Sulfur transfer reactions of a zinc tetrasulfanido complex

Article abstract of DOI:10.1039/d0dt01384f

A zinc tetrasulfanido complex supported by a bis(carboxamide)pyridine ligand framework has been synthesized by the insertion of elemental sulfur into the zinc-S(thiolate) bond of a zinc dithiolate complex ([LZn]2-). This paper reports on sulfur transfer reactions of this polysulfanido complex ([1]2-) and compares this behavior to known reactions of metal polysulfido complexes. Complex [1]2- was demonstrated to be in exchange with [LZn]2- and free elemental sulfur in solution. Although triphenylphosphine abstracts sulfur from [1]2- to form [LZn]2-, complex [LZn]2- can abstract sulfur from the zinc polysulfido complex (TMEDA)ZnS6 (TMEDA = N,N,N′,N′-tetramethylethylenediamine). The tetrasulfanido complex [1]2- can also transfer sulfur to dimethyl acetylenedicarboxylate to form a zinc dithiolene complex. These studies demonstrate that the zinc complex with a tetrasulfanido moiety can undergo similar reactions as metal complexes with purely inorganic polysulfido groups, although the final metal-containing products are different.

Full text of DOI:10.1039/d0dt01384f

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Sulfur Transfer Reactions of a Zinc Tetrasulfanido Complex
Moises Ballesteros II and Emily Y. Tsui*
Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana
46556, United States
Abstract
A zinc tetrasulfanido complex supported by a bis(carboxamide)pyridine ligand framework has
been synthesized by the insertion of elemental sulfur into the zinc‒S(thiolate) bond of a zinc
dithiolate complex ([LZn]2‒). This paper reports on sulfur transfer reactions of this polysulfanido
complex ([1]2−) and compares this behavior to known reactions of metal polysulfido complexes.
Complex [1]2‒ was demonstrated to be in exchange with [LZn]2‒ and free elemental sulfur in
solution. Although triphenylphosphine abstracts sulfur from [1]2− to form [LZn]2−, complex [LZn]2−
can abstract sulfur from the zinc polysulfido complex (TMEDA)ZnS6 (TMEDA = N,N,N',N'-
tetramethylethylenediamine). The tetrasulfanido complex [1]2‒ can also transfer sulfur to dimethyl
acetylenedicarboxylate to form a zinc dithiolene complex. These studies demonstrate that the
zinc complex with a tetrasulfanido moiety can undergo similar reactions as metal complexes with
purely inorganic polysulfido groups, although the final metal-containing products are different.
Introduction
Transition metal polysulfido complexes (LnMSx, Fig. 1 left) have been extensively studied as
intermediates in the synthesis of metal sulfide materials and as structural analogs of biological
active sites.1-3 These compounds are typically synthesized by the addition of elemental sulfur or
anionic polysulfides to a metal precursor, and examples with metals including titanium, nickel,
copper, and zinc, among others, have been prepared and structurally characterized.4-7 The
rearrangement of metal-bound polysulfido moieties is facile, permitting great diversity in the
structure of such complexes.6,8,9 The reactivity of metal polysulfido complexes is also well
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explored. For example, metal polysulfido complexes have been shown to undergo catenation
readily to form new polysulfido complexes.10,11 These species can also transfer sulfur atoms to
chalcogens and phosphines, and perform nucleophilic attack on electron-poor alkenes and
alkynes.4,12-15 Sulfur-atom abstraction from metal polysulfido complexes to form shorter-chain
polysulfide moieties has also been demonstrated.13 Altogether, compounds in this class serve as
useful precursors to a number of molecules and materials of fundamental interest.
Figure 1 compares the structure of polysulfido complexes with that of polysulfanido
complexes, a class of compounds whose reactivity has been far less studied. Although there are
numerous examples of metal persulfido complexes (persulfido = RSS−), there are few reported
examples of complexes containing polysulfanido moieties (R(S)xS−, x > 1).16-18 While it is
hypothesized that persulfides are more nucleophilic than their corresponding thiolates, the effect
of additional sulfur atoms on nucleophilicity and sulfur transfer behavior is not well known.19
Nevertheless, the reactivity of metal polysulfanido complexes presents an interesting target of
study, as these species may be relevant as models of species formed during biological sulfur
redox signaling processes.19 Further, in comparison to metal polysulfido complexes, which can
thermally degrade into species of higher nuclearity or to heterogeneous metal sulfide materials
upon sulfur transfer,6,20 polysulfanido complexes may potentially act as reversible homogeneous
sulfur transfer agents by regeneration of the metal thiolate precursor.
S
S
S
(S)x
(S)x
R
[M]
[M]
S
R = alkyl, aryl
Polysulfido
Polysulfanido
Figure 1. Comparison of metal polysulfido and polysulfanido motifs.
Recently, we reported the synthesis of a zinc tetrasulfanido complex, [1]2−, via the unusual
insertion of three sulfur atoms into the Zn‒S bond of zinc dithiolate complex, [LZn]2−.21 Here, we
report the sulfur transfer reactivity of [1]2−. We demonstrate that the zinc dithiolate complex [LZn]2−
2

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can abstract sulfur from a zinc polysulfido complex, but that the resulting tetrasulfanido complex
is also in equilibrium with free elemental sulfur. We also show that [1]2− can transfer sulfur to an
electron-poor alkyne to form a zinc dithiolene complex. These reactions of [1]2− are compared to
known reactions of relevant metal polysulfido complexes to illustrate differences and similarities
between these two classes of polysulfur-containing coordination compounds.
Results
Sulfur exchange
We first compared the zinc tetrasulfanido complex [1]2– to the previously reported (N,N,N',N'-
tetramethylethylenediamine)zinc hexasulfido complex, (TMEDA)ZnS6.6 An equimolar mixture of
the dithiolate precursor [LZn]2– with (TMEDA)ZnS6 in d6-DMSO showed complete conversion to
1
the tetrasulfanido complex [1]2– within minutes by H NMR spectroscopy (Scheme 1). Although
the fate of (TMEDA)ZnS6 after sulfur transfer could not be determined by 1H NMR spectroscopy,
it is likely that insoluble ZnS is formed, as (TMEDA)ZnS6 has been shown to decompose to ZnS
upon heating.6 While it is probable that [1]2‒ also ultimately decomposes to form ZnS at elevated
temperatures, a d6-DMSO solution of [1]2‒ showed only slow conversion to other soluble zinc-
containing complexes at 80 °C (t1/2 ~ 16 d).
2–
2–
S
S
S
N
S
N
S
N
S
S
S
S
S
S
S
Zn
N
Zn
S
N
+
Zn
NMe2
d6-DMSO
N
Me2N
O
O
O
O
[1]2–
[LZn]2

(TMEDA)ZnS6
Scheme 1. Sulfur transfer from (TMEDA)ZnS6 to [LZn]2–.
Both polysulfido complexes and polysulfanido complexes are capable of transferring sulfur to
sulfur atom acceptors such as electron-rich phosphines. We have previously reported that
treatment of [1]2– with 3 equivalents of triphenylphosphine regenerates [LZn]2−, but that treatment
with fewer than 3 equivalents of phosphine forms only a mixture of [1]2– and [LZn]2– rather than
zinc polysulfanido complexes with contracted ring sizes.21 This sulfur redistribution suggests that
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[1]2– is in fast exchange with free elemental sulfur, as this behavior is similar to that of the solution
dynamics of the cyclo-S8 allotrope of elemental sulfur. Although treatment of S8 with
triphenylphosphine results in sulfur abstraction to form triphenylphosphine sulfide, S8 remains the
primary sulfur species in solution due to fast sulfur exchange.22
Figure 2 compares the negative-ion electrospray mass spectra (ESI-MS) of [1]2– and of a
mixture of [1]2– and 34S8 (3 S-atom equivalents) in CH3CN (5.0 × 10-6 M) after 2 h at room
temperature. The spectrum of the mixture displays signals at higher m/z values consistent with
statistical incorporation of 34S atoms at three different positions in the tetrasulfanido moiety of
[1]2–. This sulfur scrambling supports the proposal that [1]2– is in exchange with free elemental
sulfur and [LZn]2– in solution. However, as 34S8 and 32S8 scramble in acetonitrile on a similar
timescale (EI-MS, see ESI),23 we could not determine whether this exchange occurs one sulfur
atom at a time (Scheme 2A,B) or if three sulfur atoms are extruded simultaneously (Scheme 2C).
Figure 2. Negative-ion electrospray ionization mass spectra of [1]2– (top) and of [1]2– with
added 34S8 (3/8 equiv) in CH3CN (middle). The bottom trace shows the isotopic distribution
calculated for a statistical distribution of 32S and 34S within the tetrasulfanido moiety.
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S
S
S
2–
S
S
S
N
Zn
N
+ S
(A)
[1]2–
N
O
O
2–
S
S
S
N
S
Zn
N
– S
[1]2–
(B)
(C)
N
O
O
– 3S
[1]2–
[LZn]2–
Scheme 2. Possible pathways for sulfur exchange in [1]2–. (A) Insertion of sulfur to form a
pentasulfanido intermediate. (B) Dissociation of one sulfur atom to form a trisulfanido
intermediate. (C) Simultaneous loss of all sulfane sulfur atoms to form [LZn]2‒.
To further study sulfur exchange by [1]2−, the methoxy-substituted zinc dithiolate complex
[LOMeZn]2– was prepared (Scheme 3). The 1H NMR spectra of a mixture of [LOMeZn]2– and [1]2– in
d6-DMSO showed transfer of sulfur from [1]2– to [LOMeZn]2− to form [LZn]2– within minutes of mixing.
These data support the proposal that exchange of the tetrasulfanido complex [1]2– with elemental
sulfur and [LZn]2– is fast at room temperature, although we cannot rule out an associative
mechanism of sulfur transfer from [1]2– to [LOMeZn]2– in this reaction.
2–
+
2–
S
S
S
N
S
N
S
N
S
S
Zn
Zn
N
N
[1]2–
[LZn]2

+
N
O
O
O
O
OMe
OMe
2–
[LOMeZn]2

[1OMe
]
Scheme 3. Sulfur exchange between [1]2− and methoxy-substituted zinc dithiolate
complex [LOMeZn]2−.
Alkylation and sulfur transfer to electrophiles
We next studied reactions of [1]2– with electrophiles to compare the nucleophilicity of the
tetrasulfanido moiety to that of previously studied metal polysulfido complexes and of the parent
thiolate complex. Whereas treatment of metal polysulfides with alkyl halides typically results in
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sulfur alkylation to form alkyl polysulfanes,24 treatment of [1]2– with methyl iodide resulted in
methylation only at the ligand thiolate sulfur sites, rather than at the tetrasulfanido sulfur atoms,
to form the previously reported methylated complexes [(LMeZn)2]2– and LMe2Zn (Scheme 4, see
ESI).21 This result may suggest that the tetrasulfanido moiety of [1]2− is less nucleophilic than the
thiolate functional group, resulting in selective thiolate methylation followed by loss of elemental
sulfur. However, it is possible that selective thiolate methylation can occur, as governed by the
Curtin-Hammett principle, if the zinc dithiolate complex [LZn]2− is more reactive toward methyl
iodide than [1]2−.25,26
2-
S
S
Zn
Me
Me
N
N
2–
O
S
S
S
S
O
N
S
N
S
S
Zn
N
Zn
N
MeI (2 equiv)
MeI (1 equiv)
N
N
0.5
N
Zn
N
O
N
N
-Et4NI
-3/8 S8
-2 Et4NI
-3/8 S8
O
O
O
O
O
SMe
MeS
[(LMeZn)2]2–
[1]2–
LMe2Zn
Scheme 4. Treatment of [1]2– with one and two equivalents of methyl iodide to yield
thioether complexes.
We next studied the reaction of [1]2− with dimethyl acetylenedicarboxylate (DMAD). Addition
of DMAD (1.1 equiv) to a yellow d6-DMSO solution of [Et4N]2[1] at room temperature immediately
1
formed a red solution (Scheme 5). This new species, A, displays 11 aromatic H NMR signals,
indicating that the two ligand arms are inequivalent. Compound A converts over several hours at
1
room temperature in solution to form a mixture of two species, [2]2– and [3]2−. The H NMR
spectrum of complex [2]2– shows 6 aromatic signals, indicating that the two ligand arms are
1
symmetric. The H NMR spectrum of [2]2– does not display any signals between 3‒4 ppm,
suggesting that no DMAD-derived product is associated with the complex. Instead, a singlet at
3.49 ppm in d6-DMSO is observed for [3]2– that is not associated with any aromatic ligand-derived
signals, leading to the assignment of [3]2– as a zinc bis(dithiolene) complex. This assignment was
6

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supported by observation of a signal at 476.8620 m/z by ESI-MS. Small amounts (ca. 7%) of
1
previously-reported complexes associated with oxidation of [1]2– were also observed in the H
NMR spectrum.21
Complexes [2]2– and [3]2− were isolated from DMSO by adding diethyl ether to the dark red
reaction mixture until a red oil separated from solution. The red zinc bis(dithiolene) complex [3]2–
was separated from this mixture by extraction with acetone, leaving behind complex [2]2– as a
yellow solid. Figure 3 shows the solid-state structure of [Et4N]2[2] characterized by single crystal
X-ray diffraction (XRD) of crystals grown from vapor diffusion of diethyl ether into a CH3CN
solution of [2]2–. Complex [2]2– is a chiral D2-symmetric pseudo-octahedral zinc complex
coordinated by two pyridine(dicarboxamide) ligand frameworks connected by trisulfide linkages,
with average S‒S bond distances of 2.0520(10) Å. The Zn‒N2 and Zn‒N5 distances between the
zinc center and pyridine nitrogen atoms of [2]2− are 2.064(2) and 2.066(2) Å, respectively,
consistent with first-row M2+ metal-ligand distances reported for metal atoms bound to pyridine.27
The bond distances between zinc and the amide nitrogen atoms of the ligand framework are
longer (ca. 2.225(2) Å) than the bond distances between zinc and the pyridine nitrogen atoms,
likely due to the high coordination number at zinc. The bond angles around the zinc center are
distorted from octahedral symmetry due to ligand strain, resulting in N1‒Zn‒N3 and N4‒Zn‒N6
angles of 149.80(8)°.
The formation of [2]2− from A can be considered a zinc-templated formation of a macrocyclic
ligand framework containing two trisulfide bridges. This structure is related to that of a previously
reported bimetallic trisulfide complex that is formed upon oxidation of [1]2‒.21 The formation of
such a polysulfanide-containing macrocyclic framework by this route is somewhat unusual, as
previous examples of macrocylic polysulfanide ligands have been prepared only by addition of
S2Cl2 or other related sulfur sources to the parent dithiol ligand.28 However, treatment of the free
ligand precursor H4L with SCl2 formed a trisulfide bridge between the two thiol moieties of a single
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molecule of the bis(carboxamide)pyridine ligand precursor rather than between two molecules of
H4L (See ESI).
Figure 4 shows the solid-state structure of [Et4N]2[3] characterized by XRD of crystals grown
from vapor diffusion of diethyl ether into an acetone solution of [3]2–, confirming the assignment
as a dianionic pseudo-tetrahedral zinc bis(dithiolene) complex. The structure of [3]2– is consistent
with previously reported structures of homoleptic zinc bis(dithiolene) complexes like
bis(maleonitriledithiolato)zincate(II).29 The long C‒S bond distances of the dithiolene ligand
(1.737(11)‒1.7574(11) Å) are consistent with the fully reduced dithiolate form, as expected for the
redox-inactive Zn2+ ion. The two dithiolene ligands coordinate to Zn2+ with near-tetrahedral
geometry (휏 = 0.68).30 The shortest Zn‒S bond of [3]2– is 2.3098(4) Å and the longest is 2.3614(4)
Å. In solution, complex [3]2– is dark red, with strongly absorbing bands at 364, 488, and 508 nm.
The transition at 364 nm is assigned as a MLCT band based on studies of previously-
characterized metal dithiolene complexes.31,32 We have not yet assigned the lower-energy
transitions; although similarly intense low-energy bands have been observed in bis(dithiolene)
donor-acceptor complexes33 or assigned to interligand charge transfer,34 complex [3]2‒ should not
have similarly available acceptor orbitals.
2–
O
N
2–
O
S
S
S
N
S
N
S
S
2–
S
DMAD
S
CO2Me
CO2Me
Zn
N
Zn
N
N
S
S
S
S
A
0.5
S
+
0.5
MeO2C
MeO2C
N
S
S
CH3CN
Zn
N
N
O
O
O
O
[1]2–
[2]2–
[3]2–
Scheme 5. Reaction of [1]2− with DMAD.
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Figure 3. Solid-state structure of [2]2– as 50% thermal ellipsoids. Hydrogen atoms, solvent
molecules, and tetraethylammonium counterions have been removed for clarity.
Figure 4. Solid-state structure of [3]2– as 50% thermal ellipsoids. Hydrogen atoms and
tetraethylammonium counterions removed for clarity.
This zinc bis(dithiolene) formation from tetrasulfanido complex [1]2– has so far only been
observed for the very electron-poor DMAD substrate. A solution of [1]2– and diphenylacetylene in
d6-DMSO at room temperature showed no conversion. Treatment of [1]2− with methyl propiolate
formed a mixture of as-yet-unidentified species, possibly due to the formation of multiple
regioisomers. Altogether, these results suggest that the sulfur transfer reactivity of polysulfanido
complexes to electrophiles resembles that of previously studied polysulfido complexes.6,14,35-37
Despite the slow conversion of intermediate A to complexes [2]2− and [3]2−, we have not yet
1
been able to grow X-ray quality crystals of A for structural characterization by XRD. H NMR
spectra collected of a d6-DMSO solution of [1]2− and DMAD (1.1 equiv) showed that the aromatic
peaks assigned to A decay on the same timescale as an upfield signal at 3.79 ppm arising from
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the protons of a DMAD-derived methoxy group. Integration of the aromatic proton signals of A
and the upfield signal at 3.79 ppm suggest that A is a species with an associated equivalent of
DMAD.
We tested the hypothesis that the intermediate A may be a vinylzinc species formed by
insertion of DMAD into the Zn‒S(tetrasulfanido) bond, as previously observed for the titanium
polysulfido complex 1,4-[C5H4CH3)2Ti]2S4.38 Attempts to trap a putative vinylzinc intermediate with
methyl iodide or protonation with water did not result in products that could be identified as
resulting from such an intermediate by 1H NMR spectroscopy (See ESI). As a result, although we
cannot rule out that the initial reaction of [1]2− with DMAD forms a vinylzinc intermediate, A is more
likely a rearranged isomer of the initial DMAD insertion.
We next studied the rates of conversion of A to complexes [2]2− and [3]2−. Figure 5 shows
the electronic absorption spectra of a mixture of [1]2− and DMAD (1.1 equiv) in CH3CN over 24
hours at room temperature. The first spectral time point, recorded 30 seconds after combining
DMAD and [1]2–, showed complete consumption of [1]2–. A band at lower energy grows in over
several hours due to the formation of [3]2–. Spectral fitting of these data showed that the decay of
A and formation of [2]2− and [3]2− are consistent with a rate law that is second-order in A (see
ESI). Taken together, we propose that complex A is a monometallic species formed upon
insertion of DMAD into the Zn‒S(tetrasulfanido) bond followed by fast rearrangement of the
resulting vinylzinc species. This formation of A is then followed by a slow bimolecular step that
results in ligand exchange to form the homoleptic complexes [2]2‒ and [3]2‒.
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Figure 5. Electronic absorption spectra sampled over time after addition of DMAD (1 equiv) to
[1]2– in CH3CN (2.5 x 10-4 M). The black trace is the spectrum of [1]2–, the blue trace is the first
spectrum collected 30 s after DMAD addition, and the red trace is the final spectrum collected
24 h after DMAD addition.
Discussion
The reactions of [1]2− described above show that the sulfur exchange and redistribution
behavior of the tetrasulfanido moiety is similar to that of some examples of previously
characterized ligand-coordinated metal polysulfido complexes. Rauchfuss and co-workers have
demonstrated that removal of one sulfur atom from (TMEDA)ZnS6 in THF solution does not form
the desulfurized product (TMEDA)ZnS5, but rather a mixture of (TMEDA)ZnS6 and ZnS.6 In
acetonitrile, however, the polysulfido complexes (TMEDA)ZnS5 and (TMEDA)ZnS4 have been
observed in solution.11 Similarly, a mixture of S8 and the tetrasulfido complex (PMDETA)ZnS4
(PMDETA = N,N,N',N',N''-pentamethyldiethylenetramine) is in equilibrium with (PMDETA)ZnS5.
We note, however, that not all metal polysulfido complexes undergo this dynamic sulfur
redistribution process; in some cases, sulfur abstraction or addition results in the formation of
kinetically stable, isolable, polysulfido complexes with different ring sizes.38
Although the sulfur exchange dynamics are similar between the zinc tetrasulfanido and amine-
coordinated zinc polysulfido complexes, the primary difference between these two classes of
compounds is the reversibility of sulfur addition and removal. For both (TMEDA)ZnS6 and
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(PMDETA)ZnS4, removal of sulfur atoms via the addition of excess phosphines results in the
decomposition of the complexes and dissociation of the amine ligands to form ZnS. In the case
of [1]2−, however, sulfur abstraction is completely reversible, as the only product is the dithiolate
complex [LZn]2−. As such, it may be possible to use polysulfanido complexes as catalytic sulfur
transfer agents using elemental sulfur as the sulfur source.
The reactions of [1]2− with electrophiles suggest that the tetrasulfanido moiety may be less
nucleophilic than the metal thiolate functional group, but these results remain inconclusive. The
selectivity of methylation at the thiolate sulfur atoms supports the proposal that the zinc thiolate
moiety is more reactive, but we cannot rule out the possibility of methylation at the tetrasulfanido
group to form a methyl aryl tetrasulfide species followed by elimination of elemental sulfur.
Additionally, while the analogous addition of dichloromethane to [LZn]2− results in
chloromethylation of a thiolate sulfur (ESI-MS), addition of dichloromethane to [1]2− forms an
intractable mixture of products. This divergent behavior suggests that the alkylation of the
tetrasulfanido group is more complicated and electrophile-dependent.
The above reactions also show that complex [1]2− displays comparable nucleophilicity to that
of the polysulfido complex (PMDETA)ZnS4 and to the binary metal sulfides [M(Sx)2]2+ (M = Zn, Cd,
Ni),39 and greater nucleophilicity than the lower-coordinate (TMEDA)ZnS6. As discussed above,
the conversion of [1]2− to the putative DMAD insertion product A is complete within seconds at
room temperature, similar to the reaction between (PMDETA)ZnS4 and DMAD.11 In contrast, the
formation of (TMEDA)ZnS2C2(CO2Me)2 by addition of DMAD to (TMEDA)ZnS6 requires several
hours to reach completion.6
Conclusions
From a purely compositional and structural perspective, a metal polysulfanido complex might
be expected to exhibit properties related to both metal thiolate and metal polysulfido complexes.
The experiments discussed above support this assumption. We have shown that the zinc
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tetrasulfanido complex [1]2− undergoes reactions similar to amine-coordinated zinc polysulfido
complexes, including sulfur exchange and sulfur transfer to the electron-poor alkyne dimethyl
acetylenedicarboxylate. Current studies are underway to elucidate additional factors governing
polysulfanido reactivity; we anticipate that, as with metal polysulfido complexes, modification of
the ancillary ligand framework will permit isolation of new polysulfanido complexes with distinctive
sulfur dynamics or nucleophilicity.
†Electronic supplementary information (ESI) available. Synthetic procedures, compound
characterization, crystallographic data. CCDC 1996091 and 1996092.
Conflicts of Interest
There are no conflicts to declare.
Acknowledgments
This work was funded by the University of Notre Dame. We thank Dr. Allen Oliver for assistance
with crystallography, and Dr. William Boggess and Dr. Mijoon Lee for assistance with mass
spectrometry.
Notes and References
1. M. Draganjac and T. B. Rauchfuss, Angew. Chem., Int. Ed. Engl., 1985, 24, 742-757.
2. T. B. Rauchfuss, Inorg. Chem., 2004, 43, 14-26.
3. D. Coucouvanis, D. Swenson, P. Stremple and N. C. Baenziger, J. Am. Chem. Soc., 1979,
101, 3392-3394.
4. M. Schmidt, B. Block, H. D. Block, H. Köpf and E. Wilhelm, Angew. Chem., Int. Ed. Engl.,
1968, 7, 632-633.
5. C. Burschka, Z. Naturforsch., B: Chem. Sci., 1980, 35, 1511-1513.
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DOI: 10.1039/D0DT01384F
6. A. K. Verma, T. B. Rauchfuss and S. R. Wilson, Inorg. Chem., 1995, 34, 3072-3078.
7. A. Müller, E. Krickemeyer, H. Bögge, W. Clegg and G. M. Sheldrick, Angew. Chem., Int. Ed.
Engl., 1983, 22, 1006-1007.
8. C. M. Bolinger, T. B. Rauchfuss and A. L. Rheingold, Organometallics, 1982, 1, 1551-1553.
9. D. M. Giolando and T. B. Rauchfuss, Organometallics, 1984, 3, 487-489.
10. H. Köpf, S. K. S. Hazari and M. Leitner, Z. Naturforsch., B: Chem. Sci., 1978, 33, 1398-
1404.
11. R. J. Pafford and T. B. Rauchfuss, Inorg. Chem., 1998, 37, 1974-1980.
12. R. Steudel and E. Strauss, Angew. Chem., Int. Ed. Engl., 1984, 23, 362-363.
13. C. M. Bolinger, T. B. Rauchfuss and S. R. Wilson, J. Am. Chem. Soc., 1981, 103, 5620-
5621.
14. C. M. Bolinger and T. B. Rauchfuss, Inorg. Chem., 1982, 21, 3947-3954.
15. R. J. Pafford, J. Chou and T. B. Rauchfuss, Inorg. Chem., 1999, 38, 3779-3786.
16. D. M. Giolando, T. B. Rauchfuss and S. R. Wilson, J. Am. Chem. Soc., 1984, 106, 6455-
6456.
17. A. Shaver, J. M. McCall, P. H. Bird and N. Ansari, Organometallics, 1983, 2, 1894-1896.
18. A. Shaver and P. Plouffe, Inorg. Chem., 1994, 33, 4327-4333.
19. N. Lau and M. D. Pluth, Curr. Opin. Chem. Biol., 2019, 49, 1-8.
20. S. Dev, E. Ramli, T. B. Rauchfuss and C. L. Stern, J. Am. Chem. Soc., 1990, 112, 6385-
6386.
21. M. Ballesteros and E. Y. Tsui, Inorg. Chem., 2019, 58, 10501-10507.
22. J. P. Donahue, Chem. Rev., 2006, 106, 4747-4783.
23. F. N. Tebbe, E. Wasserman, W. G. Peet, A. Vatvars and A. C. Hayman, J. Am. Chem. Soc.,
1982, 104, 4971-4972.
24. R. Steudel, S. Förster and J. Albertsen, Chem. Ber., 1991, 124, 2357-2359.
25. P. I. Pollak and D. V. Curtin, J. Am. Chem. Soc., 1950, 72, 961-965.
26. V. Bogdándi, T. Ida, T. R. Sutton, C. Bianco, T. Ditrói, G. Koster, H. A. Henthorn, M.
Minnion, J. P. Toscano, A. Vliet, M. D. Pluth, M. Feelisch, J. M. Fukuto, T. Akaike and P. Nagy,
Br. J. Pharmacol., 2019, 176, 646-670.
14

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Dalton Transactions
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DOI: 10.1039/D0DT01384F
27. R. F. See, R. A. Kruse and W. M. Strub, Inorg. Chem., 1998, 37, 5369-5375.
28. N. B. Egen and R. A. Krause, J. Inorg. Nucl. Chem., 1969, 31, 127-135.
29. J. Stach, R. Kirmse, J. Sieler, U. Abram, W. Dietzsch, R. Boettcher, L. K. Hansen, H.
Vergoossen and M. C. M. Gribnau, Inorg. Chem., 1986, 25, 1369-1373.
30. L. Yang, D. R. Powell and R. P. Houser, Dalton Trans., 2007, 955-964.
31. S. Liu, P. Wu, Y. Li and D. Zhu, Phosphorus, Sulfur, Silicon, Relat. Elem., 1994, 90, 219-
227.
32. H. Müller, A. P. Molina, B. Z. Narymbetov, L. V. Zorina, S. S. Khasanov and R. P. Shibaeva,
Z. Anorg. Allg. Chem., 1998, 624, 1492-1496.
33. J. Burgess, K. M. C. Davis, R. D. W. Kemmitt, J. B. Raynor and J. Stocks, Inorg. Chim. Acta,
1970, 4, 129-132.
34. S. C. Ratvasky, B. Mogesa, M. J. van Stipdonk and P. Basu, Polyhedron, 2016, 114, 370-
377.
35. C. M. Bolinger, J. E. Hoots and T. B. Rauchfuss, Organometallics, 1982, 1, 223-225.
36. T. R. Halbert, W. H. Pan and E. I. Stiefel, J. Am. Chem. Soc., 1983, 105, 5476-5477.
37. M. Draganjac and D. Coucouvanis, J. Am. Chem. Soc., 1983, 105, 139-140.
38. D. M. Giolando, T. B. Rauchfuss, A. L. Rheingold and S. R. Wilson, Organometallics, 1987,
6, 667-675.
39. D. Coucouvanis, P. R. Patil, M. G. Kanatzidis, B. Detering and N. C. Baenziger, Inorg.
Chem., 1985, 24, 24-31.
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The sulfur transfer reactions of a zinc tetrasulfanido complex are explored and contrasted with
those of metal polysulfidos.