Organometallic Clusters Research Articles

Facile assembly of a Cu9 amido complex: a new tripodal ligand design that promotes transition metal cluster formation

A tripodal amido ligand with a central non-chelating phosphorus donor allows for the facile assembly of a pentane soluble organometallic copper cluster with a central copper atom surrounded by a nonplanar chain of eight copper atoms and two terminal amido-copper bonds.

First mixed hydrazide/hydroxylamide metal aggregates

The first organometallic clusters of mixed hydrazide/hydroxylamide clusters of zinc, [Zn(MeZn)(4)(HNNMe(2))(2)(ONEt(2))(4)] and {Zn(EtZn)(4)[HNN(CH(2))(5)](2)(ONEt(2))(4)} were synthesized in one-pot synthesis protocols from dialkylzinc solutions, substituted hydrazines and N,N-diethylhydroxylamine; competing for the Zn atoms, the different binding properties of hydrazide and hydroxylamide ligands in these heteroleptic clusters are discussed.

Organometallic cluster analogues of tamoxifen: Synthesis and biochemical assay

Simple organometallic cluster analogues of tamoxifen containing triosmium or dicobalt carbonyl fragments have been prepared. Attempts at elaboration of these towards the tamoxifen skeleton were hampered by sensitivity of the cluster–ligand linkage towards the McMurry coupling conditions. Preliminary biological tests on various substrates indicate that the transition metal carbonyl fragment increases lipophilicity dramatically and reduces affinity for the estrogen receptor.

ToF-SIMS analysis of surface-anchored organometallic clusters

ToF-SIMS analysis of the organometallic cluster Os 3(μ-H)(CO) 10(μ-SCH 2CH 2SH) chemically attached onto a silver or gold surface, and of the cluster fragment Os 3(μ-H)(CO) 10(μ-OSi ) on a silica surface, allows for identification of the surface organometallic species, and also gives information on its reactivity.

Investigations on Butterfly Fe/S Cluster S‐Centered Anions (μ‐S‐)2Fe2(CO)6, (μ‐S‐)(μ‐RS)Fe2(CO)6, and Related Species

AbstractFor Abstract see ChemInform Abstract in Full Text.

Eight-Vertex Tetrametallic Structures Derived from Cubanes: A Close Relationship between Bisdisphenoidal Metallaborane and Organometallic Clusters

The metallaborane Cp4Co4B4H4 and the organometallic cluster Cp4Fe4C4H4 (Cp = eta5-cyclopentadienyl) not only are isoelectronic but also exhibit completely analogous eight-vertex bisdisphenoidal structures. Such structures, as well as the tetracapped tetrahedral structure of the Cp4Fe4(mu3-CO)4 precursor to Cp4Fe4C4H4, can be derived from a cube by insertion of diagonals in each of the six faces. Furthermore, the formation of Cp4Fe4C4H4 from Cp4Fe4(mu3-CO)4 can be described as a double diamond-square-diamond process preserving D2d symmetry throughout the process.

Synthesis and structure of the organometallic MFe2(µ3-S)2clusters (M = Mo or Fe)

New organometallic clusters with the MFe2(mu3-S)2 core (M = Mo or Fe) have been synthesized from inorganic [MoFe3S4] or [Fe4S4] clusters under high pressure CO. The reaction of (Cl4-cat)2Mo2Fe6S8(PR3)6[R = Et, (n)Pr] with high pressure CO produced the crystalline [MoFe2S2]4+ clusters, (Cl4-cat)Mo(O)Fe2S2(CO)(n)(PR3)6-n[n= 4, Et =I, (n)Pr =II; n = 5, Et =III] after flash column chromatography. The similar [MoFe2S2]4+ cluster, (Cl4-cat)2MoFe2S2(CO)2(depe)(2)(IV), also has been achieved by the reactions of (Cl4-cat)MoFe3S3(CO)6(PEt3)2 with depe by reductive decoupling of the cluster. For the [Fe3(mu3-S)2]4+ cluster, [Fe4S4(PcHex3)4](BPh4) was reacted with high pressure CO to produce a new Fe3S2(CO)7(PcHex)(2)(V) compound. These reactions generalized the preparation of organometallic compounds from inorganic clusters. All the compounds have been characterized by single crystal X-ray crystallography. A possible reaction pathway for the synthesis of the MFe2(mu3-S) clusters (M = Mo or Fe) has also been suggested.

Investigations on Butterfly Fe/S Cluster S-Centered Anions (μ-S-)2Fe2(CO)6, (μ-S-)(μ-RS)Fe2(CO)6, and Related Species

This Account describes the formation and chemical reactivities of the novel butterfly Fe/S cluster anions (mu-S(-))(2)Fe(2)(CO)(6) (I), (mu-S(-))(mu-RS)Fe(2)(CO)(6) (II), (mu-S(-))(mu-RS)[Fe(2)(CO)(6)](2)(mu(4)-S) (III), (mu-S(-))(mu-RS)[Fe(2)(CO)(6)](3)(mu(4)-S)(2) (IV), and {(mu-S(-))(mu(4)-S)[Fe(2)(CO)(6)](2)}(2)(mu-SZS-mu) (V). It also gives a description of the novel structures, unique properties, and wide applications of the corresponding butterfly Fe/S cluster complexes produced from these anions. Anions I-V along with their products are important in the development of organometallic chemistry, cluster chemistry, catalysis, and material and life sciences.

“Inorganic and Organometallic Clusters and Polymers: Syntheses and Applications” Symposium

AbstractConference Reports: This section contains reports on topical conferences. Reports are usually written at the request of the editorial office, but unsolicited contributions are also welcome. Suggestions should be sent to the editorial office of the Macromolecular journals, preferably by E‐mail to macromol@wiley‐vch.de.

Iron wheels on silicon: wetting behavior and electronic structure of adsorbed organostannoxane clusters.

Atomic force microscopy and synchrotron radiation (SR) spectroscopy have been used to study the wetting behavior and electronic structure of thin films of a novel organometallic cluster--[BuSn(O)OC(O)Fc]6 ("Fc" = ferrocenyl)--on silicon substrates. This cluster comprises six ferrocene units connected to a stannoxane central core--"an iron wheel on a tin drum" (V. Chandrasekhar; et al. Angew. Chem., Int. Ed. 2000, 39, 1833). Thin films spin-cast onto native oxide-terminated silicon readily dewet the substrate. We have utilized advanced image analysis techniques based on Minkowski functionals to provide a detailed quantitative analysis of the morphology of the stannoxane overlayers. This analysis shows that the dewetting patterns are rather far removed from those expected to arise from a simple Poisson distribution of centers, and we discuss the implications of this finding in terms of nucleated and spinodal dewetting. Variations in both the surface roughness and the in-plane correlation length have been followed as a function of annealing time to probe the surface dewetting dynamics. SR valence band photoemission illustrates that the highest occupied molecular orbital (HOMO) of the cluster is found 2 eV below the Fermi level. Fe 2p --> 3d and Sn 3d --> 5p resonant photoemission spectroscopy have been used to enhance the cross sections of the partial density of states associated with the Fe and Sn atoms. Sn atoms make a large contribution to the HOMO of the cluster, whereas the Fe atoms are associated with an electronic environment seemingly very similar to that in the "parent" ferrocene molecule.

An evaluation by density functional theory of M-M interactions in organometallic clusters with the [Fe(3)MoS(3)](2+) cores.

Density functional theory calculations were carried out on the structurally characterized [(Cl(4)-cat)Mo(py)Fe(3)S(3) (CO)(4)(P(n)Pr(3))(3)], A, and (Cl(4)-cat)Mo(py)Fe(3)S(3)(CO)(6)(PEt(3))(2), B, and also on A(2)(-) and B(2+) clusters. The Fe-Fe distances in these molecules depend on the total number of valence electrons (60 e(-) in A and B(2)(+) and 62 e(-) in A(2)(-) and B) and undergo great structural changes upon addition or removal of electrons. The changes are consistent with known electron-counting rules in organometallic chemistry. The weak nature of the Fe-Fe bonding interactions in these clusters is apparent in the very similar energies of states with widely different Fe-Fe distances.

A Novel Network Structure of Organometallic Clusters in Gas Phase

AbstractFor Abstract see ChemInform Abstract in Full Text.

Optical limiting properties of two organometallic half-open cubane-like cluster compounds [( η5-C 5Me 5)WS 3Cu 3Br 2(EPh 3) 2] (E=As,P)

Reactions of [PPh 4][( η 5-C 5Me 5)WS 3] with CuBr and EPh 3 (E=As,P) in MeCN gave rise to [( η 5-C 5Me 5)WS 3Cu 3Br 2(EPh 3) 2] ( 1: E=As; 2: E=P) in high yield. Single-crystal X-ray analysis revealed that the structure of 1 or 2 consists of a half-open cubane-like [WS 3Cu 3Br] cluster core where one Cu–Br bond is broken. The optical limiting properties for 1 and 2 in CH 2Cl 2 were studied with 12 ns and 35 ps laser pulses at 532 nm. The linear transmittance and thresholds at 532 nm laser light for 1 and 2 are 58% and 2.1 J cm −2, and 41% and 1.9 J cm −2, respectively. The optical limiting properties of 1 and 2 are compared with those of known closed cubane-like and nest-like clusters derived from [MS 4] 2−, [MOS 3] 2− (M=Mo,W), and [MoSe 4] 2− anions.

Nitric Oxide Reduction by Carbon Monoxide over Supported Hexaruthenium Cluster Catalysts. 1. The Active Site Structure That Depends on Supporting Metal Oxide and Catalytic Reaction Conditions.

Ruthenium site structures supported on metal oxide surfaces were designed by reacting organometallic Ru cluster [Ru6C(CO)16](2-) or [Ru6(CO)18](2-) with various metal oxides, TiO2, Al2O3, MgO, and SiO2. The surface Ru site structure, formed under various catalyst preparation and reaction conditions, was investigated by the Ru K-edge extended X-ray absorption fine structure (EXAFS). Samples of [Ru6C(CO)16](2-)/TiO2(anatase) and [Ru6C(CO)16](2-)/TiO2(rutile) were found to retain the original Ru6C framework when heated in the presence of NO (2.0 kPa) or NO (2.0 kPa) + CO (2.0 kPa) at 423 K, i.e., catalytic reaction conditions for NO decomposition. At 523 K, the Ru-Ru bonds of the Ru6C framework were cleaved by the attack of NO. In contrast, the Ru site became spontaneously dispersed over TiO2 (anatase). When being supported over TiO2 (mesoporous), MgO, or Al2O3, the Ru6C framework split into fragments in gaseous NO or NO + CO even at 423 K. The Ru6 framework of [Ru6(CO)18](2-) was found to break easily into smaller ensembles in the presence of NO and/or CO at 423 K on support. Taking into consideration the realistic environments in which these catalysts will be used, we also examined the effect of water and oxygen. When water was introduced to the sample [Ru6C(CO)16](2-)/TiO2(anatase) at 423 K, it did not have any effects on the stabilized Ru6C framework structure. In the presence of oxygen gas, however, the Ru hexanuclear structure decomposed into isolated Ru cations bound to surface oxygen atoms of TiO2 (anatase).

Condensed polyhedral boranes and analogous organometallic clusters: a molecular orbital and density functional theory study on the cap–cap interactions

AbstractThe interactions between the non‐bonded atoms on adjacent units were assumed to be one of the major factors that hinder the exploration and advancement of macropolyhedral borane chemistry. In sandwich complexes involving boron as the bridging atom, the interaction between non‐bonded atoms tends to be antibonding, but a closer analysis of various condensed systems shows that this cannot be generalized. The overlap populations (OPs) calculated for structures optimized at the B3LYP/6‐31g* level [B21H181− (5), B20H16 (6), [Al(C2B4H6)2]1− (7), B12H102− (8), B10H82− (9 and 14), B11H13 (10), B10H14 (11), C2B8H12 (13) and B20H182− (15)] indicate bonding interactions between the caps, except for 7 and 13. This is substantiated by a detailed extended Hückel‐based molecular orbital (MO) study using B10H14 as a model system to represent macropolyhedral boranes with higher fusions. An isolobal equivalent structure, [C8H6(Ru(CO)2Me)2] (17), studied at the B3LYP/LANL2DZ level has weak RuRu interactions. An analysis of the nature of the MOs in B10H14 (11) shows that there is no direct head on overlap of the cap orbitals that are antibonding; this is in contradiction to sandwiched molecules (7), where there are two occupied MOs with antibonding interactions. The m + n + o electron pair count (m is the number of cages involved in condensation, n is the number of vertices and o is the number of single vertex condensations) of sandwich complexes requires the filling of these two MOs. The negative OP between the carbon atoms in 13 is attributed to the greater electronegativity of carbon and is substantiated by a fragment MO analysis. Copyright © 2003 John Wiley & Sons, Ltd.

The active site and catalytic mechanism of NiFe hydrogenases

This Perspective describes, from our own personal experiences, how the architecture of the NiFe hydrogenase active site has been elucidated by a combination of protein crystallography, Electron paramagnetic resonance and Fourier transform infrared spectroscopic studies. Thus within a period of eight years our perception of the active center has changed from a mononuclear Ni center with S and N/O coordination to a binuclear NiFe unit with thiolate (to Ni and Fe) and CO and CN− (to Fe) ligands. This biologically unusual organometallic cluster poses a real challenge in terms of understanding the role of its different components. Current ideas concerning the NiFe hydrogenase catalytic mechanism are discussed in this context.

Magnetism and energetics of the 4d bimetallic cluster Pd6Ru6

AbstractA density functional investigation into the energetics and magnetism of a novel 4d transition metal cluster possessing an equal number of “open‐shell” Ru atoms and “closed‐shell” Pd atoms is presented. The two atom types give rise to a potentially rich spectrum of low‐energy geometric cluster structures and corresponding cluster wavefunctions. The cluster's structure is based on experimental data for a denuded highly symmetric (D3d) organometallic cluster and then optimized, allowing for energy‐lowering structural symmetry breaking, to a C2h configuration. The cluster wavefunction is then is calculated for high and low multiplicities with and without employing the natural structural symmetry of the cluster. Of particular interest is the magnetism of the cluster and the extent of 4d spin polarization of the Pd atoms by the Ru atoms in the cluster. We find that the energetically favored state of the cluster has high multiplicity with significant spin density carried by the Pd atoms. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2003

Organophosphazenes. 25. The synthesis and electrochemistry of the dicobalt hexacarbonyl complexes of phenylethynylcyclophosphazenes

The syntheses of the dicobalt hexacarbonyl complexes, N3P3F6-n(C[Formula: see text]CPhCo2(CO)6)n (n = 1 (3), n = 2 (4)), is reported. The introduction of the organometallic fragment allows for simplification of the NMR spectra and separation of the isomers of the disubstituted (4) derivatives. Electrochemical studies show that 3 undergoes a reversible one-electron reduction. At 233 K, the geminal isomer of 4 undergoes two separate reversible one-electron reductions. The ESR spectra of the radical anions of 3 and 4 have been obtained and show the absence of delocalization of unpaired spin density from the organometallic cluster to the phosphazene.Key words: cyclophosphazenes, cobalt–alkyne clusters, electrochemistry, ESR.

Electronic structure studies of Ni( [formula omitted]) surface reconstructions resulting from carbon, nitrogen, or oxygen atom adsorption

Solid-state Fenske–Hall band structure calculations have been used to study the different surface structures which result from adsorption of a half monolayer of C, N, or O atoms on the Ni(1 0 0) surface. C or N atoms sit nearly coplanar with the surface Ni atoms and induce the “clock” reconstruction of the surface. In contrast, adsorbed O atoms sit slightly above the Ni(1 0 0) surface plane and have little effect on the overall surface structure. The local environments of the C, N, and O atoms on these surfaces are similar to their environments in a series of late transition metal carbonyl clusters, suggesting that some of the same electronic factors may play a role in favoring the different structures. Results of the calculations indicate that when adsorbates occupy coplanar sites on Ni(1 0 0), much of the Ni–Ni bonding within the surface layer and between the surface- and second-layers is disrupted. On the C- and N-covered surfaces the disruption is more than compensated for by the formation of strong adsorbate-Ni bonds and by new Ni–Ni surface bonds resulting from the clock reconstruction. When O is forced into a coplanar site, however, both the higher electron count and increased electronegativity of the O atoms lead to severe disruption of the surface bonding and weak Ni–O bonds. When O atoms sit above the surface, they form more polar Ni–O bonds, contribute less electron density to the Ni surface bands, and cause less disruption to Ni–Ni surface bonds. These results suggest that, similar to the organometallic clusters, the site preferences of C, N, and O atoms are directly related to their electron count, and in turn to the relative occupation of both Ni–Ni and X–Ni (X=C, N, O) antibonding bands.

Review: Synthesis of organometallics and catalytic hydrogenations in ionic liquids

AbstractNew solvents provide synthetic chemists with the opportunity of conducting new reactions and carrying out new processes. In this paper the author's own work on organometallic chemistry in ionic liquids is reviewed and placed in context with studies from other groups in this area. Specifically, the paper will describe the use of ionic liquids in the synthesis of organometallic complexes and clusters and the use of ionic liquids in hydrogenation catalysis. The synthesis and reactivity of ionic liquids with organometallic anions will also be discussed. Copyright © 2002 John Wiley & Sons, Ltd.