Globular molecular platinum carbonyl nanoclusters: Synthesis and molecular structures of the [Pt 26 (CO) 32 ] − and [Pt 14+x (CO) 18+x ] 4− anions and their comparison to related platinum “browns”

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.

Atomically Precise Platinum Carbonyl Nanoclusters: Synthesis, Total Structure, and Electrochemical Investigation of [Pt27(CO)31]4- Displaying a Defective Structure

The molecular Pt nanocluster [Pt₂₇(CO)₃₁]^4– (1^4–) was obtained by thermal decomposition of [Pt₁₅(CO)₃₀]^2– in tetrahydrofuran under a H₂ atmosphere. The reaction of 1^4– with increasing amounts of HBF₄·Et₂O afforded the previously reported [Pt₂₆(CO)₃₂]^2– (3^2–) and [Pt₂₆(CO)₃₂]⁻ (3^–). The new nanocluster 1^4– was characterized by IR and UV–visible spectroscopy, single-crystal X-ray diffraction, direct-current superconducting quantum interference device magnetometry, cyclic voltammetry, IR spectroelectrochemistry (IR SEC), and electrochemical impedance spectroscopy. The cluster displays a cubic-close-packed Pt₂₇ framework generated by the overlapping of four ABCA layers, composed of 3, 7, 11, and 6 atoms, respectively, that encapsulates a fully interstitial Pt₄ tetrahedron. One Pt atom is missing within layer 3, and this defect (vacancy) generates local deformations within layers 2 and 3. These local deformations tend to repair the defect (missing atom) and increase the number of Pt–Pt bonding contacts, minimizing the total energy. The cluster 1^4– is perfectly diamagnetic and displays a rich electrochemical behavior. Indeed, six different oxidation states have been characterized by IR SEC, unraveling the series of 1^n– (n = 3–8) isostructural nanoclusters. Computational studies have been carried out to further support the interpretation of the experimental data.

The synthesis, molecular structure, magnetic properties, computational investigation, electrochemical and IR spectroelectrochemical behavior, and electrochemical impedance spectroscopy investigation of the new multivalent [Pt₂₇(CO)₃₁]⁴⁻ nanocluster are reported.

Looking at platinum carbonyl nanoclusters as superatoms

Although the chemistry of carbonyl-protected platinum nanoclusters is well established, their bonding mode remains poorly understood. In most of them, the average Pt oxidation state is zero or slightly negative, leading to the apparent average configuration 5d¹⁰ 6s^ε (ε = 0 or very small) and the apparent conclusion that metal-metal bonding cannot arise from the completely filled 5d shell nor from the empty (or almost empty) 6s orbitals. However, DFT calculations show in fact that in these species the actual average configuration is 5d^10-x 6s^x, which provides to the whole cluster a significant total number of 6s electrons that ensures metal-metal bonding. This ("excited") average configuration is to be related to that of coinage metals in ligated group 11 nanoclusters (nd¹⁰ (n + 1)s^x). Calculations show that metal-metal bonding in most of these platinum nanoclusters can be rationalized within the concepts of superatoms and supermolecules, in a similar way as for group 11 nanoclusters. The "excited" 5d^10-x 6s^x configuration results from a level crossing between 5d combinations and 6s combinations, the former transferring their electrons to the latter. This level crossing, which does not exist in the bare Pt_n clusters, is induced by the ligand shell, the role of which being thus not innocent with respect to metal-metal bonding.

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.

Synthesis of [Pt12(CO)20(dppm)2]2- and [Pt18(CO)30(dppm)3]2- Heteroleptic Chini-type Platinum Clusters by the Oxidative Oligomerization of [Pt6(CO)12(dppm)]2

The reactions of [Pt₆(CO)₁₂]^2- with CH(PPh₂)₂ (dppm), CH₂═C(PPh₂)₂ (P^P), and Fe(C₅H₄PPh₂)₂ (dppf) proceed via nonredox substitution and result in the heteroleptic Chini-type clusters [Pt₆(CO)₁₀(dppm)]^2-, [Pt₆(CO)₁₀(P^P)]^2-, and [Pt₆(CO)₁₀(dppf)]^2-, respectively. Conversely, the reactions of [Pt₆(CO)₁₂]^2- with Ph₂P(CH₂)₄PPh₂ (dppb) and Ph₂PC≡CPPh₂ (dppa) can be described as redox fragmentation that afford the neutral complexes Pt(dppb)₂, Pt₂(CO)₂(dppa)₃, and Pt₈(CO)₆(PPh₂)₂(C≡CPPh₂)₂(dppa)₂. The oxidation of [Pt₆(CO)₁₀(dppm)]^2- results in its oligomerization to yield the larger heteroleptic Chini-type clusters [Pt₁₂(CO)₂₀(dppm)₂]^2-, [Pt₁₈(CO)₃₀(dppm)₃]^2-, and [Pt₂₄(CO)₄₀(dppm)₄]^2- (for the latter there is only IR spectroscopic evidence). All the clusters were characterized by means of IR and ³¹P NMR spectroscopies and electrospray ionization mass spectrometry. Moreover, the crystal structures of [NEt₄]₂[Pt₆(CO)₁₀(dppm)]·CH₃CN, [NEt₄]₂[Pt₁₂(CO)₂₀(dppm)₂]·2CH₃CN·2dmf, [NEt₄]₂[Pt₁₂(CO)₂₀(dppm)₂]·4dmf, [NEt₄]₂[Pt₆(CO)₁₀(dppf)]·2CH₃CN, Pt₂(CO)₂(dppa)₃·0.5CH₃CN, Pt₈(CO)₆(PPh₂)₂(C≡CPPh₂)₂(dppa)₂·2thf, and Pt(dppb)₂ were determined by single-crystal diffraction (dmf = dimethylformamide; thf = tetrahydrofuran).