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Formate dehydrogenase (FDH) enzymes catalyze redox interconversion of CO
2
and HCO
2
-
, with a key mechanistic step being the transfer of H
-
from HCO
2
-
to an oxidized active site featuring a [M
VI
≡S] group in a sulfur-rich environment (M = Mo or W). Here, we report reactivity studies with HCO
2
-
and other reducing agents of a synthetic [W
VI
≡S] model complex ligated by dithiocarbamate (dtc) ligands. Reactions of [W
VI
S(dtc)
3
][BF
4
] (
1
) conducted in MeOH solvent generated [W
VI
S(S
2
)(dtc)
2
] (
2
) and [W
V
S(μ-S)(dtc)]
2
(
3
) products by a solvolysis pathway that was accelerated by the presence of [Me
4
N][HCO
2
] but did not require it. Under MeOH-free conditions, the reaction of
1
with [Et
4
N][HCO
2
] produced some [W
IV
(μ-S)(μ-dtc)(dtc)]
2
(
4
), but predominantly [W
V
(dtc)
4
]
+
(
5
), along with stoichiometric CO
2
detected by headspace GC analysis. Stronger hydride sources such as K-Selectride generated the more reduced analog,
4
, exclusively. Reaction of
1
with the electron donor, CoCp
2
, also produced
4
and
5
in varying amounts depending on reaction conditions. These results indicate that formates and borohydrides act as electron donors rather than hydride donors towards
1
, an outcome that diverges from the behavior of FDHs. The difference is ascribed to the more oxidizing potential of [W
VI
≡S] complex
1
when supported by monoanionic dtc ligands that allows electron transfer to outcompete hydride transfer, as compared to the more reduced [M
VI
≡S] active sites supported by dianionic pyranopterindithiolate ligands in FDHs.