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The reaction of Collman's reagent Na2[Fe(CO)4]·2thf with one equivalent of Au(NHC)Cl (NHC = IMes, IPr; IMes = C3N2H2(C6H2Me3)2; IPr = C3N2H2(C6H3iPr2)2) in dmso resulted in the [Fe(CO)4(AuNHC)]– (NHC = IMes, 1; IPr, 2) mono‐anions. 1–2 further reacted with Au(NHC)Cl or Au(PPh3)Cl affording the neutral complexes Fe(CO)4(AuNHC)2 (NHC = IMes, 3; IPr, 4), Fe(CO)4(AuIMes)(AuIPr) (5) and Fe(CO)4(AuNHC)(AuPPh3) (NHC = IMes, 6; IPr, 7). 1–7 have been spectroscopically characterized by IR, 1H, 13C{1H} and 31P{1H} NMR techniques. Moreover, the molecular structures of 1, 2, 4, 6 and 7 have been determined through single‐crystal X‐ray diffraction as their [NMe4][Fe(CO)4(AuIMes)], [NEt4][Fe(CO)4(AuIMes)], [NEt4][Fe(CO)4(AuIPr)], Fe(CO)4(AuIPr)2·1.5toluene, Fe(CO)4(AuIPr)(AuPPh3), Fe(CO)4(AuIMes)(AuPPh3)·0.5CH2Cl2 salts and solvates. The nature of the bonds in 1 and 2 was elucidated on the basis of atoms‐in molecules (AIM) analyses on the DFT‐optimized structures and compared with the corresponding compounds 3 and 4. 1–7 contained strong Fe‐CO, Fe‐Au, Au‐P and Au–NHC bonds as well as weak Au···Au interactions. The different stability and reactivity of IMes‐derivatives vs. IPr‐ones was rationalized on the basis of steric effects. [ABSTRACT FROM AUTHOR]

The reactions of [Pt3n(CO)6n]2− (n = 2–5) homoleptic Chini-type clusters with increasing amounts of 1,3,5-triaza-7-phosphaadamantane (PTA) result in the stepwise substitution of one terminal CO ligand per Pt3 triangular unit up to the formation of [Pt3n(CO)5n(PTA)n]2− (n = 2–5). Competition between the nonredox substitution with retention of the nuclearity and the redox fragmentation to afford lower nuclearity heteroleptic Chini-type clusters is observed as a function of the amount of PTA and the nuclearity of the starting cluster. Because of this, [Pt12(CO)20(PTA)4]2− and [Pt15(CO)25(PTA)5]2− are more conveniently obtained via the oxidation of [Pt9(CO)15(PTA)3]2−. All the new species were spectroscopically characterized, and the structures of [Pt12(CO)20(PTA)4]2− and [Pt15(CO)25(PTA)5]2− were determined by single-crystal X-ray diffraction. These clusters may be viewed as heteroleptic Chini-type clusters composed of stacks of four and five Pt3(μ-CO)3(CO)2(PTA) units, respectively. The solubility in water of [Pt12(CO)20(PTA)4]2− and [Pt15(CO)25(PTA)5]2− has been determined and their cytotoxicity towards human ovarian (A2780) cancer cells and their cisplatin-resistant strain (A2780cisR) has been evaluated. [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]

The reaction of the Collman's reagent NaFe(CO) with two equivalents of Au(NHC)Cl (NHC = IMes, IPr, IBu) in thf results in the bimetallic Fe(CO)(AuNHC) (NHC = IMes, 2; IPr, 3; IBu, 4; IMes = CNH(CHMe); IPr = CNH(CHPr); IBu = CNH(CMe)) clusters in good yields. Heating 2 in dmf at 100 °C results in the higher nuclearity cluster [AuFe(CO)(IMes)] ( 5). 2- 5 have been fully characterized via IR, H and C NMR spectroscopies and their structures determined by means of single crystal X-ray crystallography. Gas-phase DFT calculations were carried out on 2- 5 and the model compound cis-Fe(CO)(AuIDM) ( 6) (IDM = CNHMe), in order to better understand the metal-metal and metal-ligand interactions in these compounds without the influence of packing forces. [ABSTRACT FROM AUTHOR]

The reaction of [Pt15(CO)30]2− with increasing amounts of SnCl2 affords [Pt8(CO)10(SnCl2)4]2− (2), [Pt10(CO)14{Cl2Sn(OH)SnCl2}2]2− (5), [Pt6(CO)6(SnCl2)2(SnCl3)4]4− (3), [Pt9(CO)8(SnCl2)3(SnCl3)2(Cl2SnOCOSnCl2)]4− (4) and [Pt5(CO)5{Cl2Sn(OR)SnCl2}3]3− (R = H, Me, Et, and iPr) (1-R). 1-R and 2 have been previously described, whereas 3–5 are herein reported for the first time. The species 1–3 are the main products of the reaction under different experimental conditions, whereas 4 and 5 are by-products of the synthesis of 3 and 2, respectively. From a structural point of view, the clusters 1–5 all show a perfect segregation of the two metals, which are composed of a low valent Pt core decorated on the surface by Sn(ii) fragments such as SnCl2, [SnCl3]−, [Cl2Sn(OH)SnCl2]− and [Cl2SnOCOSnCl2]2−. These fragments behave as two electron donor ligands via each Sn-atom (and also the C-atom in the case of [Cl2SnOCOSnCl2]2−). The [Cl2SnOCOSnCl2]2− ligand is rather unique and may be viewed as a bis-stannyl-carboxylate, a carbon dioxide μ3:k3-C,O,O′-CO2 or a carbonite ion [CO2]2− stabilized by coordination to metal atoms. Compounds 1–5 have been fully characterised via IR spectroscopy, X-ray crystallography and DFT calculations. [ABSTRACT FROM AUTHOR]

Abstract: 1,3-Dipolar cycloaddition of nitrile imines with α,β-unsaturated five- and six-membered lactones, thiolactones and lactams gave ring-fused pyrazoles. Regioisomeric mixtures have been obtained with the 5-substituted pyrazole as the major cycloadduct. Only with the five-membered lactone the major product was the 4-acyl derivative. Computational studies, the use of the topological analysis of the Fukui functions and the potential energy surfaces (PES) theory allowed a theoretical description of the local reactivity in agreement with the observed high regiochemistry and with the role of the heteroatom adjacent to the carbonyl group. [Copyright &y& Elsevier]

Abstract: Tetrachloroauric acid HAuCl4 reacts with the ionic liquid 1-(2-aminoethyl)-3-methylimidazolium nitrate [NH2(CH2)2ImMe]NO3, (2b) or its dicationic ammonium salt [NH3(CH2)2ImMe][NO3]2, (3) in methanolic solutions to give the novel gold(III)-aminoethyl imidazolium aurate salt [Cl3AuNH2(CH2)2ImMe][AuCl4] (4). The reaction of 4 with [ n Bu4]Cl gives [NH2(CH2)2ImMe][AuCl4] (2c) whereas with acetone the dicationic, iminium-functionalized, imidazolium aurate salt [Me2C=N(H)(CH2)2ImMe][AuCl4]2 (5) has been isolated. The structures in the solid state of 2c, 3, 4, and 5 have been determined by X-ray diffraction. The electrochemical behaviour of 4 has been examined by Cyclic voltammetry in acetonitrile and compared with 2c and KAuCl4. [Copyright &y& Elsevier]

Abstract: A series of supported gold/iron catalysts has been prepared from bimetallic carbonyl clusters and characterized to determine how the nature of the precursors and the thermal treatment conditions affected the dispersion of the active phase and the catalytic activity. The chemical–physical characterization, and the catalytic tests carried out, evidenced that the deposition of bimetallic Au/Fe carbonyl clusters on a titania support, and their following controlled decomposition, is a way to obtain stable catalysts, active in the decomposition of toluene. [Copyright &y& Elsevier]

The tributyltin esters of 4-(ethyl)-phenyl-ethanoic acid and 4-(isopropyl)-phenyl-ethanoic acid have been prepared as model compounds of the repeating unit of the related stannylated polystyrenic derivatives. Both the products were fully characterized by proton and carbon NMR two-dimensional techniques. FT-IR spectra show in the solid state carboxylated moieties bridging R3Sn groups with the metal atom expanding its coordination number, this structure being destroyed in solution. The supramolecular arrangement of the products in the solid state has been investigated by X-ray diffraction, which confirms the pentacoordination at tin in both the products, and indicates a different spatial arrangement of the alkylated aryl groups, as evidenced also by the slightly different thermal properties. [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.

A new self-assembly morphology, the reactions with isonitriles and a DFT study on the CO exchange of Chini clusters are reported. • A new self-assembly morphology of Chini clusters is reported. • [Pt 9 (CO) 18 ]− units are approaching and ready to exchange outer Pt 3 (CO) 6 fragments. • The reaction of Chini clusters with isonitriles proceeds via redox-fragmentation. • DFT studies on the CO exchange of [Pt 6 (CO) 12 ]2− suggests an associative interchange mechanism. The oxidation of [Ph 3 P(CH 2) 12 PPh 3 ][Pt 15 (CO) 30 ] with CF 3 COOH in THF afforded [Ph 3 P(CH 2) 12 PPh 3 ][Pt 18 (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 [Pt 9 (CO) 18 ]− units. The solid state structure of [Ph 3 P(CH 2) 12 PPh 3 ][Pt 18 (CO) 36 ] may be viewed as a snapshot in which [Pt 9 (CO) 18 ]− units are approaching and ready to exchange outer Pt 3 (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 [Pt 6 (CO) 12 ]2− with CNXyl afforded Pt 5 (CNXyl) 10 , whereas Pt 9 (CNXyl) 13 (CO) was obtained from the reaction of [Pt 15 (CO) 30 ]2− with CNXyl. These two new neutral clusters have been structurally characterized as their Pt 5 (CNXyl) 10 · 2toluene and Pt 9 (CNXyl) 13 (CO) · solv solvates. DFT studies on the CO exchange of [Pt 6 (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. [ABSTRACT FROM AUTHOR]

The acid-induced synthesis of low valent Pt carbonyl clusters decorated by Sn(II) fragments was reported. • The acid-induced rearrangement of Pt–Sn molecular clusters is reported. • These molecular clusters show a perfect segregation of the two metals. • Sn(II) fragments act as two electron donor ligands. • Structural and theoretical evidence of the ability of Sn-fragments to stabilise molecular clusters and nanoclusters. The reactions of [Pt 6 (CO) 6 (SnX 2) 2 (SnX 3) 4 4– (X = Cl, 1 ; Br, 2) with an excess of HBF 4 · Et 2 O afforded the new [Pt 12 (CO) 10 (SnCl) 2 (SnCl 2) 4 {Cl 2 Sn(μ-OH)SnCl 2 } 2 2– (3) and [Pt 7 (CO) 6 (SnBr 2) 4 {Br 2 Sn(μ-OH)SnBr 2 }{Br 2 Sn(μ-Br)SnBr 2 }]2– (4) heterometallic clusters. The molecular structures of 3 and 4 were determined by means of single crystal X-ray diffraction. The bonding within these bimetallic Pt–Sn clusters were investigated computationally by means of DFT methods and Atoms-In-Molecules analyses. 3 and 4 displayed a low valent Pt core stabilised by the interaction with CO and Sn(II) based ligands. The solid state structures of these clusters revealed the presence on H-bonds involving the OH-groups of the {X 2 Sn(μ-OH)SnX 2 }– ligands. [ABSTRACT FROM AUTHOR]

In this Frontier Article, the work carried out within our research group in Bologna in the field of surface decorated metal carbonyl clusters will be outlined and put in a more general context. After a short Introduction, clusters composed of a metal carbonyl core decorated on the surface by metal-ligand fragments will be analyzed. Both metal-ligand fragments behaving as Lewis acids and Lewis bases will be considered. Then, the focus will be moved to clusters composed of a naked metal core decorated and stabilized on the surface by metal-carbonyl fragments. The structure and bonding (where theoretical studies are available) of such surface decorated metal carbonyl clusters will be presented, and compared to atomically precise ligated nanoclusters.

In this paper we present the investigation of the reactivity of [Rh 7 (CO) 16 ] 3- with InCl 3 , with the aim of expanding the more general study that allowed us to obtain, among other species, the icosahedral [Rh 12 E(CO) 27 ] n - ( n = 4 when E = Ge or Sn; n = 3 when E = Sb or Bi) family of clusters. Indeed, the study resulted in the isolation and characterization of the analogous In-centred icosahedral [Rh 12 In(CO) 28 ] 3- nanocluster (1), which is isoelectronic and isostructural with the [Rh 12 E(CO) 27 ] n - congeners. During the course of the reaction two more new species, namely the octahedral [Rh 6 (CO) 15 InCl 3 ] 2- (2) and the dimeric [{Rh 6 (CO) 15 InCl 2 } 2 ] 2- (3) have also been identified. The reaction between [Rh 7 (CO) 16 ] 3- and InCl 3 proved to be poorly selective; nevertheless, by fine tuning some reaction parameters it was possible to drive the reaction more towards one product or the other. Alternatively, [Rh 6 (CO) 15 InCl 3 ] 2- can be more selectively prepared by reacting either [Rh 5 (CO) 15 ] - or, less efficiently, [Rh 6 (CO) 15 ] 2- with InCl 3 . As for the dimeric [{Rh 6 (CO) 15 InCl 2 } 2 ] 2- species, this was only isolated by carrying out the reaction with [Rh 7 (CO) 16 ] 3- under inert atmosphere, as opposed to under CO. All clusters were characterized by IR spectroscopy and ESI-MS, and their molecular structures were fully established by single-crystal X-ray diffraction studies. The [Rh 12 In(CO) 28 ] 3- species was also analysed by EDS via SEM, and further investigated through in situ infrared spectroelectrochemistry and CV experiments to check its multivalence nature. Indeed, [Rh 12 In(CO) 28 ] 3- can reversibly undergo two monoelectronic oxidation and one bi-electronic reduction processes, behaving like an electron sponge and, thus, giving rise to the further [Rh 12 In(CO) 28 ] n - derivatives ( n = 1, 2 and 5). These results parallel the findings for the [Rh 12 E(CO) 27 ] n - series. The geometry variations of the metal framework associated with the changes in the cluster negative charge were investigated by means of DFT calculations.

The stepwise addition of increasing amounts of Au(PPh 3 )Cl to [HRu 4 (CO) 12 ] 3- (1) results in the sequential formation of [HRu 4 (CO) 12 (AuPPh 3 )] 2- (2), [HRu 4 (CO) 12 (AuPPh 3 ) 2 ] - (3), and HRu 4 (CO) 12 (AuPPh 3 ) 3 (4). Alternatively, 4 can be obtained upon addition of HBF 4 ·Et 2 O (two mole equivalents) to 3. Further addition of acid to 3 (three mole equivalents) results in the formation of the tetra-aurated cluster Ru 4 (CO) 12 (AuPPh 3 ) 4 (5). Compounds 2-5 have been characterized by IR, 1 H and 31 P{ 1 H} NMR spectroscopies. Moreover, the molecular structures of 3-5 have been determined by single crystal X-ray diffraction as [NEt 4 ][3]·2CH 2 Cl 2 , 4-b·2CH 2 Cl 2 , 4-a, 5·0.5CH 2 Cl 2 ·solv, and 5·solv crystalline solids. Two different isomers of 4, that is 4-a and 4-b, have been crystallographically characterized and their rapid interconversion in solution was studied by variable temperature 1 H and 31 P{ 1 H} NMR spectroscopies. Weak aurophilic Au⋯Au contacts have been detected in the solid state structures of 3-5. Computational studies have been performed in order to elucidate bonding and isomerism, as well as to predict the possible structure of the elusive species 2.

The reaction of [Ru 6 C(CO) 16 ] 2- ( 1 ) with NaOH in DMSO resulted in the formation of a highly reduced [Ru 6 C(CO) 15 ] 4- ( 2 ), which was readily protonated by acids, such as HBF 4 ·Et 2 O, to [HRu 6 C(CO) 15 ] 3- ( 3 ). Oxidation of 2 with [Cp 2 Fe][PF 6 ] or [C 7 H 7 ][BF 4 ] in CH 3 CN resulted in [Ru 6 C(CO) 15 (CH 3 CN)] 2- ( 5 ), which was quantitatively converted into 1 after exposure to CO atmosphere. The reaction of 2 with a mild methylating agent such as CH 3, I afforded the purported [Ru 6 C(CO) 14 (COCH 3 )] 3- ( 6 ). By employing a stronger reagent, that is, CF 3 SO 3 CH 3 , a mixture of [HRu 6 C(CO) 16 ] - ( 4 ), [H 3 Ru 6 C(CO) 15 ] - ( 7 ), and [Ru 6 C(CO) 15 (CH 3 CNCH 3 )] - ( 8 ) was obtained. The molecular structures of 2-5 , 7 , and 8 were determined by single-crystal X-ray diffraction as their [NEt 4 ] 4 [ 2 ]·CH 3 CN, [NEt 4 ] 3 [ 3 ], [NEt 4 ][ 4 ], [NEt 4 ] 2 [ 5 ], [NEt 4 ][ 7 ], and [NEt 4 ][ 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.

In this paper, we present a comparative study of the redox properties of the icosahedral [Rh 12 E(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 [Rh 12 Ge(CO) 27 ] 4- (1), [Rh 12 Sb(CO) 27 ] 3- (3), and [Rh 12 Bi(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 [Rh 12 Sn(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 [Rh 12 Sb(CO) 27 ] 3- , we were able to isolate a new species, namely, [Rh 11 Sb(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.

The direct reactions of homometallic [Ni 6 (CO) 12 ] 2- and [Pt 6 (CO) 12 ] 2- Chini carbonyl clusters result in heterometallic Ni-Pt Chini-type clusters of the general formula [Pt 6- x Ni x (CO) 12 ] 2- ( x = 0-6). Their molecular structures have been determined by single-crystal X-ray diffraction (SC-XRD), showing a common octahedral (staggered, D 3 d ) structure analogous to that of [Ni 6 (CO) 12 ] 2- , whereas [Pt 6 (CO) 12 ] 2- displays a trigonal-prismatic (eclipsed, D 3 h ) structure. This structural change after replacing one single Pt with Ni may be classified as an alloying effect, and it has been theoretically investigated by DFT methods. Spectroscopic (IR and 195 Pt and 13 C NMR) and ESI-MS studies indicate that mixtures of [Pt 6- x Ni x (CO) 12 ] 2- ( x = 0-6) clusters are actually present in solution, whose compositions may be varied in an almost continuous way. Thus, they may be viewed as random alloy clusters whose overall compositions depend on the stoichiometry of the reagents.

The reaction of [Ni 6 (CO) 12 ] 2- as a [NBu 4 ] + salt in CH 2 Cl 2 with 0.8 equiv of PCl 3 afforded [Ni 14 P 2 (CO) 22 ] 2- . In contrast, the reactions of [Ni 6 (CO) 12 ] 2- as a [NEt 4 ] + salt with 0.4-0.5 equiv of POCl 3 afforded [Ni 22- x P 2 (CO) 29- x ] 4- ( x = 0.84) or [Ni 39 P 3 (CO) 44 ] 6- by using CH 3 CN and thf as a solvent, respectively. Moreover, by using 0.7-0.9 mol of POCl 3 per mole of [NEt 4 ] 2 [Ni 6 (CO) 12 ] both in CH 3 CN and thf, [Ni 23- x P 2 (CO) 30- x ] 4- ( x = 0.82) was obtained together with [Ni 22 P 6 (CO) 30 ] 2- as a side product. [Ni 23- x P 2 (CO) 30- x ] 4- ( x = 0.82) and [Ni 22 P 6 (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 [NBu 4 ] 2 [Ni 14 P 2 (CO) 22 ] (two different polymorphs, P 2 1 / n and C 2/ c ), [NEt 4 ] 4 [Ni 23- x P 2 (CO) 30- x ]·CH 3 COCH 3 ·solv ( x = 0.82), [NEt 4 ] 2 [Ni 22 P 6 (CO) 30 ]·2thf, [NEt 4 ] 4 [Ni 22- x P 2 (CO) 29- x ]·2CH 3 COCH 3 ( x = 0.84) and [NEt 4 ] 6 [Ni 39 P 3 (CO) 44 ]·C 6 H 14 ·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, Ni 5 P pentagonal pyramid, Ni 7 P monocapped trigonal prism, Ni 8 P bicapped trigonal prism, Ni 9 P monocapped square antiprism, Ni 10 P sphenocorona, Ni 10 P bicapped square antiprism, and Ni 12 P icosahedron.

Miscellaneous 2-D molecular alloy clusters of the type [M x M' 5- x Fe 4 (CO) 16 ] 3- (M, M' = Cu, Ag, Au; M ≠ M') have been prepared through the reactions of [Cu 3 Fe 3 (CO) 12 ] 3- , [Ag 4 Fe 4 (CO) 16 ] 4- or [M 5 Fe 4 (CO) 16 ] 3- (M = Cu, Ag) with M'(I) salts (M' = Cu, Ag, Au). Their formation involves a combination of oxidation, condensation, and substitution reactions. The total structures of several [M x M' 5- x Fe 4 (CO) 16 ] 3- clusters with different compositions have been determined by means of single crystal X-ray diffraction (SC-XRD) and their nature in solution elucidated by electron spray ionization mass spectrometry (ESI-MS) and IR and UV-visible spectroscopy. Substitutional and compositional disorder is present in the solid state structures, and ESI-MS analyses point out that mixtures of isostructural clusters differing by a few M/M' coinage metals are present. SC-XRD studies indicate some site preferences of the coinage metals within the metal cores of these clusters, with Au preferentially in corner sites and Cu in the central site. DFT studies give theoretical support to the experimental structural evidence. The site preference is mainly dictated by the strength of the Fe-M bonds that decreases in the order Fe-Au > Fe-Ag > Fe-Cu, and the preferred structure is the one that maximizes the number of stronger Fe-M interactions. Overall, the molecular nature of these clusters allows their structures to be fully revealed with atomic precision, resulting in the elucidation of the bonding parameters that determine the distribution of the different metals within their metal cores.

The reactivity of [Rh 7 (CO) 16 ] 3- with SbCl 3 has been deeply investigated with the aim of finding a new approach to prepare atomically precise metalloid clusters. In particular, by varying the stoichiometric ratios, the reaction atmosphere (carbon monoxide or nitrogen), the solvent, and by working at room temperature and low pressure, we were able to prepare two large carbonyl clusters of nanometer size, namely, [Rh 20 Sb 3 (CO) 36 ] 3- and [Rh 21 Sb 2 (CO) 38 ] 5- . A third large species composed of 28 metal atoms was isolated, but its exact formulation in terms of metal stoichiometry could not be incontrovertibly confirmed. We also adopted an alternative approach to synthesize nanoclusters, by decomposing the already known [Rh 12 Sb(CO) 27 ] 3- species with PPh 3 , willing to generate unsaturated fragments that could condense to larger species. This strategy resulted in the formation of the lower-nuclearity [Rh 10 Sb(CO) 21 PPh 3 ] 3- heteroleptic cluster instead. All three new compounds were characterized by IR spectroscopy, and their molecular structures were fully established by single-crystal X-ray diffraction studies. These showed a distinct propensity for such clusters to adopt an icosahedral-based geometry. Their characterization was completed by ESI-MS and NMR studies. The electronic properties of the high-yield [Rh 21 Sb 2 (CO) 38 ] 5- cluster were studied through cyclic voltammetry and in situ infrared spectroelectrochemistry, and the obtained results indicate a multivalent nature.

The thermal reactions of [NEt 4 ][Fe(CO) 4 (AuNHC)] [NHC = IMes ([NEt 4 ][ 1 ]) or IPr ([NEt 4 ][ 2 ]); IMes = C 3 N 2 H 2 (C 6 H 2 Me 3 ) 2 ; IPr = C 3 N 2 H 2 (C 6 H 3 i Pr 2 ) 2 ], Fe(CO) 4 (AuNHC) 2 [NHC = IMes ( 3 ) or IPr ( 4 )], Fe(CO) 4 (AuIMes)(AuIPr) ( 5 ), and Fe(CO) 4 (AuNHC)(AuPPh 3 ) [NHC = IMes ( 6 ) or IPr ( 7 )] were investigated in different solvents [CH 2 Cl 2 , CH 3 CN, dimethylformamide, and dimethyl sulfoxide (dmso)] and at different temperatures (50-160 °C) in an attempt to obtain higher-nuclearity clusters. 1 and 2 completely decomposed in refluxing CH 2 Cl 2 , resulting in [Fe 2 (CO) 8 (AuNHC)] - [NHC = IMes ( 10 ) or IPr ( 11 )]. Traces of [Fe 3 (CO) 10 (CCH 3 )] - ( 12 ) were obtained as a side product. Conversely, 6 decomposed in refluxing CH 3 CN, affording the new cluster [Au 3 {Fe(CO) 4 } 2 (PPh 3 ) 2 ] - ( 15 ). The relative stability of the two isomers found in the solid state structure of 15 was computationally investigated. 4 was very stable, and only after prolonged heating above 150 °C in dmso was limited decomposition observed, affording small amounts of [Fe 3 S(CO) 9 ] 2- ( 9 ), [HFe(CO) 4 ] - ( 16 ), and [Au 16 S{Fe(CO) 4 } 4 (IPr) 4 ] n + ( 17 ). A dicationic nature for 17 was proposed on the basis of density functional theory calculations. All of the other reactions examined led to species that were previously reported. The molecular structures of the new clusters 11 , 12 , 15 , and 17 were determined by single-crystal X-ray diffraction as their [NEt 4 ][ 11 ]·1.5toluene, [Au(IMes) 2 ][ 15 ]·0.67CH 2 Cl 2 , [NEt 4 ][ 12 ], and [ 17 ][BF 4 ] n ·solvent salts, respectively.

Triangular clusters [{MFe(CO) 4 } 3 ] 3- (M = Cu, 4; Ag, 5; Au, 6) were selectively obtained by heating Fe(CO) 4 (MIMes) 2 (M = Cu, 1; Ag, 2; Au, 3; IMes = C 3 N 2 H 2 (C 6 H 2 Me 3 ) 2 ). 1-3 were synthesized by reacting Na 2 [Fe(CO) 4 ]·2thf with 2 equiv of M(IMes)Cl. As previously described, the direct reactions of Na 2 [Fe(CO) 4 ]·2thf with one equivalent of M(I) salts resulted in the triangular cluster [{CuFe(CO) 4 } 3 ] 3- for Cu, whereas the square clusters [{MFe(CO) 4 } 4 ] 4- were formed for Ag and Au. Thus, depending on the synthetic protocol adopted, both the triangular [{MFe(CO) 4 } 3 ] 3- and square [{MFe(CO) 4 } 4 ] 4- polymerization isomers can be selectively obtained, at least for Ag and Au. Polymerization isomerism, that is two compounds having the same elemental compositions but different molecular weights, was investigated in [{MFe(CO) 4 } n ] n- ( n = 3, 4; M = Cu, Ag, Au) by means of structural and theoretical methods and the role of metallophilic interactions was computationally studied by means of the atoms-in-molecules (AIM) approach.

This article describes a rare case of cluster core isomerism in a large molecular organometallic nanocluster. In particular, two isomers of the [HCo 15 Pd 9 C 3 (CO) 38 ] 2- nanocluster, referred as TP-Pd 9 and Oh-Pd 9 , have been structurally characterized by single-crystal X-ray crystallography as their [NMe 3 (CH 2 Ph)] 2 [HCo 15 Pd 9 C 3 (CO) 38 ]·CH 2 Cl 2 (ca. 1:1 TP-Pd 9 and Oh-Pd 9 mixture), [NMe 3 (CH 2 Ph)] 2 [HCo 15 Pd 9 C 3 (CO) 38 ]·2CH 2 Cl 2 (mainly TP-Pd 9 ), [NEt 3 (CH 2 Ph)] 2 [HCo 15 Pd 9 C 3 (CO) 38 ]·CH 2 Cl 2 (mainly TP-Pd 9 ), [MePPh 3 ] 2 [HCo 15 Pd 9 C 3 (CO) 38 ]·2.5CH 2 Cl 2 (mainly TP-Pd 9 ), and [MePPh 3 ] 2 [HCo 15 Pd 9 C 3 (CO) 38 ] (Oh-Pd 9 ) salts. The cluster core of TP-Pd 9 is a tricapped trigonal prism, whereas this is a tricapped octahedron in Oh-Pd 9 . The presence in the solid state of the Oh-Pd 9 or TP-Pd 9 isomers depends on the cation employed and/or the number and type of co-crystallized solvent molecules. Often, mixtures of the two isomers, within the same single crystal or as mixtures of different crystals within the same crystallization batch, are obtained. Structural isomerism in organometallic nanoclusters is discussed and compared to that in Au-thiolate nanoclusters., Competing Interests: The authors declare no competing financial interest.

The reactions of [Pt 6 (CO) 12 ] 2- with CH(PPh 2 ) 2 (dppm), CH 2 ═C(PPh 2 ) 2 (P^P), and Fe(C 5 H 4 PPh 2 ) 2 (dppf) proceed via nonredox substitution and result in the heteroleptic Chini-type clusters [Pt 6 (CO) 10 (dppm)] 2- , [Pt 6 (CO) 10 (P^P)] 2- , and [Pt 6 (CO) 10 (dppf)] 2- , respectively. Conversely, the reactions of [Pt 6 (CO) 12 ] 2- with Ph 2 P(CH 2 ) 4 PPh 2 (dppb) and Ph 2 PC≡CPPh 2 (dppa) can be described as redox fragmentation that afford the neutral complexes Pt(dppb) 2 , Pt 2 (CO) 2 (dppa) 3 , and Pt 8 (CO) 6 (PPh 2 ) 2 (C≡CPPh 2 ) 2 (dppa) 2 . The oxidation of [Pt 6 (CO) 10 (dppm)] 2- results in its oligomerization to yield the larger heteroleptic Chini-type clusters [Pt 12 (CO) 20 (dppm) 2 ] 2- , [Pt 18 (CO) 30 (dppm) 3 ] 2- , and [Pt 24 (CO) 40 (dppm) 4 ] 2- (for the latter there is only IR spectroscopic evidence). All the clusters were characterized by means of IR and 31 P NMR spectroscopies and electrospray ionization mass spectrometry. Moreover, the crystal structures of [NEt 4 ] 2 [Pt 6 (CO) 10 (dppm)]·CH 3 CN, [NEt 4 ] 2 [Pt 12 (CO) 20 (dppm) 2 ]·2CH 3 CN·2dmf, [NEt 4 ] 2 [Pt 12 (CO) 20 (dppm) 2 ]·4dmf, [NEt 4 ] 2 [Pt 6 (CO) 10 (dppf)]·2CH 3 CN, Pt 2 (CO) 2 (dppa) 3 ·0.5CH 3 CN, Pt 8 (CO) 6 (PPh 2 ) 2 (C≡CPPh 2 ) 2 (dppa) 2 ·2thf, and Pt(dppb) 2 were determined by single-crystal diffraction (dmf = dimethylformamide; thf = tetrahydrofuran).

The reaction of [NEt 4 ] 2 [Ni 6 (CO) 12 ] in thf with 0.5 equiv of PCl 3 affords the monophosphide [Ni 11 P(CO) 18 ] 3- that in turn further reacts with PCl 3 resulting in the tetra-phosphide carbonyl cluster [HNi 31 P 4 (CO) 39 ] 5- . Alternatively, the latter can be obtained from the reaction of [NEt 4 ] 2 [Ni 6 (CO) 12 ] in thf with 0.8-0.9 equiv of PCl 3 . The [HNi 31 P 4 (CO) 39 ] 5- penta-anion is reversibly protonated by strong acids leading to the [H 2 Ni 31 P 4 (CO) 39 ] 4- tetra-anion, whereas deprotonation affords the [Ni 31 P 4 (CO) 39 ] 6- hexa-anion. The latter is reduced with Na/naphthalene yielding the [Ni 31 P 4 (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 [Ni 11 P(CO) 18 ] 3- , [HNi 31 P 4 (CO) 39 ] 5- , and [H 2 Ni 31 P 4 (CO) 39 ] 4- . The reversible formation of the stable [Ni 11 P(CO) 18 ] 4- tetra-anion is demonstrated through the spectroelectrochemical investigation of [Ni 11 P(CO) 18 ] 3- . The redox changes of [HNi 31 P 4 (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 [HNi 31 P 4 (CO) 39 ] n- (n = 3-11) are reported. The spectroelectrochemical investigation of [H 2 Ni 31 P 4 (CO) 39 ] 4- revealed the presence of three chemically reversible reduction processes, and the IR spectra of [H 2 Ni 31 P 4 (CO) 39 ] n- (n = 4-7) have been recorded. The different spectroelectrochemical behavior of [HNi 31 P 4 (CO) 39 ] 5- and [H 2 Ni 31 P 4 (CO) 39 ] 4- support their formulations as polyhydrides. Unfortunately, all the attempts to directly confirm their poly hydrido nature by 1 H 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.

The reaction of [Rh 7 (CO) 16 ] 3- with BiCl 3 under N 2 and at room temperature results in the formation of the new heterometallic [Bi@Rh 12 (CO) 27 ] 3- cluster in high yields. Further controlled addition of BiCl 3 leads first to the formation of the dimeric [(Bi@Rh 12 (CO) 26 ) 2 Bi] 5- and the closo-[Bi@Rh 14 (CO) 27 Bi 2 ] 3- species in low yields, and finally, to the [Bi@Rh 17 (CO) 33 Bi 2 ] 4- cluster. All clusters were spectroscopically characterized by IR and electrospray ionization mass spectrometry, and their molecular structures were fully determined by X-ray diffraction studies. Notably, they represent the first examples of Bi atoms interstitially lodged in metallic cages that, in this specific case, are all based on an icosahedral geometry. Moreover, [Bi@Rh 14 (CO) 27 Bi 2 ] 3- forms an exceptional network of infinite zigzag chains in the solid state, thanks to intermolecular Bi-Bi distances.