Unique reactivity characteristics of Mo-coordinated S2−2 and S2−4 ligands

Abstract

The synthesis of the new dithiolene complexes, [{(MeOOC),C,S2}2Mo(2-S)]; and [OMo(S2C2(COOMe)2)2]2-, is reported. These complexes are obtained by the reaction of dicarbomethoxyacetylene (DMA) with either [(S~)MO(S)(~~-S)~MO(S)(S~)]~-or [(CS~)MO(S)(~~-S)~MO(S)(CS~)]~-and [OMO(S~)~]~-, respectively. The reaction of [(S4)Mo(0)(~2-S)2Mo(O)(S2)]2-with DMA results in the new dithiolene complex [{(MeOOC)2C2S2}M~(0)(~2-S)]~, which is the isomeric form of the vinyl disulfide complex obtained in the reaction of the [(S2)Mo(0)(~2-S)2Mo(O)(S2)]2-complex with DMA. The difference in reactivity between the two complexes that contain the same [Mo202S212+ core is attributed to the intrinsically different reactivity characteristics of the Sg-and S:-ligands. As a result of Mo-S d,-p, bonding an alternation in the S-S bond lengths is observed in virtually all of the structurally characterized Mo-S4 units. The consequent weakening of the S-S bonds adjacent to the Mo-S bonds allows for the ready dissociation of $3 from the MO-coordinated Si-ligands. This weakening also accounts for the facile formation of dithiolenes in cycloaddition reactions of alkynes with the Mo-S, units. By comparison, the S-S bond in side-on MO-coordinated St-ligands is strengthened as a result of depopulation of the ligand x*-orbitals. Reactions of the latter with alkynes do not proceed by cycloaddition. Instead, insertion into the Mo-S bond has been reported for at least one such reaction. The importance of activated polysulfide ligands in the hydrodesulfurization reaction is discussed.

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

“…[114]. Vinyl disulfide complexes have also been observed in Ti (vide supra) [100] and Mo Cp chemistry [115].…”

Synthesis, characterization, and spectroscopy of model molybdopterin complexes

“…There is no indication of trithiolene complex formation in the aryl alkyne reactions of DIFPEPP and PEPP and therefore, at this time we do not know whether trithiolene precursors to dithiolenes are formed in every reaction of a pterinylalkyne and [TEA][Tp*Mo(S)(S 4 )]. There is precedent for the formation of trithiolenes as the initial product of alkyne reaction with Mo(4+) tetrasulfide reagents [31]. The more complicated BOPP and BMOPP pterin-dithiolene model systems are still under study.…”

Reactivity of tetrathiometalates with alkynes. Synthesis and characterisation of dithiolene complexes of Mo, W, and V by ESMS and XRD

“…Thus, a di-Mo(V) complex was isolated containing two dithiolene ligands, (NEt 4 ) 2 [-Mo 2 (X) 2 (l-S) 2 (g 2 -S 2 C 2 (CO 2 Me) 2 ) 2 ] 1, (X = O or S). As DMA reacts quite rapidly with terminal disulphide ligand, [23][24] it is not possible to evidence transient species. A general scheme is proposed in Fig.…”