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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 and31P 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)2were determined by single-crystal diffraction (dmf = dimethylformamide; thf = tetrahydrofuran).

The reaction of the [Rh-7(CO)(16)](3-) cluster anion with Ge2+ salts, in different stoichiometric ratios and under different atmospheres, leads to the formation of new heterometallic Rh-Ge clusters, representing the first known examples of Rh carbonyl compounds containing interstitial germanium atoms. More specifically, under N-2 the reaction progressively affords the new [Rh13Ge(CO)(25)](3-) and [Rh14Ge2(CO)(30)](2-) clusters in good yields, with the Ge atoms located in cubic and square-anti-prismatic cavities, respectively. However, under a CO atmosphere, the [Rh13Ge(CO)(25)](3-) derivative undergoes a significant structural and chemical rearrangement giving the new compound, [Rh12Ge(CO)(27)](4-), where Ge is hosted in an icosahedral metal cage. All species have been characterized by IR spectroscopy and ESI mass spectrometry, and their structures have been elucidated by single-crystal X-ray diffraction. Additionally, preliminary biological tests on the [Rh13Ge(CO)(25)](3-) and [Rh14Ge2(CO)(30)](2-) clusters show that they are cytotoxic to various cell lines.

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.

The reaction of [Rh7(CO)16]3- with BiCl3 under N2 and at room temperature results in the formation of the new heterometallic [Bi@Rh12(CO)27]3- cluster in high yields. Further controlled addition of BiCl3 leads first to the formation of the dimeric [(Bi@Rh12(CO)26)2Bi]5- and the closo-[Bi@Rh14(CO)27Bi2]3- species in low yields, and finally, to the [Bi@Rh17(CO)33Bi2]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@Rh14(CO)27Bi2]3- forms an exceptional network of infinite zigzag chains in the solid state, thanks to intermolecular Bi-Bi distances.

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.

The reaction of [Pt12(CO)24]2– with CH2═C(PPh2)2 (PP) results in the neutral tetrahedral cluster Pt4(CO)4(PP)2. This reacts with strong acids such as HBF4 to afford, first, the [HPt4(CO)4(PP)2]+ monohydride monocation and, then, the [H2Pt4(CO)4(PP)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(PP)2 and [H2Pt4(CO)4(PP)2]2+ are static in solution, whereas [HPt4(CO)4(PP)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(PP)2 core to which the hydride ligands are added stepwise.

N-Heterocyclic Carbene Rhodium Complexes: Conformational Analysis and Catalytic Studies G. Solinasa, M. A. Bruckaa, M. C. Cassania, C. Femonia, R. Mazzonia, M. Mancinellib, A. Mazzantib aDipartimento di Chimica Fisica ed Inorganica, Università di Bologna, viale Risorgimento, 4, Bologna bDipartimento di Chimica Organica “A. Mangini”, Università di Bologna, viale Risorgimento, 4 Bologna gavino.solinas2@unibo.it N-Heterocyclic carbenes (NHCs) have attracted considerable attention as a new class of ligands over the past decade1 and recently our research in this field has been dealing with the syntheses of rhodium(I) complexes presenting axial chirality and catalitically active in the hydrosilylation of terminal alkynes and in the addition of arylaldehydes with phenylboronic acid.2 We now present the synthesis, characterization (X-ray, VT NMR, DFT calculation) and catalysis of the new NHC-Rh(I) complexes shown below. Preliminary studies on NHC-Fe(II) complexes will be also presented and discussed. References 1. Mercs, L.; Albrecht, M. Chem. Soc. Rev. 2010, 39, 1903. (b) Diez-Gonzalez, S.; Marion, N.; Nolan, S. P. Chem. Rev. 2009, 109, 3612. 2, Busetto L.; Cassani, M.C.; Femoni, C.; Mancinelli, M.; Mazzanti, A.; Mazzoni, R.; Solinas, G. Organometallics 2011, 30, 5258.

The reaction of [Ni10C2(CO)16]2− with Co3(μ3-CCl)(CO)9 results in the new bimetallic Ni−Co hexacarbido carbonyl clusters [H6−nNi22Co6C6(CO)36]n− (n = 3−6), which possess polyhydride nature and can be interconverted by means of acid−base reactions. The tetra-anion [H2Ni22Co6C6(CO)36]4− and the hexa-anion [Ni22Co6C6(CO)36]6− have been isolated in a crystalline state and structurally characterized via X-ray crystallography. The six carbide atoms are lodged into Ni7CoC square antiprismatic cages. Addition of strong bases to [Ni22Co6C6(CO)36]6− affords mixtures of the monoacetylides [Ni9CoC2(CO)16]3− and [Ni9CoC2(CO)15]3−, which have been cocrystallized as [NEt4]3[Ni9CoC2(CO)16−x] (x = 0.58−0.84) salts, displaying tightly bonded interstitial C2 units.

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 Xray 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.

The previously ill-characterized [HxRh22(CO)(35)](4-/5-) carbonyl cluster has been obtained as a byproduct of the synthesis of [H3Rh13(CO)(24)](2-) and effectively separated by metathesis of their sodium salts with [NEt4]Cl. Although the yields are modest and never exceed 10-15% (based on Rh), this procedure affords spectroscopically pure [H3Rh22(CO)(35)](5-) anion. Formation of the latter in mixture with other Rh clusters was also observed by electrospray ionization-mass spectrometry (EST-MS) in the oxidation of [H2Rh13-(CO)(24)](3-) with Cu2+ salts. The recovery of further amounts of [H3Rh22(CO)(35)](5-) was hampered by too similar solubility of the salts composing the mixture. Conversely, the reaction in CH3CN of [H2Rh13(CO)(24)](3-) with [Cu(MeCN)(4)](+)[BF4](-) leads to the [H2Rh13(CO)(24){Cu(MeCN)}(2)](-) bimetallic cluster. The X-ray crystal structures of [H4Rh22(CO)(35)](4-), [H3Rh22(CO)(35)](5-), and [H2Rh13(CO)(24){Cu(MeCN)}(2)](-) are reported. From a formal point of view, the metal frame of the former two species can be derived by interpenetration along two orthogonal axes of two moieties displaying the structure of the latter. The availability of [H8-nRh22(CO)(35)](n-) salts prompted their detailed chemical, spectroscopic, and electrochemical characterization. The presence of hydride atoms has been directly proved both by ESI-MS and H-1 NMR Moreover, both [H4Rh22(CO)(35)](4-) and [H3Rh22(CO)(35)](5-) undergo distinctive electrochemically reversible redox changes. This allows to assess electrochemical studies as indisputable though circumstantial evidence of the presence of H-1 NMR-silent hydride atoms in isostructural anions of different charge.

The new [Pt-13(CO)(12){Cd-5(mu-Br)(5)Br-2(dmf)(3)}(2)](2-) and [Pt-19(CO)(17){Cd-5(mu-Br)(5)Br-3(Me2CO2)}{Cd-5(mu-Br)(5)Br(Me2CO)(4)}](2-) clusters have been obtained in good yields by reaction of [Pt-12(CO)(24)](2-) with CdBr2 center dot H2O in dmf at 90 degrees C and structurally characterized by X-ray diffraction. Their structures consist of a Pt-centered Pt-13(CO)(12) icosahedron and a Pt-19(CO)(17) interpenetrated double icosahedron, respectively, decorated by two Cd-5(mu-Br)(5)Br5-x(solvent)(x) rings. Their surface decoration may be related to that of Au-Fe-CO clusters as well as to the staple motifs stabilizing gold-thiolates nanoclusters. An oversimplified and unifying approach to interpret their electron count is suggested.

The di-hydride di-anion [H2Fe4(CO)(12)](2-) has been quantitatively obtained by protonation of the previously reported mono-hydride tri-anion [HFe4(CO)(12)](3-) in DMSO and structurally characterised in its [NEt4](2)[H2Fe4(CO)(12)] salt. It shows some subtle but yet significant differences in the stereochemistry of the ligands in comparison to the heavier Ru-4 and Os-4 congeners. The study of the reactivity of these [H4-nFe4(CO)(12)](n-) (n = 2,3) species allowed the serendipitous isolation and structural characterization of the new pentanuclear [HFe5(CO)(14)](3-) mono-hydride tri-anion. Attempts to obtain the latter in better yields led to the discovery of intermolecular CO/H- mutual exchange reactions and isolation and structural characterization of the [Fe(DMF)(4)][Fe-4(CO)(12)(mu(5)-eta(2)-CO)(mu-H)](2)center dot 0.5CH(2)Cl(2) and [M+][Fe-4(CO)(12)(mu(4)-eta(2)-CO)(mu-H)](-) (M = K, Cs) adducts, the former containing an unprecedented isocarbonyl group. The isolation of new tetranuclear and, above all, pentanuclear hydridocarbonylferrates indicates that it is possible to further expand the chemistry of homoleptic Fe carbonyl species

Imidazolium salts incorporating functional groups represent a class of compounds having great versatility due to their wide range of applications as task specific ionic liquids (ILs)1 or N-heterocyclic carbene precursors (NHCs)2. Recently our research in this field has been dealing with the high-purity synthesis of t-butyloxylcarbonyl (Boc)-protected and deprotected amino-functionalized imidazolium cation [NHR1CH2CH2ImR2]+ ([1]+, R1 = Boc, H; R2 = Me, Bz, Allyl) and related NHC-Ag(I) silver complexes have been obtained by reacting [1]+ with Ag2O.3 Here we report the synthesis of new NHC-Rh(I) (2) complexes that contain an axis of chirality. The enantiomerical inversion has been investigated by variable-temperature NMR spectroscopy, DFT calculation and X-ray diffraction. The catalytic behaviour of 2 in the 1,2 addition reaction of aryl aldehydes with boronic acid will be also presented and discussed.

We have recently described the synthesis and characterization of amino-functionalized N-heterocyclic carbene complexes of silver(I), Ag(I)-NHCs, using the Boc-protected and deprotected 1-(2-aminoethyl)-3-methyl imidazolium salts [NH2(CH2)2ImMe]X, [1]X (X = I, PF6) as carbene precursors [1]. We are now presenting the preparation of a new gold(III)-alkylamino imidazolium aurate salt [Cl3AuNH2(CH2)2ImMe)][AuCl4] (2). Demonstrating the great versatility of the amino-functionalized imidazolium salts, such compound is an useful precursor for the preparation of gold nanoparticle (AuNPs) films via the layer-by-layer (LBL) assembly method [2]. Assembling appropriate polyelectrolytes such as poly(ethyleneimine) (PEI) on Indium Tin Oxide Glasses (ITO) a monolayer film of 2 can be easily grafted on the surface and after subsequent reduction, well controlled, in size and distribution, immobilized AuNPs can be generated. The morphology of the AuNPs layers was investigated by using AFM and SEM microscopy and X-ray diffraction (XRD). References [1] L. Busetto, M.C. Cassani, C. Femoni, A. Macchioni, R. Mazzoni, D. Zuccaccia, J. Organomet. Chem. 693, 2579 (2008). [2] J.F. Quinn, A.P.R. Johnston, G.K. Such, A.N. Zelikin, F. Caruso, Chem. Soc. Rev. 36, 707 (2007).