Reactions of Ru3(CO)12 with Ene-yne and Alkoxy-silyl Functionalized Compounds. The Crystal Structure of (μ-H)Ru3(CO)9[μ3-η2-HC=N(CH2)3Si(OEt)3]

Ru₃(CO)₁₂ has been reacted with the compounds hex-1-en-3-yne [EtC≡CCH=CH₂], 2-methyl-hex-1-en-3-yne [EtC≡CC(=CH₂)CH₃] and with 3(ethoxy-silyl)propyl isocyanate [(EtO)₃Si(CH₂)₃NCO] and the compound tb [(EtO)₃Si(CH₂)₃NHC(=O)OCH₂C≡CCH₂OC(=O)NH(CH₂)₃Si(OEt)₃] in hydrocarbon solution. Some reactions in CH₃OH/KOH solution (followed by acidification) have also been performed. The main products of the reactions with ene-ynes are the clusters Ru₃(CO)₆(μ-CO)₂L₂ (L = C₆H₈, C₇H₁₀) and their demolition products, the “ferrole” Ru₂(CO)₆L₂ complexes. One of the isomers of Ru₃(CO)₆(μ-CO)₂L₂, and Ru₂(CO)₆L₂ (L = C₇H₁₀) have been reacted with vinyl-triethoxysilane [(EtO)₃SiCH=CH₂]: these reactions did not afford complexes containing new carbon–carbon bonds or triethoxy-silyl groups. Only polymerization of vinyl-triethoxysilane occurred. The reactions of Ru₃(CO)₁₂ with triethoxysilyl-propyl-isocyanate and tb (in the presence of Me₃NO) lead to the same products, that is the isomeric complexes (μ-H)Ru₃(CO)₉[C=N(H)(CH₂)₃Si(OEt)₃] with a “perpendicular” ligand (complex 3, as proposed on the basis of spectroscopic results) and (μ-H)Ru₃(CO)₉[HC=N(CH₂)₃Si(OEt)₃] with a “parallel” ligand (complex 4, as confirmed by a X-ray analysis). The reaction pathways leading to these products are discussed. Complex 4 has been reacted with tetraethyl orthosilicate and the resulting material has been characterized. These reactions are part of a study on the synthesis of inorganic-organometallic materials through sol–gel techniques. This paper is dedicated to Prof. Gunther Schmid in the occasion of his 70th birthday.     

Particle image velocimetry measurements of a shock wave/turbulent boundary layer interaction

Particle image velocimetry is used to investigate the interaction between an incident shock wave and a turbulent boundary layer at Mach 2.1. A particle response assessment establishes the fidelity of the tracer particles. The undisturbed boundary layer is characterized in detail. The mean velocity field of the interaction shows the incident and reflected shock wave pattern, as well as the boundary layer distortion. Significant reversed flow is measured instantaneously, although, on average no reversed flow is observed. The interaction instantaneously exhibits a multi-layered structure, namely, a high-velocity outer region and a low-velocity inner region. Flow turbulence shows the highest intensity in the region beneath the impingement of the incident shock wave. The turbulent fluctuations are found to be highly anisotropic, with the streamwise component dominating. A distinct streamwise-oriented region of relatively large kinematic Reynolds shear stress magnitude appears within the lower half of the redeveloping boundary layer. Boundary layer recovery towards initial equilibrium conditions appears to be a gradual process.     

Imaging polycrystalline and smoke MgO surfaces with atomic force microscopy: a case study of high resolution image on a polycrystalline oxide

Atomic force microscopy in contact, non-contact and in high resolution modes have been used to image MgO powder samples, obtained at different degree of sintering, starting from Mg(OH)₂ decomposition or obtained in form of smoke. From high resolution AFM images of MgO smoke, the lattice periodicity on regular surfaces has been revealed for the first time, under ambient conditions. The high surface perfection of the microcrystals has been further confirmed by HRTEM analysis. To obtain more information on the local structure of the single faces, in terms of type and distribution of the surface active sites, the adsorption of a simple probe molecule (CO) on such surfaces has been investigated by means of FTIR spectroscopy.     

Structural characterization of electrodeposited copper hexacyanoferrate films by using a spectroscopic multi-technique approach

A deep structural investigation predominantly by X-ray spectroscopic techniques is conducted on films of copper hexacyanoferrate (CuHCF) deposited under different conditions, aimed at establishing structure-properties relationships. We show that the potentiodynamic electrosynthesis of CuHCF on carbon-based surfaces produces a highly disordered material, with a variable amount of Prussian Blue (PB). The subsequent Cu(2+) intercalation induces the partial conversion of PB into CuHCF, which explains the improved electrocatalytic properties after the intercalation process. Both Cu and Fe K-edge data have been recorded. For the sample with the lower amount of PB, we could perform a multiple edge data analysis to determine the local atomic environment around both metal centres using the same set of structural parameters. The presence of high multiplicity Cu-N-C-Fe linear chains has allowed us to determine accurately the local environment of Fe while fitting the Cu K-edge data only. Using this approach we have retrieved structural information around Fe for those samples in which the concomitant presence of PB would have made impossible the analysis of the Fe K-edge. The Fe-C, C-N and Cu-N bond distances have been found in agreement with those of the bulk structures, but higher values of [Fe(CN)(6)] vacancies for the building blocks have been evidenced, reaching a value of ~45% in one sample. XANES, Raman and SEM data agree with the model proposed for each studied electrode.     

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.     

Syntheses of chromium tricarbonyl organometals of 1-methyl-naphthalene and different polycyclic aromatic hydrocarbons,characterisation of the (C11H10)Cr(CO)3 isomers and the crystal structure of the [(η6-5,6,7,8,9,10-C11H10)Cr(CO)3] complex

The synthesis of organometal complexes from chromium hexacarbonyl with 1-methyl-naphthalene ligand is reported. Two arene-chromium-tricarbonyl isomers are formed at competitive yields, featured with the metal fragment coordinated to both the methylated and the benzenic aromatic ring. A single-crystal X-ray diffraction measurement has been performed on the [(η⁶-5,6,7,8,9,10-C₁₁H₁₀)Cr(CO)₃] isomer, which presents the metal carbonyl moiety attached to the benzenic arene ligand. The products of reaction have been studied by UV–VIS–NIR, fluorescence and ¹H NMR spectroscopies. A detailed vibrational characterisation by mean of experimental FT-IR and Raman spectroscopy and DFT calculations is reported. The electron ligand donation to the metal carbonyl system, determined by FT-IR spectroscopy, has been related to the actual decrease of resonance energy of the aromatic hydrocarbon in the complex and compared with other chromium tricarbonyl complexes of different polycyclic aromatic hydrocarbons provided with the naphthalenic moiety.     

Development of a tandem thin-layer chromatography-high-performance liquid chromatography method for the identification and determination of corticosteroids in cosmetic products

A solid-phase extraction clean-up and and a liquid chromatographic method with ultraviolet detection were developed for the analysis of 51 corticosteroids in cosmetic samples in order to screen commercial samples for the presence of undeclared synthetic corticosteroids. A thin-layer chromatographic analysis was carried out on silica gel plates, using different eluants and detection reagents. When such a preliminary chromatographic separation gave some indications about the presence of steroid compounds, the methanol extracts from real samples were applied to a solid-phase extraction C₁₈ cartridge, and the analytes eluted with ethyl ether. The high-performance liquid chromatographic separation was then carried out for the identification and determination of the analytes using a Purospher RP-18 column, an isocratic or a gradient elution with a mixture acetonitrile-water and a photodiode-array detector. The accuracy of the method was determined by spiking experiments on home-made cosmetic samples. The analytical recoveries were satisfactory.