0.7NaClO4
{(TPA)Zn(SO2Me)}+].
=
(839.39): calcd. C 61.50, H 4.92, N 6.67; found C 61.48, H 5.04, N
6.50.
[(TPA)Zn-S-Zn(TpPh,Me)]BPh4 [4(BPh4)]: Complex 3·BPh4 (45 mg,
0.06 mmol) was dissolved in distilled acetone (3 mL) and added at
0 °C to a solution of TpPh,MeZn(OH) (36 mg) in distilled CH2Cl2
(1.5 mL). The mixture was stirred for 30 min, concentrated, and a
white powder obtained after addition of pentane (51 mg, 60%). 1H
3
NMR ([D6]acetone): δ = 9.10 (d, JH-H = 5.1 Hz, 3 H, HTPA), 8.02
3
4
(dt, JH,H = 7.6, JH,H = 1.5 Hz, 3 H, HTPA), 7.8 (m, 6 H, HTp),
3
7.51 (d, JH,H = 7.6 Hz, 3 H, HTPA), 7.37 (m, 11 H, HTPA, HBPh4),
3
6.93 (t, JH,H = 7.1 Hz, 8 H, HBPh4), 6.88 (m, 9 H, HTp), 6.78 (t,
CCDC-817629 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
3JH,H = 7.1 Hz, 4 H, HBPh4), 6.33 (s, 3 H, HTp), 4.02 (s, 6 H, HTPA),
2.68 (s, 9H HTp) ppm. MS (ESI+): 937 [100%, {(TPA)Zn–S–
Zn(TpPh,Me)}+]. C72H66B2N10SZn2·1.5H2O (1282.36): calcd.
C
67.41, H 5.42, N 10.52; found C 67.46, H 5.29, N 10.92.
Supporting Information (see footnote on the first page of this arti-
cle): Figures S1–S6 and crystallographic data for 2(BPh4).
[(TPA)Zn(CO2CF3)]BPh4 [5(BPh4)]: TPA (70 mg, 0.24 mmol) and
Zn(ClO4)2·6H2O (90 mg, 0.24 mmol) were stirred for 5 min in
methanol (3 mL) at room temp. CF3CO2Na (36 mg, 0.26 mmol)
was added, and the reaction mixture stirred for 30 min. After fil-
tration of the precipitate, a solution of of NaBPh4 (82 mg) in meth-
anol (2 mL) was added and the slurry was stirred for 15 min. After
filtration, 5(BPh4) was obtained as a white powder (117 mg, 62%).
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3
1H NMR (DMSO): δ = 8.67 (d, JH,H = 5.1 Hz, 3 H), 8.00 (dt,
4
3
3JH,H = 7.8, JH,H = 1.5 Hz, 3 H), 7.56 (m, 3 H), 7.52 (d, JH,H
=
3
7.8 Hz, 3 H), 7.18 (m, 8 H), 6.93 (t, JH,H = 7.3 Hz, 8 H), 6.79 (t,
3JH,H = 7.3 Hz, 4 H), 4.40 (s, 6 H) ppm. MS (ESI+): 467 [100%,
{(TPA)Zn(CO2CF3)}+]. C44H38BF3N4O2Zn·H2O (805.71): calcd. C
65.57, H 5.00, N 7.07; Found C 65.51, H 4.86, N 6.94.
1H NMR Experiments with 1(NO3)2:[13] Zn(NO3)2·6H2O (14.9 mg,
0.05 mmol) and TPA (14.5 mg, 0.05 mmol) were dissolved in deu-
3800
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Synthesis and Study of [(TPA)Zn(SH)]+ in Solution
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