The reactivity of [MoS4]2- (1) toward PMe3 was explored in the presence and absence of proton donors. Whereas MeCN solutions of (Et4N)2[MOS4] and PMe3 are stable, in the presence of H2S such solutions catalyze formation of H2 and SPMe3. Addition of NH4+ to such solutions afforded MoS2(PMe3)4 (2), which can be prepared directly from (NH4)2. Compound 2 is reactive toward thiols via a process proposed to involve the initial dissociation of one PMe3 ligand, a hypothesis supported by the relative inertness of trans-MoS2(dmpe)2. Benzene solutions of 2 react with EtSH to give Mo2(μ-S)(μ-SH)(PMe3)4(SEt)3 (3Et). Analogous reactions with thiocresol (MeC6H4SH) and H2S gave Mo2(μ-S)(μ-SH)(PMe3)4(SR)3 (R = tol, H). Crystallographic analyses of 3Et, 3H, and 3tol indicate dinuclear species with seven terminal ligands and a Mo2(μ-SR)(μ-S) core (rMo-Mo = 2.748(1) Å). From reaction mixtures leading to 3Et from 2, we obtained the intermediate Mo2IV(μ-S)2(SEt)4 (PMe3)2 (4), an edge-shared bis(trigonal pyramidal) structure. Compounds 3H and 3Et react further with H2S to give Mo4(μ2-S)4(μ3-S) 2(PMe3)6(SH)2 (5H) and Mo4(μ2-S)4(μ3-S) 2(PMe3)6(SEt)2 (5Et), respectively. Analogously, W4(μ2-S)4(μ3-S) 2(PMe3)6(SH)2 was synthesized from a methanol solution of (NH4)2WS4 with H2S and PMe3. A highly accurate crystallographic analysis of (NH4)2MoS4 (R1 = 0.0193) indicates several weak NH···S interactions.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry