Reactions of ruthenium and osmium cluster carbonyls with heteroatom-substituted and functionalized alkynes

The results of studies of the reactions of ruthenium and osmium cluster carbonyls with metal alkynes, silylalkynes, propargyl alcohols and their derivatives, diynes, enynes, and ferrocenylacetylene are summarized. Intramolecular rearrangements in the cluster complexes including migrations of carbonyl, hydride, and hydrocarbon ligands as well as the metal core reorganization are considered. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 1–17, January, 2000.     

Organometallic chemistry and homogeneous catalysis of Rh and Rh-Co mixed metal carbonyl clusters

The reactions of hydrosilane and/or alkyne as well as isonitriles with rhodium and rhodium cobalt mixed metal carbonyl clusters, e.g., Rh₄(CO)₁₂ and Co₂Rh₂(CO)₁₂, are studied. Novel mixed metal complexes, e.g., CoRh(CO)₅ (HCCBu ⁿ ), (R₃Si)₂Rh(CO) _n Co(CO)₄, Rh(R–NC)₄Co(CO)₄, Co₂Rh₂(CO)₁₀(HCCR), and Co₂Rh₂(CO)₉(HCCBu ⁿ ), are synthesized and identified. The catalytic activities of these rhodium and rhodium-cobalt mixed metal complexes are examined in hydrosilyation, silylformylation, and novel silylcarbocyclization reactions. Possible mechanisms for these reactions are proposed and discussed.     

Synthesis and Structure of New Cobalt–Carbonyl Complexes Containing Tellurium Atoms

Co₂(CO)₈ and Te₂O react to form the well known Co₄(CO)₁₀Te₂, Co₄(CO)₁₁Te₂ complexes and the two new cluster complexes CCo₆(CO)₁₂Te₂(1), and CCo₆(CO)₁₀Te₂(Te₃) (2). The structures of 1 and 2 were determined by X-ray analysis, together with the triphenylphosphine derivative of 1, CCo₆(CO)₁₁(PPh₃)Te₂(3), which was analyzed to clarify the disordered structure of the parent compound. Complex 1 is formed by a prismatic cluster of cobalt atoms with a carbon embedded in the cage; two tellurium atoms cap the triangular faces of the prism and each cobalt atom links two terminal carbonyl groups. The complex 2 has a similar prismatic cage CCo₆; two ₄-Te atoms cap two rectangular faces of the prism, while other two Te atoms bridge two edges of the triangular faces and are linked each other through a third Te atom. Electron counting gives for complex 2 92 electrons: the presence of two long Co–Co distances suggests that the two excess electrons are located on Co–Co antibonding orbitals. Crystal data for 1, space group C2/c, a = 12.845(2) Å, b = 13.449(2) Å, c = 13.246(2) Å, = 91.95(2)°, Z = 4, R = 0.097 for 2555 reflections; for 2, space group Pnna, a = 17.219(5) Å, b= 14.969(6) Å, c = 9.178(4) Å, Z = 4,R = 0.037 for 3103 reflections; for 3, space group P2₁/c, a = 9.288(2) Å, b = 14.920(6) Å, c = 26.300(9) Å, = 99.99(2)°, Z = 4, R = 0.037 for 4300 reflections. The vibrational analysis of the complex 1 was performed and most of the (CO), (₆C–Co), (Co–Co) and (Co–Co) modes were assigned. The (Co–Te) modes were interpreted on the basis of the intermolecular coupling, due to the close contact between neighboring clusters in one distinct direction in the crystal.     

Homogeneous catalysis by ruthenium carbonyl clusters

The historical background of and the incentive for using ruthenium carbonyl clusters as homogeneous catalysts are outlined. Keeping in view the possible solutions the uncertainties arising from declusterification and metal colloid formation are discussed. All ruthenium cluster-catalysed reactions are broadly classified as reactions with or without carbon monoxide as one of the reactants and the basic differences between such reactions are highlighted. Some of the factors of special relevance to cluster-catalysed reaction systems are mentioned. The reactions involving carbon monoxide are then discussed. These include water-gas-shift reaction, carbon monoxide hydrogenation, hydroformylation, reductive carbonylation of nitrobenzene and other carbonylation reactions. Hydrogenation, transfer hydrogenation, isomerisation and a few other reactions are then discussed. For all these reactions, special emphasis is laid on well-characterised cluster complexes that have been proposed as catalytic intermediates. Finally an attempt has been made to identify the path that future research in cluster catalysis is likely to follow.     

High nuclearity metal clusters: Miniature bulk of unusual structures and properties?

Recent developments in cluster synthesis have produced many high nuclearity metal clusters of discretesize andshape approaching that of small particles. Some of these clusters have metal arrangements resemblingfragments of metallic lattices and thus may be considered as aminiature bulk. Some are related to the quasicrystalline phase. Yet others have little or no structural features in common with that of the bulk. These metal clusters of definitivesize andshape provide an opportunity for the study of the evolution of band structure fromatomic tomolecular to thebulk. The focus of this review is on the unusual structures and properties of well-defined high nuclearity metal clusters and their possible relations or variant to the bulk state. Specifically, interesting electronic, optical, and magnetic properties of metal clusters in the quantum-size regime are described. Structural systematics of high nuclearity metal clusters, ranging from thecluster-of-clusters to thelayer-by-layer growth sequence, are discussed. It is hoped that further studies of the structures and properties of large metal cluster compounds of discretesize andshape will shed light on how, when, and why metallic or other bulk behavior begins and ends.     

Energy-dependent Electrospray Ionisation Mass Spectrometry of Carbonyl Clusters

The electrospray ionisation mass spectra (EDESI-MS) of Ru₆C(CO)₁₆(PPh₃) and Ir₄(CO)₁₁(PR₃) (PR₃=PPh₃, P(p-C₆H₄OMe)₃, P(p-C₆H₄NMe₂)₃, P(p-C₆H₄Cl)₃, P(OPh)₃, P(OMe)₃, PO₃C₅H₉) are described and the relative importance of carbonyl loss versus phosphine loss as a fragmentation pathway is assessed. Qualitatively, the phosphine ligands bind more strongly to Ir₄(CO)₁₁ clusters than to Ru₆C(CO)₁₆. The influence on the collision cell pressure on MS/MS spectra of transition metal carbonyl cluster anions is also explored showing that a greater, simultaneous, distribution of fragment ions is produced as the collision cell pressure is increased.Dedicated to Prof. Brian F. G. Johnson on the occasion of his retirement.     

Synthesis and structure of complexes formed in the reaction between dicobalt octacarbonyl and tetramethyl-biphosphine disulfide

Co₂(CO)₈ and Me₂P(S)P(S)Me₂ react to form the two cluster complexes: Co₄(CO)₉S(PMe₂)₂) (1) and Co₃(CO)₇S(SPMe₂) (2). The strucure of1 and of the disubstituted triphenyl phosphine derivative of2. Co₃(CO)₅(PPh₃)₂S (SPMe₃) (2a) were determined. Compound1 contains a quasi-planar rhomboidal Co₄ cluster formed by two Co₃ isosceles triangles sharing a Co-Co edge. One triangle is capped by a sulfur atom, the other triangle has two edge-bridging PMe₂ moieties. Electron counting gives 64 electrons corresponding to a planar system; the distribution of long Co-Co distances, in particular in the triangle bearing PMe₂ bridges, suggests that the excess electrons are located on Co-Co antibonding ortibals. Compound2a contains a Co₃S cluster with one side bridged by a SPMe₂ unit forming a four-membered Co₂SP ring. The substitution of two CO groups with two PPh₃ causes a large deformation of the cluster Co-Co bondscis to these two phosphorus atoms. Crystal data for1, space group P1,a = 9.728(2) Å,b = 10.288(2) Å,c = 11.860(3) Å, = 86.41(2)°, = 76.20(2)°, = 80.37(5)°,Z = 2, 5300 reflections,R = 0.0398; for2a, space group P1,a = 9.78(3) Å,b = 13.05(4) Å,c = 18.28(6) Å, = 93.23(3)°, = 99.17(2)°, = 97.26(6)°,Z = 2, 2976 reflections,R = 0.0579.     

X-ray and conformation analysis of the new trinuclear cluster of osmium Os3(μ,η2-OCC6H5)(η3-C3H5)(CO)9

The crystal structure of the Os₃(μ,η²-O=CC₆H₅)(η³-C₃H₅)(CO)₉ cluster synthesized by the reaction of the (μ-H)Os₃(μ-O=CC₆H₅)(CO)₁₀ complex with allylamine in chloroform was determined by X-ray analysis. Prolonged storage of the reaction mixture led to N-C bond cleavage in allylamine and η³-addition of the allyl fragment at one of the Os atoms (Os-C 2.246 ?, 2.248 ?, and 2.273 ?). The unit cell parameters of the complex are a = 9.494(1) ?, b = 10.479(1) ?, c = 12.474(2) ?, α = 84.55(1)°, β = 70.08(1)°, γ = 70.72(1)°, V = 1255.8(4), ?³, space group P , Z = 2; C₁₉H₁₀O₁₀Os₃; d _calc = 2.922 g/cm³, 3085 I _hkl > 2σ _I of 3611 collected reflections; R = 0.0252. The structure of Os₃(μ,η²-O=CC₆H₅)(η³-C₃H₅)(CO)₉ is molecular. The plane of the Os₃ triangle and the OsCOOs plane are connected according to the “butterfly” principle with an angle of 103.4° between them. The Os-Os distances in the cluster core vary from 2.836(1) ? to 2.844(1) ?; the Os-C_carb distances are 1.88(1)–1.97(1) ?; the distances to the atoms of the bridging ligands are Os-C 2.11(1) ?, Os-O 2.14(1) ?; the O-C bridging bond is 1.24(1) ?. of the Os₃(μ,η²-O=CC₆H₅)(η³-C₃H₅)(CO)₉ triosmium cluster were studied theoretically. The potential curve of the internal rotation of the allyl ligand relative to the Os(1)-C(9) bond was determined. The rotation barrier of the allyl ligand in crystal relative to the Os(1)-C(9) bond is 8.38 kJ/mol, and the rotation of the ligand is not hindered. The effects of the intra-and intermolecular interactions on the conformation state of the cluster complex are considered. Original Russian Text Copyright ? 2008 by V. A. Maksakov, N. V. Pervukhina, N. V. Podberezskaya, M. Yu. Afonin, V. A. Potemkin, and V. P. Kirin __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 49, No. 5, pp. 926–932, September–October, 2008.     

Altering Charges on Heterobimetallic Transition-Metal Carbonyl Clusters

The homoleptic group 5 carbonylates [M(CO)₆]⁻ (M=Nb, Ta) serve as ligands in carbonyl-terminated heterobimetallic Ag_mM_n clusters containing 3 to 11 metal atoms. Based on our serendipitous [Ag₆{Nb(CO)₆}₄]²⁺ ( 4 a ²⁺) precedent, we established access to such Ag_mM_n clusters of the composition [Ag_m{M(CO)₆}_n]^x (M=Nb, Ta; m=1, 2, 6; n=2, 3, 4, 5; x=1−, 1+, 2+). Salts of those molecular cluster ions were synthesized by the reaction of [NEt₄][M(CO)₆] and Ag[Al(OR^F)₄] (R^F=C(CF₃)₃) in the correct stoichiometry in 1,2,3,4-tetrafluorobenzene at −35 °C. The solid-state structures were determined by single-crystal X-ray diffraction methods and, owing to the thermal instability of the clusters, a limited scope of spectroscopic methods. In addition, DFT-based AIM calculations were performed to provide an understanding of the bonding within these clusters. Apparently, the clusters 3 ⁺ (m=6, n=5) and 4 ²⁺ (m=6, n=4) are superatom complexes with trigonal-prismatic or octahedral Ag₆ superatom cores. The [M(CO)₆]⁻ ions then bind through three CO units as tridentate chelate ligands to the superatom core, giving overall structures related to tetrahedral AX₄ ( 4 ²⁺) or trigonal bipyramidal AX₅ molecules ( 3 ⁺).     

Reactions of palladium(I) carbonylacetate cluster with alcohols

Reactions of a tetranuclear palladium cluster [Pd(CO)(OAc)[4 with C₁-C₃ alcohols have been found to proceed simultaneously via several routes to form CO, and dialkyl carbonates, the products of oxidation of coordinated CO ligands, along with carbonyl compounds which form due to oxidation of the corresponding alcohols. Alkoxy, alkoxycarbonyl, and acyl palladium derivatives are shown to be the intermediates of the reactions studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2456–2459, October, 1996.     

Preparation and reactivity of metal-containing monomers

Mono- and disubstituted cluster metal-containing monomers were obtained under mild conditions on interaction of Rh₆(CO)₁₆ with 4-vinylpyridine (4-ViPy) in the presence of N-trimethylaminoxide. These products were characterized by IR and¹H NMR spectroscopy and by elemental and X-ray analyses. Rh₆(CO)₁₅(4-ViPy) was found to be an octahedral cluster with eleven terminal and four ₃-bridging carbonyl ligands. 4-ViPy is linked with the Rh(3) atom through the N atom and occupies the coordination site of the twelfth CO terminal ligand. The mean value of the Rh-Rh bond length is 2.762 Å. The unsaturated ligand has little or no effect on the geometry of the starting cluster and its double bond retains the ability to undergo addition reactions.For part 28, seeRuss. Chem. Bull., 1993, 453.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 975–979, May, 1993.     

Synthesis and Isolation of Titanium Metal Cluster Complexes and Ligand-Coated Nanoparticles with a Laser Vaporization Flowtube Reactor

A new laser vaporization flow reactor (LVFR) is described consisting of a laser ablation cluster source combined with a fast flowtube reactor for the production and isolation of ligand-coated metal clusters. The source includes high repetition rate laser vaporization with a 100 Hz KrF (248 nm) excimer laser, while cluster growth and passivation with ligands takes place in a flowtube with ligand addition via a nebulizer spray. Samples are isolated in a low temperature trap and solutions containing the clusters are analyzed with laser desorption time-of-flight mass spectrometry. Initial experiments with this apparatus have trapped Ti _x (ethylenediamine) _y complexes which apparently have linear metal units with octahedral ligand coordination. Other experiments have produced and isolated clusters of the form Ti _x O _y (THF) _z that apparently have linear metal oxide cores and larger (TiO₂) _x (THF) _y nanoparticle species. The isolation of these new cluster species suggest that the LVFR instrument has considerable potential for the production of new nanocluster materials.     

Metallation of the methyl group ino-nitrosotoluene: synthesis and the molecular structure of the binuclear complex [o-(NO)(CH2)C6H4)]2Pd2(μ-OOCCF3)2

The reaction of the tetranuclear cluster Pd₄(CO)₄(OOCCF₃)₄ witho-nitrosotoluene afforded the Pd¹¹-containing complex [o-(NO)(CH₂)C₆H₄]₂Pd₂(μ-OOCCF₃)₂. The elimination of CO₂ and the formation of organic products of transformation of tolylnitrene species (azotoluene, ditolylamine, and tolylisocyanate) were observed in the course of the reaction. The title complex was characterized by IR and¹H NMR spectroscopy. Its structure was established by X-ray diffraction analysis. It was suggested that the reaction proceeds through intermediate formation of nitrene complexes. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 147–150, January, 2000.     

Hexa- and triosmium carbonyl clusters bearing bridging dppm and capping sulfido ligands

Treatment of [Os₃(CO)₇(μ₃-S)₂(μ-dppm)] (1) with Me₃NO in toluene at 80 °C affords the trinuclear cluster [Os₃(CO)₆(μ₃-S)₂(NMe₃)(μ-dppm)] (2) and the hexanuclear cluster [Os₆(CO)₁₂(μ₃-S)₄(μ-dppm)₂] (3) in 30% and 51% yields, respectively. The reaction of 1 with [Os₃(CO)₁₀(MeCN)₂] in refluxing benzene at 80 °C gives the hexanuclear cluster [Os₆(CO)₁₄(μ₃-S)₂(μ-dppm)] (4) in 15% yield. Compound 2 reacts with CO, PPh₃ and P(OMe)₃ at room temperature to give 1, [Os₃(CO)₆(μ₃-S)₂(μ-dppm)(PPh₃)] (5) and [Os₃(CO)₆(μ₃-S)₂(μ-dppm){P(OMe)₃}] (6), respectively; in high yields indicating that the NMe₃ ligand is weakly bound. Compound 1 reacts with PPh₃ in presence of Me₃NO to afford 5, 2 and 3 in 53%, 6% and 18% yields, respectively, whereas with P(OMe)₃1 gives only 6 in 84% yield. Compound 3 reacts with CO at 98 °C to regenerate 1 by the cleavage of the three unsupported osmium-osmium bonds. The molecular structures of 4 and 6 have been unambiguously determined by single crystal X-ray diffraction studies. The hexanuclear compound 3 appears to be a64-electron butterfly core with four triply bridging sulfido ligands and two bridging dppm ligands based on the spectroscopic and analytical data. The metal core of 4 can be described as a central tetrahedral array capped on two faces with two additional osmium atoms. The triply bridging sulfido ligands face cap the two tetrahedral arrays formed by metal capping of the two faces of the central tetrahedron. The dppm ligand bridges one edge of one of the external tetrahedral arrays. Compounds 5 and 6 are formed by the displacement of equatorial carbonyl group of 1 by a PPh₃ and P(OMe)₃ ligand respectively and their structures are comparable to that of 1.     

Pyridine adsorption on small Nin‐cluster (n = 2,3,4): A study of geometry and electronic structure

Adsorption of pyridine on Ni_n‐clusters (with n = 2,3,4) is studied by quantum chemical calculations at B3LYP/LANL2DZ and B3LYP/6‐311G^** levels. First, Ni_n‐clusters are investigated for accessible structure and electronic states. The lowest electronic state with four unpaired electrons is predicted for Ni₄‐cluster based on geometry and electronic structure, showing that the cluster stability nicely depends on number of unpaired electrons. Correction for basis set superposition error of metal‐metal bond is appreciable and has increasing effect on cluster binding energy. Next, adsorption of pyridine in planar and vertical adsorption modes is investigated on rhombus Ni₄‐cluster. The vertical mode is found (at B3LYP/6‐311G^** level) as the most favorable adsorption mode. Adsorption energy (ΔE_ads) depends on cluster size; adsorption on Ni₄‐cluster is most favorable with ΔE_ads = ?207.33 kJ/mol. The natural bond orbital analysis reveals the charge transfer in adsorbate/metal‐cluster. Results of investigations for the Ni₂‐ and Ni₃‐cluster are also presented. © 2012 Wiley Periodicals, Inc.     

Significant nonlinear‐optical switching capacity in atomic clusters built from silicon and lithium: A combined ab initio and density functional study

Starting from a hypothetical but fundamental charge/discharge sequence, the topic of nonlinear optical switching in atomic clusters built from silicon and alkali metals is opened up. The outcomes presented in this work, obtained with ab initio methods of exceptional predictive capabilities, offer strong evidences that sizable hyperpolarizability contrasts between neutral and charged alkali metal doped cluster forms might be simultaneously accomplished. The observed switching procedure involves redox polyatomic clusters formed by Si atoms. These centers function as electron acceptors at the ground state and as electron donors at the excited states facilitating low energy charge transfer transitions upon electronic excitation. © 2014 Wiley Periodicals, Inc.     

Surface Mediated Organometallic Synthesis: Formation of [H5Os10(CO)24]− by Hydrogenation of Silica-Supported [Os(CO)3(OH)2]n as a Springboard for a High-Yield Synthesis of [H4Os10(CO)24]2− Starting from α-[Os(CO)3Cl2]2 and Working in Ethylene Glycol Solution

New high yield routes to the high nuclearity hydrido carbonyl clusters [H₅Os₁₀(CO)₂₄]^- and [H₄Os₁₀(CO)₂₄]^2-, model systems for the chemisorption of CO and H₂ on metal surfaces, are reported. [H₅Os₁₀(CO)₂₄]^- is obtained in good yields by hydrogenation (1 atm) at 200°C of physisorbed [Os(CO)₃(OH)₂]_n whereas in refluxing ethylene glycol solution, that is less acidic than the silica surface, [H₄Os₁₀(CO)₂₄]^2- is obtained in high yield starting from [Os(CO)₃(OH)₂]_n or, more conveniently, from -[Os(CO)₃Cl₂]₂ in the presence of the stoichiometric amount of sodium carbonate. The quantitative equilibrium

Investigations into cluster formation with alkyl-tethered bis-calix[4]arenes

Abstract

Calix[4]arenes are versatile ligands capable of forming a wide range of cluster motifs when reacted with 3d, 4f or 3d/4f metal ions. Synthetic modification at the calix[4]arene methylene bridge offers a unique opportunity to explore cluster formation with these alternative building blocks. Here, we present the synthesis of a range of bis-calix[4]arenes that are tethered by alkyl chains, as well as exploratory structural studies into cluster-forming reactions. Single crystals were formed in four cases, and from the X-ray structures elucidated it is possible to conclude that sufficiently long alkyl tethers allow for the formation of established cluster topologies without disruption to the core coordination chemistry.