Facets of early transition metal–sulfur chemistry: Metal–sulfur ligand redox, induced internal electron transfer, and the reactions of metal–sulfur complexes with alkynes

Cuboidal Mo3S4 Clusters as a Platform for Exploring Catalysis: A Three-Center Sulfur Mechanism for Alkyne Semihydrogenation

“…Thus, insertion of the alkyne results in a reduction of the metal atoms from Mo(IV) 3 to Mo(III) 2 Mo(IV), as the dithiolene cluster contains eight cluster skeletal electrons for the formation of two single and one double Mo−Mo bonds. 18 The structure of [2] + is well-reproduced by DFT calculations (see below) and supports the existence of an internal electron transfer also reflected in their redox properties. Thus, whereas the cyclic voltammogram of [1] + shows a sole reversible reduction at −0.45 V (vs. Ag/AgCl), [2] + undergoes one reversible reduction at −0.34 V and two quasi-reversible oxidations at 0.84 and 1.16 V, respectively (see Figure S1 in the SI).…”

“…This implies an internal electron transfer process induced by the interaction with dmad, which is also reflected in the shortening of the Mo–Mo bond between the Mo centers not involved in the [3 + 2] cycloaddition reaction from 2.759 Å in [ 1 ] + , characteristic of a Mo–Mo single bond, to 2.653 Å in [ 2 ] + , typical of a Mo–Mo double bond. Thus, insertion of the alkyne results in a reduction of the metal atoms from Mo­(IV) 3 to Mo­(III) 2 Mo­(IV), as the dithiolene cluster contains eight cluster skeletal electrons for the formation of two single and one double Mo–Mo bonds . The structure of [ 2 ] + is well-reproduced by DFT calculations (see below) and supports the existence of an internal electron transfer also reflected in their redox properties.…”

A Bio‐Inspired Switch Based on Cobalt(II) Disulfide/Cobalt(III) Thiolate Interconversion

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Disulfide/thiolate interconversion supported by transition-metal ions is proposed to be implicated in fundamental biological processes, such as the transport of metal ions or the regulation of the production of reactive oxygen species. [2] The idea that metal ions can play an active role in the disulfide/thiolate interconversion of essential biological processes has only emerged during the last decade. The removal of Cl À from the Co III complex leads to the formation of a bis(m-thiolato) m-disulfido dicobalt(II) complex, [Co 2 II,II LSSL] 2+ (2 2+ ).

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“…[1] On the other hand, thiolates act as terminal or bridging ligands for transition-metal ions to generate self-assembled complexes of different nuclearities. [2] The idea that metal ions can play an active role in the disulfide/thiolate interconversion of essential biological processes has only emerged during the last decade. [3] However, this hypothesis has never been undoubtedly demonstrated nor completely understood.…”

Reaction Chemistry of the syn-[Mo2O2(μ-S)2(S2)(DMF)3] Complex with Cyanide and Catalytic Thiocyanate Formation

“…Molybdenum–sulfur complexes with disulfide and terminal sulfido ligands display interesting properties due to their participation in both stoichiometric − and catalytic reactions, − including episulfidation and sulfur transfer reactions. , The rich reaction chemistry encountered is rightfully credited to the accessible redox properties of both Mo and S. − Catalytic sulfur transfer reactions employing mononuclear molybdenum complexes participating in oxidative addition/reductive elimination reactions also suffer from a facile catalyst deactivation to form sulfur-bridged binuclear molybdenum complexes . Binuclear sulfur-bridged molybdenyl complexes based on the core [Mo 2 O 2 (μ-S) 2 ] 2+ with terminal disulfide ligands are therefore particularly interesting where the spin-paired Mo­(V) centers with a formal Mo–Mo bond are very stable toward oxygen and water, , and the disulfide ligand functions as a reactive site.…”