Molecular nickel poly-carbide carbonyl nanoclusters: The octa-carbide [HNi42C8(CO)44(CuCl)]7– and the deca-carbide [Ni45C10(CO)46]6–

Highly Reduced Ruthenium Carbide Carbonyl Clusters: Synthesis, Molecular Structure, Reactivity, Electrochemistry, and Computational Investigation of [Ru6C(CO)15]4

The reaction of [Ru6C(CO)16]2- (1) with NaOH in DMSO resulted in the formation of a highly reduced [Ru6C(CO)15]4- (2), which was readily protonated by acids, such as HBF4·Et2O, to [HRu6C(CO)15]3- (3). Oxidation of 2 with [Cp2Fe][PF6] or [C7H7][BF4] in CH3CN resulted in [Ru6C(CO)15(CH3CN)]2- (5), which was quantitatively converted into 1 after exposure to CO atmosphere. The reaction of 2 with a mild methylating agent such as CH3,I afforded the purported [Ru6C(CO)14(COCH3)]3- (6). By employing a stronger reagent, that is, CF3SO3CH3, a mixture of [HRu6C(CO)16]- (4), [H3Ru6C(CO)15]- (7), and [Ru6C(CO)15(CH3CNCH3)]- (8) was obtained. The molecular structures of 2-5, 7, and 8 were determined by single-crystal X-ray diffraction as their [NEt4]4[2]·CH3CN, [NEt4]3[3], [NEt4][4], [NEt4]2[5], [NEt4][7], and [NEt4][8]·solv salts. The carbyne-carbide cluster 6 was partially characterized by IR spectroscopy and ESI-MS, and its structure was computationally predicted using DFT methods. The redox behavior of 2 and 3 was investigated by electrochemical and IR spectroelectrochemical methods. Computational studies were performed in order to unravel structural and thermodynamic aspects of these octahedral Ru-carbide carbonyl clusters displaying miscellaneous ligands and charges in comparison with related iron derivatives.

From M6 to M12, M19 and M38 molecular alloy Pt-Ni carbonyl nanoclusters: selective growth of atomically precise heterometallic nanoclusters

Heterometallic Chini-type clusters [Pt_6-xNi_x(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 [Pt_6-xNi_x(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 [Pt_9-xNi_x(CO)₁₈]^2- (x = 0-9) species. [Pt_6-xNi_x(CO)₁₂]^2- (x = 1-5) were converted into [Pt_12-xNi_x(CO)₂₁]^4- (x = 2-10) upon heating in CH₃CN at 80 °C, with almost complete retention of the Pt/Ni composition. Reaction of [Pt_12-xNi_x(CO)₂₁]^4- (x ≈ 8) with HBF₄·Et₂O afforded the [HPt_14+xNi_24-x(CO)₄₄]^5- (x ≈ 0.7) nanocluster. Finally, [Pt_19-xNi_x(CO)₂₂]^4- (x = 2-6) could be obtained by heating [Pt_9-xNi_x(CO)₁₈]^2- (x = 1-3) in CH₃CN at 80 °C, or [Pt_6-xNi_x(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 [Pt_19-xNi_x(CO)₂₂]^4- (x = 3.11) has been studied and compared to the isostructural homometallic nanocluster [Pt₁₉(CO)₂₂]^4-.

Platonic and Archimedean solids in discrete metal-containing clusters

Metal-containing clusters have attracted increasing attention over the past 2-3 decades. This intense interest can be attributed to the fact that these discrete metal aggregates, whose atomically precise structures are resolved by single-crystal X-ray diffraction (SCXRD), often possess intriguing geometrical features (high symmetry, aesthetically pleasing shapes and architectures) and fascinating physical properties, providing invaluable opportunities for the intersection of different disciplines including chemistry, physics, mathematical geometry and materials science. In this review, we attempt to reinterpret and connect these fascinating clusters from the perspective of Platonic and Archimedean solid characteristics, focusing on highly symmetrical and complex metal-containing (metal = Al, Ti, V, Mo, W, U, Mn, Fe, Co, Ni, Pd, Pt, Cu, Ag, Au, lanthanoids (Ln), and actinoids) high-nuclearity clusters, including metal-oxo/hydroxide/chalcogenide clusters and metal clusters (with metal-metal binding) protected by surface organic ligands, such as thiolate, phosphine, alkynyl, carbonyl and nitrogen/oxygen donor ligands. Furthermore, we present the symmetrical beauty of metal cluster structures and the geometrical similarity of different types of clusters and provide a large number of examples to show how to accurately describe the metal clusters from the perspective of highly symmetrical polyhedra. Finally, knowledge and further insights into the design and synthesis of unknown metal clusters are put forward by summarizing these "star" molecules.

Structural Chemistry of Giant Metal Based Supramolecules

The review presents a bird-eye view on the state of research in the field of giant nonbiological discrete metal complexes and ions of nanometer size, which are structurally characterized by means of single-crystal X-ray diffraction, using the crystal structure as a common key feature. The discussion is focused on the main structural features of the metal clusters, the clusters containing compact metal oxide/hydroxide/chalcogenide core, ligand-based metal-organic cages, and supramolecules as well as on the aspects related to the packing of the molecules or ions in the crystal and the methodological aspects of the single-crystal neutron and X-ray diffraction of these compounds.

Metal carbonyl clusters of groups 8-10: synthesis and catalysis

In this review article, we discuss advances in the chemistry of metal carbonyl clusters (MCCs) spanning the last three decades, with an emphasis on the more recent reports and those involving groups 8-10 elements. Synthetic methods have advanced and been refined, leading to higher-nuclearity clusters and a wider array of structures and nuclearities. Our understanding of the electronic structure in MCCs has advanced to a point where molecular chemistry tools and other advanced tools can probe their properties at a level of detail that surpasses that possible with other nanomaterials and solid-state materials. MCCs therefore advance our understanding of structure-property-reactivity correlations in other higher-nuclearity materials. With respect to catalysis, this article focuses only on homogeneous applications, but it includes both thermally and electrochemically driven catalysis. Applications in thermally driven catalysis have found success where the reaction conditions stabilise the compounds toward loss of CO. In more recent years, MCCs, which exhibit delocalised bonding and possess many electron-withdrawing CO ligands, have emerged as very stable and effective for reductive electrocatalysis reactions since reduction often strengthens M-C(O) bonds and since room-temperature reaction conditions are sufficient for driving the electrocatalysis.

Structural Diversity in Molecular Nickel Phosphide Carbonyl Nanoclusters

The reaction of [Ni₆(CO)₁₂]^2– as a [NBu₄]⁺ salt in CH₂Cl₂ with 0.8 equiv of PCl₃ afforded [Ni₁₄P₂(CO)₂₂]^2–. In contrast, the reactions of [Ni₆(CO)₁₂]^2– as a [NEt₄]⁺ salt with 0.4–0.5 equiv of POCl₃ afforded [Ni_22–xP₂(CO)_29–x]^4– (x = 0.84) or [Ni₃₉P₃(CO)₄₄]^6– by using CH₃CN and thf as a solvent, respectively. Moreover, by using 0.7–0.9 mol of POCl₃ per mole of [NEt₄]₂[Ni₆(CO)₁₂] both in CH₃CN and thf, [Ni_23–xP₂(CO)_30–x]^4– (x = 0.82) was obtained together with [Ni₂₂P₆(CO)₃₀]^2– as a side product. [Ni_23–xP₂(CO)_30–x]^4– (x = 0.82) and [Ni₂₂P₆(CO)₃₀]^2– were separated owing to their different solubility in organic solvents. All the new molecular nickel phosphide carbonyl nanoclusters were structurally characterized through single crystal X-ray diffraction (SC-XRD) as [NBu₄]₂[Ni₁₄P₂(CO)₂₂] (two different polymorphs, P2₁/n and C2/c), [NEt₄]₄[Ni_23–xP₂(CO)_30–x]·CH₃COCH₃·solv (x = 0.82), [NEt₄]₂[Ni₂₂P₆(CO)₃₀]·2thf, [NEt₄]₄[Ni_22–xP₂(CO)_29–x]·2CH₃COCH₃( x = 0.84) and [NEt₄]₆[Ni₃₉P₃(CO)₄₄]·C₆H₁₄·solv. The metal cores’ sizes of these clusters range from 0.59 to 1.10 nm, and their overall dimensions including the CO ligands are 1.16–1.63 nm. In this respect, they are comparable to ultrasmall metal nanoparticles, molecular nanoclusters, or atomically precise metal nanoparticles. The environment of the P atoms within these molecular Ni–P–CO nanoclusters displays a rich diversity, that is, Ni₅P pentagonal pyramid, Ni₇P monocapped trigonal prism, Ni₈P bicapped trigonal prism, Ni₉P monocapped square antiprism, Ni₁₀P sphenocorona, Ni₁₀P bicapped square antiprism, and Ni₁₂P icosahedron.

Five new molecular nickel phosphide carbonyl clusters have been obtained displaying overall sizes in the range 1.16−1.63 nm and very diverse environments for the phosphide atoms.

Molecular Nickel Phosphide Carbonyl Nanoclusters: Synthesis, Structure, and Electrochemistry of [Ni11P(CO)18]3- and [H6-nNi31P4(CO)39]n- (n = 4 and 5)

The reaction of [NEt₄]₂[Ni₆(CO)₁₂] in thf with 0.5 equiv of PCl₃ affords the monophosphide [Ni₁₁P(CO)₁₈]^3- that in turn further reacts with PCl₃ resulting in the tetra-phosphide carbonyl cluster [HNi₃₁P₄(CO)₃₉]^5-. Alternatively, the latter can be obtained from the reaction of [NEt₄]₂[Ni₆(CO)₁₂] in thf with 0.8-0.9 equiv of PCl₃. The [HNi₃₁P₄(CO)₃₉]^5- penta-anion is reversibly protonated by strong acids leading to the [H₂Ni₃₁P₄(CO)₃₉]^4- tetra-anion, whereas deprotonation affords the [Ni₃₁P₄(CO)₃₉]^6- hexa-anion. The latter is reduced with Na/naphthalene yielding the [Ni₃₁P₄(CO)₃₉]^7- hepta-anion. In order to shed light on the polyhydride nature and redox behavior of these clusters, electrochemical and spectroelectrochemical studies were carried out on [Ni₁₁P(CO)₁₈]^3-, [HNi₃₁P₄(CO)₃₉]^5-, and [H₂Ni₃₁P₄(CO)₃₉]^4-. The reversible formation of the stable [Ni₁₁P(CO)₁₈]^4- tetra-anion is demonstrated through the spectroelectrochemical investigation of [Ni₁₁P(CO)₁₈]^3-. The redox changes of [HNi₃₁P₄(CO)₃₉]^5- show features of chemical reversibility and the vibrational spectra in the ν_CO region of the nine redox states of the cluster [HNi₃₁P₄(CO)₃₉]^n- (n = 3-11) are reported. The spectroelectrochemical investigation of [H₂Ni₃₁P₄(CO)₃₉]^4- revealed the presence of three chemically reversible reduction processes, and the IR spectra of [H₂Ni₃₁P₄(CO)₃₉]^n- (n = 4-7) have been recorded. The different spectroelectrochemical behavior of [HNi₃₁P₄(CO)₃₉]^5- and [H₂Ni₃₁P₄(CO)₃₉]^4- support their formulations as polyhydrides. Unfortunately, all the attempts to directly confirm their poly hydrido nature by ¹H NMR spectroscopy failed, as previously found for related large metal carbonyl clusters. Thus, the presence and number of hydride ligands have been based on the observed protonation/deprotonation reactions and the spectroelectrochemical experiments. The molecular structures of the new clusters have been determined by single-crystal X-ray analysis. These represent the first examples of structurally characterized molecular nickel carbonyl nanoclusters containing interstitial phosphide atoms.