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The synthesis of the previously‐reported atomically‐precise [Rh16Au6(CO)36]6− (1) nanocluster has been optimized by screening different reaction variables like solvent, stoichiometric ratio, counterion and atmosphere. Its multivalence properties have also been studied by means of electrochemical and spectroelectrochemical techniques; the results pointed out a remarkable electron‐sponge behaviour, as under such experimental conditions 1 is capable to release one electron and accept up to four more, while retaining its molecular structure. This scarce structural variation has been confirmed through DFT calculations on those species whose redox processes showed the maximum reversibility, namely [Rh16Au6(CO)36]7− and [Rh16Au6(CO)36]5−. Moreover, we report herein the isolation and characterization of the new [Rh10Au(CO)26]3− (2) nanocluster, which represents one of the major fallouts of the synthetic pathway investigation of 1. Finally, we disclosed the existence of further species that, from preliminary results, appear to be new large atomically‐precise Rh−Au nanoclusters, which will be the subject of future investigations. Cluster 2 has been identified via single‐crystal X‐ray diffraction analysis, and the characterization of both clusters 1 and 2 completed by infrared (IR) spectroscopy and Electrospray Ionization Mass Spectrometry (ESI‐MS). [ABSTRACT FROM AUTHOR]

The present microreview focuses on different typologies of isomerism documented along the years for metal carbonyl clusters (MCCs), and outlines their analogies to other classes of ligand‐protected molecular clusters and nanoclusters. Isomerism in molecular MCCs is discussed within two main categories, that is, surface isomerism and core isomerism. The first Section presents some representative examples of surface isomerism involving inorganic (carbonyls and hydrides) and organic ligands, as well as isomerism due to ML fragments decorating the cluster surface. The second Section focuses on three major categories of core isomerism, that is: (1) isomers that mainly differ on M–M distances; (2) isomers displaying different structures of the metal kernels; (3) isomers possessing almost identical metal kernels and ligand shells, but differing for the positions of different types of metal atoms within the metal kernel. The third Section briefly discusses two related and very rare cases of isomerism, that is, polymerisation and coordination isomerism. General conclusions are outlined in the final Section. [ABSTRACT FROM AUTHOR]

This work is an attempt to understand and optimize the rare earth elements leaching from Moroccan phosphogypsum using a nitric acid solution. The Plackett–Burman statistical design was used to identify the statistically significant factors responsible for the optimum leaching conditions. With this purpose, the following seven variables were studied: nitric acid concentration (X1), solid‐to‐liquid ratio (X2), temperature (X3), leaching time (X4), stirring speed (X5), drying (X6), and particle size (X7). Given that the leaching recovery of rare earth elements is limited by the quantity of dissolved phosphogypsum, we examined two simultaneous responses, namely, the leaching efficiency of rare earth elements YREEs and the leaching efficiency of calcium YCa (dissolution rate of phosphogypsum). The predicted values of the two fitted models were in good agreement with the experimental values by a coefficient of determination (R2) equal to 98.6% and 96.50%, respectively. In the model of YREEs, only the effect of drying was found to be statistically insignificant with a p‐value greater than 0.05. Nitric acid concentration, solid‐to‐liquid ratio, and temperature are the only variables having a statistically significant effect in the model of YCa. At a dissolution rate of phosphogypsum equal to 30.13%, the leaching efficiency of rare earth elements from our sample has reached a maximum of 87.55%. The optimal experimental conditions are a nitric acid concentration of 3.3 M, a solid‐to‐liquid ratio of 1/9, a temperature of 75°C, a leaching time of 20 min, a stirring speed of 200 rpm, and d ≤ 100 µm as a particle size. [ABSTRACT FROM AUTHOR]

In this paper, we present a comparative study of the redox properties of the icosahedral [Rh12E(CO)27]n− (n = 4 when E = Ge or Sn and n = 3 when E = Sb or Bi) family of clusters through in situ infrared spectroelectrochemistry experiments and density functional theory computational studies. These clusters show shared characteristics in terms of molecular structure, being all E-centered icosahedral species, and electron counting, possessing 170 valence electrons as predicted by the electron-counting rules, based on the cluster-borane analogy, for compounds with such metal geometry. However, in some cases, clusters of similar nuclearity, and beyond, may show multivalence behavior and may be stable with a different electron counting, at least on the time scale of the electrochemical analyses. The experimental results, confirmed by theoretical calculations, showed a remarkable electron-sponge behavior for [Rh12Ge(CO)27]4− (1), [Rh12Sb(CO)27]3− (3), and [Rh12Bi(CO)27]3− (4), with a cluster charge going from −2 to −6 for 1 and 3 and from −2 to −7 for cluster 4, making them examples of molecular electron reservoirs. The [Rh12Sn(CO)27]4− (2) derivative, conversely, presents a limited ability to exist in separable reduced cluster species, at least within the experimental conditions, while in the gas phase it appears to be stable both as a penta- and hexa-anion, therefore showing a similar redox activity as its congeners. As a fallout of those studies, during the preparation of [Rh12Sb(CO)27]3−, we were able to isolate a new species, namely, [Rh11Sb(CO)26]2−, which presents a Sb-centered nido-icosahedral metal structure possessing 158 cluster valence electrons, in perfect agreement with the polyhedral skeletal electron pair theory. [ABSTRACT FROM AUTHOR]

Reaction of [HRu3(CO)11]− (1) with [Ir(COD)Cl]2 in CH2Cl2 under a H2 atmosphere afforded dihydride [H2Ru3Ir(CO)12]− (2), which was quantitatively protonated to H3Ru3Ir(CO)12 (3) by strong acids such as HBF4·Et2O. The related mono-hydride [HRu3Ir(CO)12]2− (4) was obtained by deprotonation of 2 with a strong base such as KOtBu, or by the reaction of 1 with [Ir(CO)4]− in refluxing THF. Hydride carbonyl clusters 2–4 were fully characterized by IR and 1H NMR spectroscopies, and the molecular structures of 2 and 3 were determined by single-crystal X-ray diffraction (SC-XRD). The location of the hydride ligands within the tetrahedral cages of these clusters was further corroborated by computational studies employing DFT methods. Clusters 2–4 were tested as catalyst precursors for transfer hydrogenation on the model substrate 4-fluoroacetophenone, using iPrOH as a solvent and a hydrogen source. The results obtained using these heterometallic Ru–Ir clusters were compared to those using homometallic 1, evidencing a significant difference, particularly regarding the effect of the base on catalysis. Heterometallic cluster 2 was also tested in the hydrogenation of trans-cinnamaldehyde in iPrOH at refluxing temperature both under N2 and H2 atmospheres, and H2 pressure. [ABSTRACT FROM AUTHOR]

Heterometallic Chini-type clusters [Pt6−xNix(CO)12]2− (x = 0–6) were obtained by reactions of [Pt6(CO)12]2− with Ni-clusters such as [Ni6(CO)12]2−, [Ni9(CO)18]2− and [H2Ni12(CO)21]2−, or from [Pt9(CO)18]2− and [Ni6(CO)12]2−. The Pt/Ni composition of [Pt6−xNix(CO)12]2− (x = 0–6) depended on the nature of the reagents employed and their stoichiometry. Reactions of [Pt9(CO)18]2− with [Ni9(CO)18]2− and [H2Ni12(CO)21]2−, as well as reactions of [Pt12(CO)24]2− with [Ni6(CO)12]2−, [Ni9(CO)18]2− and [H2Ni12(CO)21]2−, afforded [Pt9−xNix(CO)18]2− (x = 0–9) species. [Pt6−xNix(CO)12]2− (x = 1–5) were converted into [Pt12−xNix(CO)21]4− (x = 2–10) upon heating in CH3CN at 80 °C, with almost complete retention of the Pt/Ni composition. Reaction of [Pt12−xNix(CO)21]4− (x ≈ 8) with HBF4·Et2O afforded the [HPt14+xNi24−x(CO)44]5− (x ≈ 0.7) nanocluster. Finally, [Pt19−xNix(CO)22]4− (x = 2–6) could be obtained by heating [Pt9−xNix(CO)18]2− (x = 1–3) in CH3CN at 80 °C, or [Pt6−xNix(CO)12]2− (2–4) in DMSO at 130 °C. The molecular structures of these new alloy nanoclusters have been determined by single crystal X-ray diffraction. The site preference of Pt and Ni within their metal cages has been computationally investigated. The electrochemical and IR spectroelectrochemical behavior of [Pt19−xNix(CO)22]4− (x = 3.11) has been studied and compared to the isostructural homometallic nanocluster [Pt19(CO)22]4−. [ABSTRACT FROM AUTHOR]

The study describes the synthesis and electrochemistry of the new Rh-centered and conjuncto rhodium carbonyl clusters. The x-ray structure of [[[NEt.sub.4]].sub.3][[Rh.sub.15][(CO).sub.27]], [[NEt.sub.4].sub.3][[Rh.sub.15][(CO).sub.25][(MeCN).sub.2]].2MeCN, and [[NEt.sub.4].sub.3][[Rh.sub.17][(CO).sub.37] is also explained.