Push–Pull Molybdenum Trisdithiolenes Allow Rapid Nonconventional Binding of Ethylene at Ligand Sulfur Atoms

Abstract

Adding to the mix: Mixed dithiolene complexes of molybdenum, such as [Mo{S2C2(CF3)2}2{S2(C6H4)}], bind ethylene rapidly, in a nonconventional fashion, at the sulfur atoms (see scheme). In the presence of additional donor ligands, substitution of the metal‐bound 2,3‐dihydro‐1,4‐dithiin occurs, providing a new approach to mixed‐ligand molybdenum bis‐ and trisdithiolenes.

Molybdenum Dithiolene Complexes as Structural Models for the Active Sites of Molybdenum(IV) Sulfide Hydrodesulfurization Catalysts

“…Using density functional theory (DFT), we found that both a pseudo-tetrahedral structure and the pyramidal structure that is relevant here are minima on the hypersurface for Mo(tfd) 2 , as confirmed by geometry optimization and subsequent frequency analysis (no imaginary frequency). The pyramidal structure (uphill relative to the pseudo-tetrahedral structure by 12.3 kcal/ mol) has two low-lying empty orbitals (LUMO and NLUMO), shown in Figure 4, that contain some p-orbital contribution from the sulfur atoms but are largely metalbased and correspond roughly to d x [24] [Mo(tfd) 2 …”

“…The most similar one is the ethylene adduct [Mo(tfd) 2 -{bdt(CH 2 CH 2 )}], with an average distance of 2.523 Å to the sulfur atoms on the dihydrobenzodithiin ligand. [24] The closest non-dithiolene-based Mo IV system is an octahedral molybdenum "S 4 -crown" thioether complex, with slightly shorter Mo-S(thioether) distances (2.469-2.498 Å). [28] Computed Mo-S distances for dht and tht bound to a Mo 3 S 9 catalyst model fragment are 2.53 Å and 2.50 Å, respectively.…”

“…[24] Grubbs' second generation catalyst, tetrahydrothiophene (tht) (99 %) and bis-(trimethylsilyl)acetylene (btmsa) (99 %) were obtained from Sigma Aldrich. Tetrahydrothiophene was redistilled and dried with molecular sieves (3 Å) before use.…”

“…intraligand alkene addition) to form a metal-chelating dihydrobenzodithiin moiety. [24] The weakly bound dihydrobenzodithiin can be substituted with a variety of nucleophiles, which allows access to new molybdenum bis-and trisdithiolene complexes. In this paper we extend this versatile method to create molybdenum bisdithiolenes with thioether ligands (partially hydrogenated thiophenes), which provide structural models for postulated intermediates in MoS 2 -based HDS catalysis.…”

Diverse reactivities of aromaticity–unsaturation coexisted metalladithiolene rings

“…[Mo(tfd) 3 ] or [Mo(bdt) 3 ] reacted with ethylene gave the corresponding 2,3-dihydro-1,4-dithiin derivative through a transient intraligand S,S 0 -cycloadduct. However, the mixed ligand tris(dithiolene) complex, [Mo(bdt)(tfd) 2 ] (4) or [Mo(bdt) 2 (tfd)], was reacted with ethylene and then the intraligand S,S 0 -cycloadduct (5) was successfully isolated (Chart 7(a)) [36]. This reaction is also explained by a molecular orbital overlap between dithiolene LUMO and alkene HOMO.…”