Syntheses of Mixed-Metal Sulfide Cubane-Type Clusters with the Novel PdMo3S4 Core and Reactivities of the Unique Tetrahedral Pd Site Surrounded by Sulfide Ligands toward Alkenes, CO, tBuNC, and Alkynes

Unprecedented Solvent‐Assisted Reactivity of Hydrido W3CuS4 Cubane Clusters: The Non‐Innocent Behaviour of the Cluster‐Core Unit

“…The next step in this mechanism involves release of the hydrated chloride, which occurs with an energy barrier of 2.4 kcal mol À1 to yield the ion pair-like species [6] À species, as expected for a step involving separation of two species of different charge, hence the dissociation of chloride from [5···H 2 O] + can be described as occurring in two steps: decoordination of chloride from the copper atom coupled with sulfur recoordination, with the hydrated chloride still close by, and dissociation of the resulting ion-pair-like species. The acetonitrile molecule enters the copper coordination sphere in the next step, which results in decoordination of a sulfur atom and gives rise to the new open-cluster species [7] 2 + , which finally loses the water molecule attached to the Cu atom to yield the reaction products. The open-core species [5···H 2 …”

“…The second open-core cluster species appearing in Figure 11 corresponds to [7] 2 + . In this case, there is also a stabilizing hydrogenbonding interaction between one hydrogen of the H 2 O ligand and the dissociated sulfur atom (2.481 ).…”

“…+ with the ion-pair-like structure (max4), and [7] 2 + with [2] 2 + (max5). The geometries of max3, max4 and max5 are in agreement with each ligand substitution step, as shown in Figure 12.…”

“…Furthermore, the smoothness of the energy profile, the accessibility of the energy barriers under normal reaction conditions, and the fact that the overall process is not too energy-demanding ensure that this mechanism is possible under the experimental reaction conditions. The highest energy point in Figure 11 corresponds to max5, that is, to the barrier for dissociation of water from [7] 2 + in a step that follows chloride dissociation. Thus, the processes in Equations (19)- (22) could occur as rapid pre-equilibria leading to small amounts of [5] 2 + , [6] 2 + and [7] 2 + ; the ratedetermining step would be the process in Equation (22).…”

“…Nevertheless, catalytic reactions and mechanistic studies have been largely unexplored. [13] Exceptions to the latter are palladium-and nickel-based Mo 3 M'S 4 systems where the molybdenum atoms are coordinated to 1,4,7-triazacyclononane, h 5 -pentamethylcyclopentadienido or aquo ligands, which catalyse a variety of processes including the addition of methanol or carboxylic acids to electron-deficient alkynes, [7] the intramolecular hydroamination of aminoalkynes, [14] the cyclisation of alkynoic acids to enol lactones [15] and the hydrodesulfurisation of benzothiophene. [16,17] Catalytic studies centred on Mo 3 RuS 4 clusters have explored their behaviour as effective catalysts for N À N bond cleavage in hydrazines.…”