Aggregation of PMe₃-Stabilized Molybdenum Sulfides and the Catalytic Dehydrogenation of H₂S

Abstract

The reactivity of [MoS(4)](2-) (1) toward PMe(3) was explored in the presence and absence of proton donors. Whereas MeCN solutions of (Et(4)N)(2)[MoS(4)] and PMe(3) are stable, in the presence of H(2)S such solutions catalyze formation of H(2) and SPMe(3). Addition of NH(4+) to such solutions afforded MoS(2)(PMe(3))(4) (2), which can be prepared directly from (NH(4))(2)[1]. Compound 2 is reactive toward thiols via a process proposed to involve the initial dissociation of one PMe(3) ligand, a hypothesis supported by the relative inertness of trans-MoS(2)(dmpe)(2). Benzene solutions of 2 react with EtSH to give Mo(2)(mu-S)(mu-SH)(PMe(3))(4)(SEt)(3) (3Et). Analogous reactions with thiocresol (MeC(6)H(4)SH) and H(2)S gave Mo(2)(mu-S)(mu-SH)(PMe(3))(4)(SR)(3) (R = tol, H). Crystallographic analyses of 3Et, 3H, and 3tol indicate dinuclear species with seven terminal ligands and a Mo(2)(mu-SR)(mu-S) core (r(Mo)(-)(Mo) = 2.748(1) A). From reaction mixtures leading to 3Et from 2, we obtained the intermediate Mo(IV)(2)(mu-S)(2)(SEt)(4)(PMe(3))(2) (4), an edge-shared bis(trigonal pyramidal) structure. Compounds 3H and 3Et react further with H(2)S to give Mo(4)(mu(2)-S)(4)(mu(3)-S)(2)(PMe(3))(6)(SH)(2) (5H) and Mo(4)(mu(2)-S)(4)(mu(3)-S)(2)(PMe(3))(6)(SEt)(2) (5Et), respectively. Analogously, W(4)(mu(2)-S)(4)(mu(3)-S)(2)(PMe(3))(6)(SH)(2) was synthesized from a methanol solution of (NH(4))(2)WS(4) with H(2)S and PMe(3). A highly accurate crystallographic analysis of (NH(4))(2)MoS(4) (R(1) = 0.0193) indicates several weak NH.S interactions.

Diammonium tetrathiotungstate(VI), (NH4)2[WS4], at 150 K

“…2). No disordering of the H atoms in the NH 4 + ion is found in (I), unlike in the corresponding Mo analogue, where the H atoms are disordered over two orientations of both NH 4 + cations (Schwarz et al, 2003). Several short NÐHÁ Á ÁS contacts, with HÁ Á ÁS ranging from 2.57 to 3.03 A Ê , are observed between the cations and the anions, which are comparable with those of 2.55±3.02 A Ê reported for the Mo analogue ( Table 2).…”

“…In recent work, it has been shown that the (NH 4 ) + ion signi®cantly in¯uences the chemical behaviour of [MoS 4 ] 2À ; this has been attributed to hydrogen-bonding interactions between the cations and anions in (NH 4 ) 2 [MoS 4 ] (Schwarz et al, 2003). In view of our recent interest in the chemistry of tetrathiotungstates (Srinivasan et al, 2003), we have redetermined the structure of diammonium tetrathiotungstate at low temperature.…”

Solution Processing of Chalcogenide Semiconductors via Dimensional Reduction

“…[98] In (NH 4 ) 2 MoS 4 , the extended framework of MoS 2 is broken up into discrete MoS 4 2À moieties separated by NH 4 þ cations. [99] However, high-temperature post-deposition anneals are generally required to achieve crystalline films (600-800 8C), rendering the process incompatible with organicbased flexible substrate materials or soda lime glass. A similar approach with (CH 3 NH 3 ) 2 MS 4 (M ¼ W, Mo) dissolved in organic solvents and using an inert atmosphere anneal led to highly conducting and textured n-type MoS 2 (%50 V À1 cm À1 ) and WS 2 (%7 V À1 cm À1 ) films.…”

Synthesis, X‐ray Structures, Spectroscopic and Thermal Characterization of Two New Organic Ammonium Tetrathiotungstates

“…It has also been reported in the literature for Mo-S compounds that the chemical properties of [MoS 4 ] 2Ϫ can be substantially changed by surrounding it with bulky organic ammonium cations [20]. The role of hydrogen bonding interactions between the cation and anion to influence the reactivity characteristics has also been reported [21]. In view of this we are investigating the synthesis, structural and thermal characterization of organic ammonium tetrathiometalates of the group VI metals and have already shown that a rich chemistry of tetrathiomolybdates can be developed by suitably changing the hydrogen bonding interactions between the cation and [MoS 4 ] 2- [22].…”