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New high-nuclearity Ni-Pt carbonyl clusters: synthesis and X-ray structure of the ordered [Ni24Pt14(CO)44]4- and the substitutionally Ni/Pt disordered [Ni10(Ni6-xPtx)Pt8(CO)30]4- (x = 1.92) tetraanions
No full textThe reaction of [(NBu4)-Bu-n](2)[Ni-6(CO)(12)] in THF solution with 1.5-2 equivalents of K2PtCl4 leads to formation of the [Ni24Pt14(CO)(44)](4-) and [Ni-10(Ni6-xPtx)Pt-8(CO)(30)](4-) (x approximate to2) tetraanions, the latter presents a localised substitutional NY Pt disorder and an unprecedented close-packed metal structure
Further insights into platinum carbonyl Chini clusters
No full textThe oxidation of [Ph3P(CH2)12PPh3][Pt15(CO)30] with CF3COOH in THF afforded [Ph3P(CH2)12PPh3][Pt18(CO)36] as a precipitate which was re-crystallized from dmf/isopropanol. This salt self-assembles in the solid state adopting an unprecedented morphology which consists of infinite chains of [Pt9(CO)18]− units. The solid state structure of [Ph3P(CH2)12PPh3][Pt18(CO)36] may be viewed as a snapshot in which [Pt9(CO)18]− units are approaching and ready to exchange outer Pt3(CO)6 fragments. The reactions of Chini clusters with isonitriles proceed via redox-fragmentation, at difference with those involving phosphines that may occur both via non-redox substitution and redox fragmentation, depending on the experimental conditions. Thus, the reaction of [Pt6(CO)12]2− with CNXyl afforded Pt5(CNXyl)10, whereas Pt9(CNXyl)13(CO) was obtained from the reaction of [Pt15(CO)30]2− with CNXyl. These two new neutral clusters have been structurally characterized as their Pt5(CNXyl)10·2toluene and Pt9(CNXyl)13(CO)·solv solvates. DFT studies on the CO exchange of [Pt6(CO)12]2− suggest an associative interchange mechanism, which may be extended also to larger Chini clusters and the initial steps of their reactions with other soft nucleophiles
Atomically Precise Ni-Pd Alloy Carbonyl Nanoclusters: Synthesis, Total Structure, Electrochemistry, Spectroelectrochemistry, and Electrochemical Impedance Spectroscopy
Full text linkThe molecular nanocluster [Ni36-xPd5+x(CO)46]6- (x = 0.41) (16-) was obtained from the reaction of [NMe3(CH2Ph)]2[Ni6(CO)12] with 0.8 molar equivalent of [Pd(CH3CN)4][BF4]2 in tetrahydrofuran (thf). In contrast, [Ni37-xPd7+x(CO)48]6- (x = 0.69) (26-) and [HNi37-xPd7+x(CO)48]5- (x = 0.53) (35-) were obtained from the reactions of [NBu4]2[Ni6(CO)12] with 0.9-1.0 molar equivalent of [Pd(CH3CN)4][BF4]2 in thf. After workup, 35- was extracted in acetone, whereas 26- was soluble in CH3CN. The total structures of 16-, 26-, and 35- were determined with atomic precision by single-crystal X-ray diffraction. Their metal cores adopted cubic close packed structures and displayed both substitutional and compositional disorder, in light of the fact that some positions could be occupied by either Ni or Pd. The redox behavior of these new Ni-Pd molecular alloy nanoclusters was investigated by cyclic voltammetry and in situ infrared spectroelectrochemistry. All three compounds 16-, 26-, and 35- displayed several reversible redox processes and behaved as electron sinks and molecular nanocapacitors. Moreover, to gain insight into the factors that affect the current-potential profiles, cyclic voltammograms were recorded at both Pt and glassy carbon working electrodes and electrochemical impedance spectroscopy experiments performed for the first time on molecular carbonyl nanoclusters
Nickel poly-acetylide carbonyl clusters: structural features, bonding and electrochemical behaviour
No full textThe reactions of [NEt 4] 2[Ni 6(CO) 12] with miscellaneous carbon halides (e.g. CCl 4, C 4Cl 6) in CH 2Cl 2 have been extensively investigated particularly focusing on the stoichiometric ratio of the reagents and reaction temperature. This allowed the preparation of the previously known acetylide clusters [Ni 16(C 2) 2(CO) 23] 4-, [HNi 25(C 2) 4(CO) 32] 3- and [Ni 22(C 2) 4(CO) 28Cl] 3-, as well as isolation and full characterisation of the closely related [Ni 17(C 2) 2(CO) 24] 4- and [Ni 25(C 2) 4(CO) 32] 4- tetraanions. From a structural point of view, all these clusters are based on a Ni 16 square orthobicupola which contain interstitial C 2, Ni(η 2-C 2) 4 or Ni 2(μ- η 2-C 2) 4 moieties, displaying rather short C-C bonds. Electrochemical studies reveal that all these species undergo different redox processes, even if their stability is rather limited. This is corroborated by an extensive analysis of the interaction between interstitial C 2 acetylide units and the metal cluster cage by Extended Huckel Molecular Orbital (EHMO) calculations, which indicates that tightly bonded C-C units are less effective than isolated C-atoms in stabilising the cluster cag
Cage rearrangements in dodecanuclear Co-Pt dicarbido clusters promoted by redox reactions
No full textThe chemical reduction of [Co8Pt4C2(CO)24]2– ([1]2–) with Na/naphthalene results, after workup, in the isolation of either [Co10Pt2C2(CO)22]4– ([2]4–) or [Co8Pt4C2(CO)20]4– ([3]4–), depending on the experimental conditions. All these species undergo several chemical and/or electrochemical redox reactions, disclosing the existence of structurally related dodecanuclear clusters [1]n– (n = 0–4), [2]n– (n = 2–6) and [3]n–(n = 1–7). In the attempt to isolate more reduced species,[1]n–, [2]n– and [3]n– undergo structural rearrangements resulting, among others, in the formation of the new species [Co10–xPt2+xC2(CO)24]2– ([4]2–) (x = 0–2) structurally related to [1]2–. These dodecanuclear M12C2 dicarbido clusters are not isostructural and differ in the metal composition and/or the number of CO ligands. Nevertheless, they can be readily interconverted even if the interconversion reactions are not straightforward
Redox active Ni-Pd carbonyl alloy nanoclusters: syntheses, molecular structures and electrochemistry of [Ni22-xPd20+x(CO)48]6-(x= 0.62), [Ni29-xPd6+x(CO)42]6-(x= 0.09) and [Ni29+xPd6-x(CO)42]6-(x= 0.27)
Full text linkA redox active Ni-Pd alloy nanocluster [Ni22-xPd20+x(CO)48]6-(x= 0.62) ([>1>]6-) was obtained from the redox condensation of [NBu4]2[Ni6(CO)12] with 0.7-0.8 equivalents of Pd(Et2S)2Cl2in CH2Cl2. Conversely, [Ni29-xPd6+x(CO)42]6-(x= 0.09) ([>2>]6-) and [Ni29+xPd6-x(CO)42]6-(x= 0.27) ([>3>]6-) were obtained by employing [NEt4]2[Ni6(CO)12] and 0.6-0.7 equivalents of Pd(Et2S)2Cl2in CH3CN. The molecular structures of these high nuclearity Ni-Pd carbonyl clusters were determined by single-crystal X-ray diffraction (SC-XRD). [>1>]6-adopted an M40ccpstructure comprising five close-packed ABCAB layers capped by two additional Ni atoms. Conversely, [>2>]6-and [>3>]6-displayed anhcpM35metal core composed of three compact ABA layers. [>1>]6-, [>2>]6-and [>3>]6-showed nanometric sizes, with the maximum lengths of their metal cores being 1.3 nm ([>1>]6-) and 1.0 nm ([>2>]6-and [>3>]6-), which increased up to 1.9 and 1.5 nm, after including also the CO ligands. Ni-Pd distribution within their metal cores was achieved by avoiding terminal Pd-CO bonding and minimizing Pd-CO coordination. As a consequence, site preference and partial metal segregation were observed, as well as some substitutional and compositional disorders. Electrochemical and spectroelectrochemical studies revealed that [>1>]6-and [>2>]6-were redox active and displayed four and three stable oxidation states, respectively. Even though several redox active high nuclearity metal carbonyl clusters have been previously reported, the nanoclusters described herein represent the first examples of redox active Ni-Pd carbonyl alloy nanoclusters
One-pot atmospheric pressure synthesis of [H3Ru4(CO)12]−
Full text linkReductive carbonylation of RuCl3·3H2O at CO-atmospheric pressure results in the [H3Ru4(CO)12]−(1) polyhydride carbonyl cluster. The one-pot synthesis involves the following steps: heating RuCl3·3H2O at 80 °C in 2-ethoxyethanol for 2 h, addition of three equivalents of KOH, heating at 135 °C for 2 h, addition of a fourth equivalent of KOH and heating at 135 °C for 1 h. The resulting K[1] salt is transformed into [NEt4][1] upon metathesis with [NEt4]Br in H2O. The IR,1H and13C{1H} NMR spectroscopic data are in agreement with those reported in the literature. [Ru8(CO)16(X)4(CO3)4]4−(X = Cl, Br, I;2-X) is formed as a by-product during the synthesis of1, and the two compounds are separated on the basis of their different solubilities in organic solvents. The nature of the halide of2-Xdepends on the [NEt4]X salt used for metathesis.2-Bris transformed into [Ru10(CO)20(Br)4(CO3)4]2−(3) upon reaction with an excess of HBF4·Et2O.1is readily deprotonated by strong bases affording the previously known [H2Ru4(CO)12]2−(4). The reaction of1with [Cu(MeCN)4][BF4] affords [H3Ru4(CO)12(CuMeCN)] (7), whereas [H2Ru4(CO)12(CuBr)2]2−(8) is obtained from the reaction of4with [Cu(MeCN)4][BF4]/[NEt4]Br. All the compounds have been spectroscopically characterized, their molecular structures determined by single crystal X-ray diffraction (SC-XRD) and investigated using DFT methods in selected cases in order to confirm the hydride positions and to study the relative stability of possible isomers
The Magnetic Behaviour of the [NBu4]4[Ni16Pd16(CO)40] Salt: An Even-Electron Homoleptic Carbonyl Metal Cluster Anion Displaying a J = 2 Ground State
No full textHighly Reduced Ruthenium Carbide Carbonyl Clusters: Synthesis, Molecular Structure, Reactivity, Electrochemistry, and Computational Investigation of [Ru6C(CO)15]4-
Full text linkThe 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
Isomerism in Molecular Metal Carbonyl Clusters
No full textThe 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
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