Efficient (Z)-selective semihydrogenation of alkynes catalyzed by air-stable imidazolyl amino molybdenum cluster sulfides

Abstract

Imidazolyl amino cuboidal Mo3(µ3-S)(µ-S)3 clusters have been investigated as catalysts for the semihydrogenation of alkynes. For that purpose, three new air-stable cluster salts [Mo3S4Cl3(ImNH2)3]BF4 ([1]BF4), [Mo3S4Cl3(ImNH(CH3))3]BF4 ([2]BF4) and [Mo3S4Cl3(ImN(CH3)2)3]BF4 ([3]BF4)...

Spin-Crossing in the (Z)-Selective Alkyne Semihydrogenation Mechanism Catalyzed by Mo3S4 Clusters: A Density Functional Theory Exploration

“…It should be noted that the formation of the dithiolene adduct (pathway A) was computed to feature a relatively low free energy barrier (11.5 kcal·mol –1 , pathway A), with the step being slightly exergonic by −1.0 kcal mol –1 . This supports the experimentally observed equilibrium between the trinuclear cluster and the dithiolene adduct …”

“…This supports the experimentally observed equilibrium between the trinuclear cluster and the dithiolene adduct. 29 The dynamic character of the system plays a critical role in the mechanism since both species, the cluster and the dithiolene complex, are in solution, leading to the interconnection of the two catalytic cycles. From this situation, the formation of the hydrosulfido S−H bonds ([I], pathway B) on 1 + has the lowest computed barrier for the H 2 activation (ΔG ‡ = 19.2 kcal•mol −1 ).…”

“…While the diamino [Mo 3 S 4 Cl 3 (dmen) 3 ] + (dmen = Me 2 NCH 2 CH 2 NMe 2 ) cluster catalyzes the semihydrogenation of diphenylacetylene (dpa) to produce mixtures of ( Z )- and ( E ) -alkenes ( Z / E ca . 6/1) under harsh conditions with moderate yields, the imidazolyl amino [Mo 3 S 4 Cl 3 (ImNH 2 ) 3 ] + cluster performs the selective transformation toward the ( Z )-alkene under softer conditions with quantitative yields . Based on catalytic and stoichiometric experiments, we were able to propose a reaction mechanism for the [Mo 3 S 4 Cl 3 (dmen) 3 ] + cluster, depicted in Figure a, which starts with the formation of a dithiolene adduct by interaction between the bridging sulfides of the molybdenum cluster complex and the alkyne substrate.…”

Selective Dehydrogenation of Formic Acid Catalyzed by Air‐Stable Cuboidal PN Molybdenum Sulfide Clusters

“…For that purpose, we tested several trinuclear Mo 3 S 4 compounds, represented in Table 1. Except for 4 + , the synthesis and crystal structures of the rest of the compounds have been previously reported [25,27–30] . The catalytic tests were performed in a glass reactor connected to a manual burette (Figure SI5).…”

“…[31] Two aminophosphino trinuclear complexes (3 + and 4 + ) differing in the nature of the group attached to the phosphorous atom and three imidazolyl amino cluster compounds (5 + -7 + ) with the NH 2 moiety gradually substituted by methyl groups were investigated in our work. [29,30] Complex 1, a typical precursor for the preparation of Mo 3 S 4 complexes was also tested. [27] For comparative purposes, we have also included in our studies the diphosphino Mo 3 S 4 hydrido cluster (2 + ) and the pincer complex (PN H P)Mo(OCOH)(CO) 2 (8).…”