Structural variations, electrochemical properties and computational studies on monomeric and dimeric Fe-Cu carbide clusters, forming copper-based staple arrays

The halide ligands of [Fe4C(CO)12(CuCl)2]2- (1) and [Fe5C(CO)14CuCl]2- (2) can be displaced by N-, P- or S-donors. Beside substitution, the clusters easily undergo structural rearrangements, with loss/gain of metal atoms, and formation of Fe4Cu/Fe4Cu3 metallic frameworks. Thus, the reaction of 1 with excess dppe yielded [{Fe4C(CO)12Cu}2(\uf06d-dppe)]2- (3). [{Fe4C(CO)12Cu}2(\uf06d-pyz)]2- (4) was obtained by reaction of 2 with Ag+ and pyrazine. [Fe4C(CO)12Cu-py]- (5) was formed more directly from [Fe4C(CO)12]2-, [Cu(NCMe)4]+ and pyridine. [Fe4Cu3C(CO)12(\uf06d-S2CNEt2)2]- (6) and [{Fe4Cu3C(CO)12(\uf06d-pz)2}2]2- (7) were prepared by substitution of the halides of 1 with diethyldithiocarbammate and pyrazolate, in the presence of Cu(I) ions. All these products were characterized by X-ray analysis. 3 and 4 and 5 are square based pyramids, with iron in the apical sites, the bridging ligands connect the two copper atoms in 3 and 4. 6 and 7 are octahedral clusters with an additional copper ion held in place by the two bridging anionic ligands, forming a Cu3 triangle with Cu-Cu distances ranging 2.63-3.13 \uc5. In 7, an additional unbridged cuprophilic interaction (2.75 \uc5) is formed between two such cluster units. DFT calculations were able to reproduce the structural deformations of 3-5, and related their differences to the backdonation from the ligand to Cu. Additionally, DFT found that, in solution, the tight ion pair [NEt4]27 is almost isoenergetic with the monomeric form. Thus, 3, 4 and 7 are entities of nanometric size assembled either through conventional metal-ligand bonds, or weaker electrostatic interactions. None of them allows electronic comunication between the two monomeric units, as shown by electrochemistry and spectroelectrochemical studies

Molecular magnetic quantum dots in multivalent metal cluster compound

Quantum Matter and Optic

Interpretation of the terminal v(co) spectra of some M5 transition metal carbonyl clusters

The n(CO) spectra of 31 M5 transition metal carbonyl clusters are interpreted in terms of the spherical harmonic and tensor harmonic models. It seems that the former is that which is generally applicable but that the splittings of the (spherical) P mode are larger than had previously been considered indicative of this model. An explanation in terms of the cluster asymmetry is suggested

Mixed Co-Ni carbide clusters. Part 1. Synthesis and structural characterization of the [Co3Ni9C(CO)20]3- trianion

Reaction of [Co3(CO)9CCl] with [Ni6(CO)12]2\u2013 results in a complicated mixture of mixed Co\u2013Ni carbide carbonyl clusters, among which the [Co3Ni9C(CO)20]3\u2013 trianion has been isolated in a pure crystalline state and fully characterized by X-ray crystallography. The metal framework of this compound is unprecedented in cluster geometries and may be described as a square antiprism of metal atoms tetra-capped on two alternate pairs of adjacent triangular faces. Despite the presence of a caged carbon atom in the square-antiprismatic cavity, the compound is readily degraded by carbon monoxide (25 \ub0C, 1 atm) mainly to a mixture of [Co(CO)4]\u2013 and [Ni(CO)4]. Corresponding degradation of the cluster under a mixture of carbon monoxide and hydrogen yields, in addition, trace amounts of organics, mainly C1 and C2 hydrocarbons, probably derived from the carbide atom

N-heterocyclic carbene copper complexes tethered to iron carbidocarbonyl clusters

The reactions of [Fe4C(CO)12(CuNCMe)x]x - 2(x = 1, 2) with ImiPr\ub7HBF4(ImiPr = N,N\u2032-bis(isopropyl)imidazol-2-ylidene) in the presence of NaH yielded [Fe4C(CO)12(CuImiPr)x]x - 2. The hetero-substituted [Fe4C(CO)12(CuCl)(CuImiPr)]-was obtained by the deprotonation of the corresponding chloride salt. All products have been characterized by elemental analysis, NMR and single crystal X-ray diffraction analyses

A traditional synthetic method, and a new structural motif, for molybdenum-gold clusters: synthesis and solid-state structure of a Au8[Mo(CO)5)4(PPh3)4

The neutral cluster [Au8Mo4(CO)(20)(PPh3)(4)] was synthesized in low yield from [AuCl(PPh3)] and [Mo-2(CO)(10)](2-) in acetonitrile at room temperature. The cluster was characterized by X-ray analysis, IR, and P-31 NMR spectroscopy. Its solid-state structure consists of four Au3Mo tetrahedral units, fused by four Au atoms in a ring. The average bond lengths are Au-Au 2.77 angstrom and Mo-Au 2.93 angstrom. The internal angles of the planar square ring are very close to 90 degrees

Ag4(NHC)4(NO3)4: a Tetrameric Silver (I) Complex with Bridging N-Heterocyclic Carbene Ligands

In recent years the coordination chemistry of N-heterocyclic carbene showed a boosting increment, since these new types of ligands have many valuable properties in terms of stability, versatility, possibility to introduce new functionalities.1 Silver complexes are among the most widely studied since they have been used for several applications, including pharmaceutical, photophysical and catalytic.2 In such a large number of characterized compounds, only two examples of bridging coordination of the NHC groups have been reported, one for copper complex,3 and the other (with silver) assisted through symmetric pendant donor groups.4 Looking for new neutral silver complexes, we explored the reaction between Ag(cod)NO3 and [Ag(IPrIm)Cl]2, in CH2Cl2. The product was crystallized by diffusion of heptane, and the final yield was about 50 %. IR , elemental analyses and X-ray diffraction concurred to establish the actual formula of the compound as (HNC-Ag-NO3)4 In the solid state, the compound is composed by tetrameric unit with two short and one long Ag-Ag contacts. The short ones are bridged by the N-heterocyclic carbene, and the long one by monodendate nitrate anions. According to DFT calculations, the tetramer can exist in two isomers and the one with terminal-only carbene ligands should be slightly more stable. Conversely, with other anions such as halide, only one isomer can be formed. \uf023 Dedicated to the memery of Mario Manassero 1. Special issues on metal-carbene complexes: a) Dalton. Trans., 2013, 42, 7245-7432; b) Dalton. Trans., 2009, 6873-7316; c) Coord. Chem. Rev., 2007, 251, 595-896 d) Chem. Rev., 2009, 109, 3209-3884; e) Jones, W.D.; J. Am. Chem. Soc., 2009, 131, 15075-15077 f) J. Organomet. Chem.., 2005, 690, 5397-6252 2. Garrison, J.C.; Youngs, W.J.; Chem. Rev.,2005, 105, 3978-4008. 3. Han, X.; Koh, L.-L.; Liu, Z.-P.; Weng, Z.; Hor, T.S.A.; Organometallics, 2010, 29, 2403-2405 4. Garrison, J. C.; Simons, R. S.; Kofron, W. G.; Tessier, C. A.;Youngs, W. J. Chem. Commun. 2001, 1780\u20131781