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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]

In this review, the authors describe the role of gold in the chemistry of transition metal carbonyl clusters, a field that has been very active over the past fifty years. Both homo- and heteroleptic Au-containing species of metal carbonyl clusters, fully characterized by X-ray analysis, are discussed across three categories: those which are surface decorated by Au(I) fragments, cluster units connected by naked Au(I) atoms, and Au core–shell species with metallic gold structures embedded in the cluster frameworks. [ABSTRACT FROM AUTHOR]

This paper reports a detailed study of the oxidation and reduction reactions of simple nickel mono-carbide and mono-acetlyde carbonyl clusters. The reduction of [Ni 9 C(CO) 17 ] 2– with Na/naphtalene affords the new [Ni 12 C(CO) 18 ] 4– mono-carbide cluster. Under the same experimental conditions, [Ni 10 (C 2 )(CO) 16 ] 2– reacts with Na/naphtalene yielding a mixture of the previously reported [Ni 11 (C 2 )(CO) 15 ] 4– and [Ni 12 (C 2 )(CO) 16 ] 4– mono-acetylide tetra-anions. The oxidation reactions of both [Ni 9 C(CO) 17 ] 2– and [Ni 10 (C 2 )(CO) 16 ] 2– , carried out with miscellaneous reagents, e.g. , [C 7 H 7 ][BF 4 ], [Cp 2 Fe][PF 6 ], AgNO 3 , are more complicated and less selective, leading to mixtures of products, among which the previously reported [Ni 8 C(CO) 16 ] 2– , [Ni 16 (C 2 ) 2 (CO) 23 ] 4– , [Ni 38 C 6 (CO) 42 ] 6– and [Ni 32 C 6 (CO) 36 ] 6– species have been identified. Interestingly, oxidation of [Ni 10 (C 2 )(CO) 16 ] 2– with Pd(Et 2 S) 2 Cl 2 affords the new tetra-acetylide [Ni 22 (C 2 ) 4 (CO) 28 (Et 2 S)] 2– , even if in low yields. The new species [Ni 12 C(CO) 18 ] 4– and [Ni 22 (C 2 ) 4 (CO) 28 (Et 2 S)] 2– have been structurally characterized by means of single crystal X-ray diffraction. Electrochemical and spectroelectrochemical studies have been performed on [Ni 12 C(CO) 18 ] 4– . This compound can be electrochemically oxidized and reduced reversibly affording [Ni 12 C(CO) 18 ] 3– and [Ni 12 C(CO) 18 ] 5– , respectively. The same species can be obtained by chemical methods but, due to their limited stability during work-up, it has not been possible to isolate them. [ABSTRACT FROM AUTHOR]

The reaction of [FeC(CO){Cu(MeCN)}] ( 1) with 3 equivalents of L-L (phen or Mephen) affords [Cu(L-L)][FeC(CO){Cu(L-L)}] (L-L = phen, 2; Mephen, 3) in good yields. These are protonated by strong acids resulting in [HFeC(CO){Cu(L-L)}] (L-L = phen, 4; Mephen, 5). The reaction may be reversed with bases, resulting in the quaternary ammonium salts [NR][FeC(CO){Cu(phen)}] ( 6). 4 and 5 react with a slight excess of L-L resulting in the elimination of copper in the form of [Cu(L-L)] and formation of the previously reported [HFeC(CO)] homometallic cluster. Conversely, the reaction of 1 with a monodentate N-ligand such as quinoline, even if used in large excess, results in the substitution product [FeC(CO){Cu(quinoline)}] ( 8), which is then transformed into [Cu(Mephen)] [FeC(CO){Cu(quinoline)}] ( 9) after reaction with Mephen. By using the anionic cluster [FeC(CO){Cu(MeCN)}] instead of the neutral 1, only substitution has been observed by using both phen and quinoline, resulting in [FeC(CO){Cu(phen)}] ( 10) and [FeC(CO){Cu(quinoline)}] ( 11), respectively. Finally, the reaction of 1 with [Ru(tpy)(bpy)(NC-CH-CN)]Cl affords crystals of [FeC(CO)CuCl{Ru(tpy)(bpy)(NC-CH-CN)}] ( 12). All compounds 2-12 have been characterized by a combination of spectroscopic (IR, NMR) and crystallographic methods. All these clusters may be viewed as composed by a butterfly [FeC(CO)] core bonded to Cu(I) fragments and/or H ions. [ABSTRACT FROM AUTHOR]

The synthesis and structural characterization of [Co 5 C(CO) 11 (AuPPh 3 ) 3 ], 1 - A and 1 - B , [Co 5 C(CO) 11 (AuPPh 3 ) 2 ] − , 2 , [Co 5 C(CO) 10 (PPh 3 ) 2 (AuPPh 3 )], 3 , [Co 5 C(CO) 12 (AuPPh 3 )], 4 , [Co 5 C(CO) 11 (PPh 3 )(AuPPh 3 )], 5 , and [Co 4 C(CO) 10 (AuPPh 3 ) 2 ], 6 , is herein reported. Compounds 1 – 6 have been obtained whilst studying the reactivity of [Co 6 C(CO) 15 ] 2− with [Au(PPh 3 )Cl] under different experimental conditions, even if better alternative syntheses have been, then, found for some of these new clusters. 1 – 6 contain the electron precise [Co 5 C(CO) 12 ] − , [Co 5 C(CO) 11 ] 3− and [Co 4 C(CO) 10 ] 2− clusters, or their PPh 3 derivatives, stabilized by [AuPPh 3 ] + fragments. Two different isomers of 1 , i.e. , 1 - A and 1 - B , have been found in the solid state due to solvation effects and weak d 10 –d 10 Au(I)⋯Au(I) aurophilic interactions. 1 - A and 4 have been previously described in the literature. [ABSTRACT FROM AUTHOR]

Within the reinvestigation of Ni-Sb carbonyl cluster chemistry, we report here the synthesis and characterization of the new [Ni19Sb4(CO)26]4- cluster and the synthesis, structure, magnetic characterization and electrical resistivity of the viologen salts of the previously known [Ni13Sb2(CO)24] n- ( n = 2, 3) anionic species. The crystal structures of [NEt4]4[Ni19Sb4(CO)26], [EtV]8[Ni13Sb2(CO)24]3 ·4DMF ·2C6H14 and [EtV]3[Ni13Sb2(CO)24] ·1.5THF (EtV = 1,1′-diethyl-4,4′-bipyridilium cation, DMF = N, N-dimethylformamide, THF = tetrahydrofuran) are described. Notably, the unit cell of [EtV]8[Ni13Sb2(CO)24]3 ·4DMF ·2C6H14 involves a mixture of two [Ni13Sb2(CO)24]3- trianions and one [Ni13Sb2(CO)24]2- dianion, as it also contains eight [EtV]+ · radical monocations, which are assembled in infinite stacks. In contrast, the unit cell of the [EtV]3[Ni13Sb2(CO)24] ·1.5THF salt contains four [Ni13Sb2(CO)24]3- trianions along with twelve [EtV]+ · radical monocations, four of which are arranged into two pairs of isolated dimers, whereas the other two sets of four form two infinite stacks that extend over the whole crystal. The charges of the miscellaneous ions have been assigned on the basis of electroneutrality and spectroscopic evidence. More specifically, the infrared spectra of [EtV]8[Ni13Sb2(CO)24]3 ·4DMF ·2C6H14, both in the solid state and in solution, clearly indicate the presence of a 2:1 mixture of [Ni13Sb2(CO)24]3- and [Ni13Sb2(CO)24]2- anions. Resistivity measurements performed on pellets of powdered samples indicate that the [EtV]8[Ni13Sb2(CO)24]3 ·4DMF ·2C6H14 salt substantially behaves as an insulator. A study of the magnetic behaviour of [EtV]8[Ni13Sb2(CO)24]3 ·4DMF ·2C6H14 evidences pairing among the electrons of the EtV+ · molecules, in agreement with DFT calculations, and the odd-electron clusters behave as paramagnetic centres of spin S = 1. [ABSTRACT FROM AUTHOR]

The new bimetallic [HCo15Pd9C3(CO)38]2- tri-carbide carbonyl cluster has been obtained from the reaction of [H2Co20Pd16C4(CO)48]4- with an excess of acid in CH2Cl2 solution. The mono-hydride di-anion can be reversibly protonated and deprotonated by means of acid-base reactions leading to closely related [H3-nCo15Pd9C3(CO)38]n- (n = 0-3) clusters. The crystal structures of the three anionic and the neutral clusters have been determined as their H3Co15Pd9C3(CO)38.2thf, [NEt4][H2Co15Pd9C3(CO)38]·0.5C6H14, [NMe3(CH2Ph)]2[HCo15Pd9C3(CO)38]·C2H14 and [NEt4]3[Co15Pd9C3(CO)38]·thf salts. They are composed of a Pd9(μ3-CO)2 core stabilised by three Co5C(CO)12 organometallic fragments. The poly-hydride nature of these clusters has been indirectly inferred via chemical, electrochemical and magnetic measurements. Besides, cyclic voltammetry shows that the [H3-nCo15Pd9C3(CO)38]n- (n = 1-3) anions are multivalent, since they undergo two or three reversible oxidations. SQUID measurements of [HCo15Pd9C3(CO)38]2- indicate that this even electron cluster is paramagnetic with two unpaired electrons, giving further support to its hydride nature. Finally, structural studies show that the Pd9 core of [H3-nCo15Pd9C3(CO)38]n- (n = 0,1) is a tri-capped octahedron, which becomes a tri-capped trigonal prism in the more charged [H3-nCo15Pd9C3(CO)38]n- (n = 2,3) anions. Such a significant structural rearrangement of the metal core of a large carbonyl cluster upon protonation-deprotonation reactions is unprecedented in cluster chemistry, and suggests that interstitial hydrides may have relevant stereochemical effects even in large carbonyl clusters. [ABSTRACT FROM AUTHOR]

The state of art of the chemical, spectroscopic and structural characterization of platinum carbonyl clusters is reviewed. We begin by enlightening the fundamental contribution given to this chemistry of two great scientists: Paolo Chini and Larry Dahl, two without equal maestros of science and life. We then focus the main body of this review on the challenge represented by studying molecular ions already belonging to the nano regime by size almost 50 years ago, and the challenges their chemistry continues to present also nowadays. In detail, the possible reasons which enable the [Pt(CO)] oligomers to grow up to n = 10, and why the oligomers with n > 5 may self-assemble in infinite molecular conductor wires are suggested. The interplay between the CO/Pt ratios and electronic effects in driving the platinum cluster from pseudo one- to tri-dimensional globular structures, often representing chunks of the fcc metal lattice or interpenetrated pentagonal prisms and icosahedra, is examined by means of two significant examples. The nanocapacitor behavior of most high-nuclearity carbonyl clusters is briefly recalled and is confirmed by most recent results. The size-induced transition of their metal kernels from insulator to semiconductor and the expected consequences of their eventual transition to a metallic state are also discussed. Finally, we conclude by commenting the present lack of Pt cluster interstitially lodging a main group element and not yet quantitatively-assessed aggregation phenomena in solution, perhaps peculiar of ionic salts of carbonyl clusters, which could make undetectable the NMR signal of any spin-active nuclei beyond a cluster nuclearity of ca. 20-25. [ABSTRACT FROM AUTHOR]

The reaction of [Pt12(CO)24]2- with CH2═C(PPh2)2 (P∧P) results in the neutral tetrahedral cluster Pt4(CO)4(P∧P)2. This reacts with strong acids such as HBF4 to afford, first, the [HPt4(CO)4(P∧P)2]+ monohydride monocation and, then, the [H2Pt4(CO)4(P∧P)2]2+ dihydride dication. The three clusters have been fully characterized in solution by means of IR and ¹H and 31P NMR spectroscopy. Both Pt4(CO)4(P∧P)2 and [H2Pt4(CO)4(P∧P)2]2+ are static in solution, whereas [HPt4(CO)4(P∧P)2]+ displays a fluxional behavior of the unique hydride ligand. In addition, the molecular structures of all these clusters have been fully determined in the solid state via single-crystal X-ray diffraction, showing that all of them possess the same 56-electron tetrahedral Pt4(CO)4(P∧P)2 core to which the hydride ligands are added stepwise. [ABSTRACT FROM AUTHOR]

The Ni6C(CO)9(AuPPh3)4 bimetallic carbide carbonyl cluster was obtained from the reaction of [Ni9C(CO)17]2- with Au(PPh3)Cl. It contains a rare carbon-centered (distorted) Ni6C octahedral core decorated by four Au(PPh3) fragments. These are μ3-bonded to four contiguous Ni3-triangular faces and display weak intramolecular Au···Au d10-d10 interactions. The cluster has been characterized in the solid state on two different solvato crystals, i.e., Ni6C(CO)9(AuPPh3)4·THF and Ni6C(CO)9(AuPPh3)4·THF·0.5C6H14. The two solvates show some interesting differences concerning the weak Au···Au contacts. Density functional theory calculations have demonstrated that the presence of the two isomers is related to solid-state packing effects and not to the existence of two double minima in the potential energy surface. This, in turn, confirms that Au···Au d10-d10 interactions are rather soft and thus influenced also by weak van der Waals forces because of the interaction of the cluster with the cocrystallized solvent molecules. [ABSTRACT FROM AUTHOR]

A detailed study of the reaction between [Ni6(CO)12]2- and [AuCl4]⁻ afforded the isolation of the new Ni--Au cluster [Ni12Au(CO)24]3- as well as identifying an improved synthesis for the previously reported [Ni32Au6(CO)44]6-. The new [Ni12Au(CO)24]3- cluster is composed by two [Ni6(CO)12]2- moieties coordinated to a central Au(I) ion, as determined by X-ray diffraction. It is noteworthy that the two [Ni6(CO)12]2- fragments display different geometries, i.e., trigonal antiprismatic (distorted octahedral) and distorted trigonal prismatic (monocapped square pyramidal). The chemical reactivity of these clusters and their electrochemical behavior have been studied. [Ni12Au(CO)24]3- is irreversibly transformed, upon electrochemical reduction, into Au(0) and [Ni6(CO)12]2-, followed by the reversible reduction of the latter homometallic cluster. Conversely, [Ni32Au6(CO)44]6- displays five reductions, with apparent features of reversibility, confirming the ability of larger metal carbonyl clusters to reversibly accept and release electrons. [ABSTRACT FROM AUTHOR]

The reaction of [CO6C(CO)15]2 with 2 equiv of PtCI2(Et2S)2 affords the new heterobimetallic [CO8Pt4C2(CO)24]2-, [1]2-, carbonyl cluster. [1]2- undergoes reversible chemical and electrochemical oxidation and reduction processes disclosing a complete series of [1]n (n = 1-4) clusters. The monoand dianion of [1]n- have been isolated as their tetra-substituted ammonium salts and fully characterized by means of IR, 13C NMR, ESI-MS, and X-ray crystallography. Variable-temperature (VT) solid-state EPA studies on pure crystalline samples indicate that both [1]2- and [1]→ are paramagnetic, due to a doublet state of the latter and a triplet state of [1]2-. This conclusion is supported by SQUID measurements on the same crystalline sample of [1]2-. The present study indisputably demonstrates that even-electron transition metal carbonyl clusters (TMCC) can be magnetic. [ABSTRACT FROM AUTHOR]

The new tetra-acetylide carbonyl clusters [H4−nNi22(C2)4(CO)28(CdBr)2]n−(n= 2–4) have been prepared by reacting [Ni10C2(CO)15]2−with a large excess of CdBr2·xH2O and the molecular structure of the di-anion [H2Ni22(C2)4(CO)28(CdBr)2]2−has been fully elucidated by means of X-ray crystallography. The corresponding [HNi22(C2)4(CO)28(CdBr)2]3−and [Ni22(C2)4(CO)28(CdBr)2]4−conjugated bases are quantitatively obtained upon dissolution of [H2Ni22(C2)4(CO)28(CdBr)2]2−salts in more basic solvents such as acetonitrile and DMSO, respectively. The hydride nature of both [H2Ni22(C2)4(CO)28(CdBr)2]2−and [HNi22(C2)4(CO)28(CdBr)2]3−has been directly proved by 1H NMR spectroscopy. Their resonances are very broad under all experimental conditions and their chemical shift greatly depends on solvent as well as temperature. Observation of the hydride resonances in [H4−nNi22(C2)4(CO)28(CdBr)2]n−(n= 2, 3) makes these clusters a case study of the phenomena behind the loss of any NMR signal in higher-nuclearity metal carbonyl cluster anions (MCCA). In the attempt to obtain a better insight on this experimental spectroscopic behaviour, solutions of [NMe4]3[HNi22(C2)4(CO)28(CdBr)2] have been investigated by dynamic light scattering (DLS) at various concentrations. The DLS experiments point out the presence in solution of a distribution of particles with nominal hydrodynamic diameters enormously greater than those of the free cluster ions resulting, probably, from aggregation in solution. This could formally justify the observed NMR behaviour, even if the present observations are preliminary and their quantitative assessment requires further systematic studies on MCCA aggregation in solution. [ABSTRACT FROM AUTHOR]

Abstract: The reaction in MeCN of [Ag5Fe4(CO)16]3– in its Na+ salt with EtV2+ 2I– leads to precipitation of [EtV+•]5[Ag13Fe8(CO)32]. Its DMF solution is deep-green, displays infrared carbonyl absorptions very similar to those of the paramagnetic [Ag13Fe8(CO)32]4– tetraanion and only shows the EPR signal of the EtV+• radical cation. The colour of the solution and the IR spectrum suggest the presence of a charge–transfer salt. Crystallisation of the precipitate from DMF and isopropyl alcohol affords brown crystals of [EtV+•]5[Ag13Fe8(CO)32]·4 DMF, which are insoluble in all organic solvents, DMF included. X-ray analysis of the crystals provided the structure of the yet uncharacterised [Ag13Fe8(CO)32]5– pentaanion and allowed the first determination of the structure of the ethylviologen radical cation. The latter gives rise to stacks in which weakly-bound pentameric moieties are clearly identifiable. The structural findings are implemented by spectroscopic measurements and EHMO calculations. To cite this article: D. Collini et al., C. R. Chimie 8 (2005) . [Copyright &y& Elsevier]

The reaction of the [Ni6(CO)12]2− dianion with [Rh(COD)Cl]2 (COD=cyclooctadiene) in excess affords a complicate mixture of bimetallic Ni&z.sbnd;Rh clusters, from which the new [NiRh5(CO)14]3− and [NiRh14(CO)28]4− have been isolated and characterised. The [NiRh14(CO)28]4− tetraanionic cluster has been also obtained from reacting [Ni2Rh12(CO)25]4− and [NiRh13(CO)25]5− with [Rh(CO)2Cl]2, whereas [NiRh5(CO)14]3− has been more conveniently obtained by reduction with alkali metals or hydroxides of [NiRh5(CO)15]−. All these new bimetallic Ni&z.sbnd;Rh carbonyl clusters have been isolated in the solid state as tetrasubstituted ammonium salts and were characterised by elemental analysis, spectroscopy and X ray diffraction studies. The structure of the diamagnetic [NiRh5(CO)14]3− trianion is identical to that of the homometallic [Co6(CO)14]4− tetraanion, the unique Ni atom being disordered over the 6 equiv. trigonal antiprismatic sites. The [NiRh5(CO)14]3− trianion is slowly and irreversibly degraded to a mixture of Ni(CO)4, [Rh(CO)4]− and [Rh7(CO)16]3− upon exposure to an atmosphere of carbon monoxide. The [NiRh14(CO)28]4− tetranion displays a metal frame consisting in a hexacapped cube of rhodium atoms centered by the unique nickel atom. This metal frame has previously been found in the homometallic [Rh15(CO)30]3− cluster. However, at difference from the latter, [NiRh14(CO)28]4− features two less valence electrons and displays a shrinked cubic moiety. [NiRh14(CO)28]4− is slowly degraded by carbon monoxide and halide ions to give [NiRh13(CO)25]5− and other yet uncharacterised Ni&z.sbnd;Rh carbonyl clusters. All above Ni&z.sbnd;Rh clusters do not display protonation behaviour. [Copyright &y& Elsevier]

Examines the chemical and electrochemical redox behavior of the bimetallic anion clusters. Electron-sink features of the metal carbonyl clusters; Differences between the electrochemical responses of the ions in the extra oxidation process; Synthesis and characterization of pentaanion; Role of nuclearity on the average separations of the atoms.

The reaction of [Ni 10 (C 2 ) (CO) 16 ] 2– with CuCl in thf affords [Ni 45 C 10 (CO) 46 ] 6– as the major product. This represents the first deca-carbide carbonyl cluster and this is the highest number of C-atoms found in a molecular cluster. Besides, the new octa-carbide [HNi 42 C 8 (CO) 44 (CuCl)] 7– and the previously reported tetra-carbide [Ni 34+x C 4 (CO) 38+x ] 6– (x = 0,1) have been obtained as side-products. Whilst studying the reactions of miscellaneous Ni carbide clusters with Cu(I) salts in the search for a better synthesis of [HNi 42 C 8 (CO) 44 (CuCl)] 7– , the homoleptic [Ni 32+x C 6 (CO) 36+x ] 6– (x = 0–2) and the heteroleptic [Ni 38 C 6 (CO) 36 (MeCN) 6 (CuMeCN) 2x ] 2– clusters have been isolated in low yields. By analysing the Ni carbide clusters herein reported as well as those previously described in the literature, it results that they are built-up starting from four fundamental building blocks: octahedral Oh-Ni 6 C, trigonal prismatic TP-Ni 6 C, capped trigonal prismatic cTP-Ni 7 C and square anti-prismatic SA-Ni 8 C. These may be joined into larger Ni x C y metal-carbide frameworks by sharing vertices, edges or faces. Even though infinite combinations are possible, some Ni x C y motives are common to two or more clusters, envisioning a possible rationale behind their building-up. [ABSTRACT FROM AUTHOR]

Thereaction of [HFe4(CO)12]3–(1) with [Ir(COD)Cl]2results in the formationof the bimetallic Fe–Ir monohydride carbonyl cluster [HFe4(CO)12(IrCOD)]2–(2). This is quantitatively protonated by strong acids to the dihydride[H2Fe4(CO)12(IrCOD)]−(3). Further addition of acids to 3resultsin the tetranuclear dihydride [H2Fe3(CO)10(IrCOD)]−(4) via formal oxidativeelimination of a Fe(CO)2fragment. Compounds 2–4have been fully characterized by means of 1H VT NMR spectroscopy, X-ray crystallography, and DFT calculations.In 2and 3the Fe4Ir clustercore adopts a trigonal bipyramidal geometry, while the Fe3Ir core in 4is tetrahedral. In addition, 1H VT NMR studies indicate that 2and 3arefluxional in solution, whereas 4is not. [ABSTRACT FROM AUTHOR]

Nanometric CoPd bimetallic [H6− nCo20Pd16C4(CO)48] n− ( n=3-6) tetracarbide carbonyl clusters have been prepared by redox condensation of [Co6C(CO)15]2− with [PdCl2(Et2S)2]. The crystal structures of both the dihydride tetra-anion and monohydride penta-anion have been determined as their [NEt4]4[H2Co20Pd16C4(CO)48] ⋅4 CH3COCH3 and [NMe3(CH2Ph)][NMe4]4[HCo20Pd16C4(CO)48] ⋅5 CH3COCH3 salts, respectively. The two species are isostructural and their structures display a perfect segregation of the two metals. They are composed of a cubic close-packed (ccp) Pd16 core stabilised on its surface by four {Co5C(CO)12} organometallic fragments. Their polyhydride nature has been corroborated by the study of their reactions with acids and bases, and confirmed by electrochemical studies. In addition, the reactions of [H2Co20Pd16C4(CO)48]4− with Na/naphthalene and PPh3/CO allowed the isolation of other lower nuclearity homoleptic and heteroleptic clusters, that is, [H6− nCo16Pd2C3(CO)28] n− ( n=5, 6), [Co4Pd2C(CO)11(PPh3)2], [Co2Pd5C(CO)8(PPh3)5], and [Co4Pd4C2(PPh3)4(CO)10Cl]−. [H6− nCo16Pd2C3(CO)28] n− ( n=5, 6) represent the first homoleptic metal-carbonyl clusters containing three interstitial carbide atoms. [ABSTRACT FROM AUTHOR]

The thermal decomposition in thf solution of [H2Ni22Co6C6(CO)36]4− results in the new [HNi36Co8C8(CO)48]5− bimetallic Ni–Co octa-carbide, which can be converted into the closely related [H6−nNi36Co8C8(CO)48]n− (n = 3–6) polyhydrides by means of acid–base reactions. The structure of the [Ni36Co8C8(CO)48]6− hexa-anion has been established via X-ray crystallography, showing that the eight interstitial carbide atoms are lodged within different metal cages. Thus, two C-atoms are enclosed within regular square anti-prismatic Ni8C cages, four within irregular Ni8C square anti-prismatic cages, and the last two within mono-capped trigonal prismatic Ni5Co2C cages. The structure of [Ni36Co8C8(CO)48]6− is non-compact and closely related to [Ni32C6(CO)38]6− and [HNi38C6(CO)44]5−. [Ni36Co8C8(CO)48]6− approaches the nanosize regime and the whole molecular ion has a diameter (measured from the outer oxygen atoms) of ca. 1.61 nm. [ABSTRACT FROM AUTHOR]

The reduction of [Fe6C(CO)16]2- (1) with NaOH in DMSO or with Na/naphthalene in THF affords the highly reduced [Fe6C(CO)15] 4- (2) monocarbide tetraanion. The molecular structure of 2 has been crystallographically determined as its [Et4N]4[Fe6C(CO)15]·CH3CN salt, revealing an octahedral structure as expected for a hexanuclear cluster possessing 86 valence electrons. The stepwise protonation of 2 with strong acids such as HBF4·Et2O results first in the monohydride trianion [HFe6C(CO)15]3- (3) and then the purported dihydride dianion [H2Fe6C(CO)15]2- (4), as indicated by ¹H NMR spectroscopy. Both 3 and 4 are not stable enough to be isolated and rapidly decompose, yielding the parent dianion 1. The reaction of 2 with a slight excess of Au(PPh3)Cl affords the aurated dianion [Fe6C(CO)15(AuPPh3)2]2- (5), which has been isolated and structurally characterized as its [Et4N]2[Fe6C(CO)15(AuPPh3)2]·2CH3CN salt. DFT calculations allowed us to study, from a computational point of view, the electronic features of the new compounds and possible reaction intermediates. [ABSTRACT FROM AUTHOR]

A reinvestigation of the synthesis of [H5-nRh13(CO)24]n- (n = 2, 3) led to isolation of a senes of Rh19, Rh26, and Rh33 high-nuclearity carbonyl and carbonyl-substituted rhodium clusters. The [Rh19(CO)31]5- ( l ) is electronically equivalent with [Pt19(CO)22]4-, but poor crystal diffraction data of all salts obtained to date have prevented its geometrical analysis. The structures of Rh26(CO)29(CH3CN)11 (2) as 2 . 2 C H 3 C N and [ R h 3 3 ( C O ) 4 7 ] 5- ( 3 ) as [NEt4]5[3].Me2CO were determined from complete X-ray diffraction determinations. The latter two species adopt polyicosahedral metal frameworks, and notably, [Rh33(CO)47]5- represents the molecular group 9 metal carbonyl cluster of highest nuclearity so far reported. [ABSTRACT FROM AUTHOR]

The article focuses on the characterization of Iron-carbonyl-protected Gold clusters in 2009. Molecular electronics, optical labels for biomolecules and precursor for catalysts contain ligand-stabilized nanometer-sized gold particles. GPAW code was utilized to investigate the NIR response and electronic structure of cluster compounds 1-5. Perdew-Burke-Ernzerhof 10a was used to calculate the exchange correlation interaction.