Prototype Supported Metal Cluster Catalysts: Ir₄ and Ir₆

Abstract

Conversion of adsorbed mononuclear metal complexes, usually organometallics, into supported clusters by treatment in reactive atmospheres * Adsorption of metal clusters stabilized with organic ligands * Deposition of size-selected ligand-free gas-phase metal clusters onto planar supports.

Structures, relative energies, and ligand dissociation energies of iridium carbonyl phosphine clusters

“…Iridium complexes play important roles in oxidation (e.g., of alcohols [4][5][6], phenols [7][8][9], and amines [10,11]), hydrogenation [12,13], C-H activation [14][15][16], cycloaddition (e.g., [2 + 2 + 2] [17][18][19], [2 + 2 + 1] [20,21], and [4 + 2] [22,23]), cycloisomerization [1,2], and ring-opening reactions [24]. The richness of this chemistry explains the broad interest in the properties of the family of iridium complexes and clusters [25]. Ozin and coworkers [26][27][28] reported the synthesis of Ir(CO) n (n = 1-4) and Ir 2 (CO) 8 clusters in a matrix.…”

The role of Ir4 cluster in enhancing the adsorption of CO2 on selected zeolites – GCMC simulations

“…Gates [20][21][22]. Their studies [23] bring insight into a catalytic activity of supported metal clusters and it was revealed that metal clusters bonded to oxide or zeolite supports, may combine advantages of solid catalysts with the selectivity of soluble molecular catalysts.…”

Beyond Relationships Between Homogeneous and Heterogeneous Catalysis

“…The ideas summarized here go beyond single-metal-atom complex catalysts; the next level of complexity is small, uniform clusters of metal atoms [20]. Although the complexity is greater, the catalyst characterization in some ways becomes more informative than for single-atom metal complexes.…”

“…Ligands placed on neighboring metal centers in MgO-supported rhodium dimer catalysts tune the catalytic activity and selectivity for hydrogenation of 1,3-butadiene [23,24]. Work with Ir 4 and Ir 6 clusters on a zeolite included determination of the energetics of hydrogen addition as well as hydrogen spillover from the support [20].…”

“…Although the complexity is greater, the catalyst characterization in some ways becomes more informative than for single-atom metal complexes. For example, structures of clusters incorporating several heavy metal atoms on crystalline supports have been determined by STEM complemented by EXAFS spectroscopy, illustrated by Ir 6 [20], Os 3 , Os 5 , and Os 10 [21].…”