Maria Cristina Cassani

Synthesis of new heterodinuclear aminocarbyne complexes: crystal structures of [AuW{µ-CN(Et)Me}C6F5)(CO)2(η-C5H5)] and [{CuW{µ-CN(Et)Me}Cl(CO)2(η-C5H5)}2]

The aminocarbyne [W{CN(Et)Me}(CO)2(cp)]1(cp =η-C5H5) reacts with [Au(C6F5)(tht)](tht = tetrahydrothiophene) and CuCl to give the adducts [AuW{µ-CN(Et)Me}(C6F5)(CO)2(cp)]2 and [{CuW{µ-CN(Et)Me}Cl(CO)2(cp)}2]3 respectively which have been structurally characterized by X-ray diffraction. Complex 2 crystallizes in space group P, a= 9.840(5), b= 11.577(6), c= 8.296(6)A, α= 99.03(5), β= 91.01(6), γ= 81.92(4)°, Z= 2. Complex 3 crystallizes in space group P21/a, a= 7.788(2), b= 14.880(5), c= 11.712(5)A, β= 95.35(3)°, Z= 2. Both adducts exhibit a molecule of 1 bonded to Au(C6F5) or Cu2Cl2 fragments, respectively, through one of the W–C(carbyne)π bonds. A WCM ring is formed in which 1 preserves most of its identity and the coinage metals attain their preferred electron counts. The cationic Group 11 fragments [M(PPh3)+](M = Cu, Ag or Au) also react with complex 1 to form [M{W[µ-CN(Et)Me](CO)2(cp)}2]+5; when M = Au NMR spectroscopy indicates that in addition to the trinuclear species 5, the dimetallacyclopropene [AuW{µ-CN(Et)Me}(CO)2(cp)(PPh3]+4 is also present. All these adducts have been spectroscopically characterised.

Reactions of [Au(C6F5)(SC4H8)] with diazoalkanes. Synthesis and molecular structures of [Au(C6F5)(Ph2CNNCPh2)]

Abstract Treatment of [Au(C6F5)(SC4H5)] (1) (SC4H8=tetrahydrothiophene, tht) with Ph2CN2 affords the azine complex [A u(C 6 F 5 )(Ph 2 CN NCPh2)] (2), whereas HAuC14 reacts with diphenyldiazomethane to form the salt [Ph2CN(H)NCPh2][AuCl4] (3). The molecular structures of both 2 and 3 have been established by single crystal X-ray diffraction studies. Complex 2 (triclinic, P 1 , Z=2, a=10.805(4), b=13.066(2), c=10.094(3) A, α=112.06(3), β=100.63(2), γ=88.45(2)°) exhibits the expected linear coordination with the azine acting as N- monodentate ligand. Bond parameters of interest are AuC(perfluorophenyl) 1.992(6), AuN(azine) 2.069(5) A, CAuN 175.8(2)°. 3 (triclinic, P 1 , Z=1, a=9.145(5), b=9.333(1), c=8.228(3) A, α=100.08(1), β=107.30(3), γ=74.17(2)°) is an ionic species in which the cation is the monoprotonated derivative of the azine coordinated to gold in 2. Bond parameters within the azine motecule in the two derivatives are comparable. Complex 1 promotes dinitrogen elimination from diazofluorene to form fluoren-9-ylidene via carbene-carbene coupling. An interpretation of the different behaviour of the two diazocompounds is presented.

Reactions of [Fe2{μ-C(CN)SMe2} (μ-CO)(CO)2(Cp)2]-SO3CF3 (Cp = μ-C5H5) with alcohols

Abstract The reactions of [Fe 2 {μ-C(CN)SMe 2 }(μ-CO)(CO) 2)(Cp)[in2 ]SO 3 CF 3 (Cp = η-C 5 H 5 ) with alcohols and alkoxides have been investigated. Nucleophilic attack of the oxygen atom on the μ-C carbon with displacement of the Me 2 S molecule was observed in all cases. The resulting μ-cyanoalkoxycarbene derivatives [Fe 2 {μ-C(CN)OR}(μ-CO)(CO) 2 (Cp) 2 ] (R = Me, 2a ; Et, 2b ; i Pr, 2c ; CH 2 Ph, 2d ; CH 2 CHCH 2 , 2e ; CH 2 CH 2 NMe 2 , 2f ; CH 2 CH 2 OH, 2g ; C 6 H 5 , 3a ; C 6 H 4 - o -NO 2 , 3b ) have been characterized spectroscopically. The complex [Fe 2 {μ-C(CN)OCH 2 CHCH 2 }(μ-CO)(CO) 2 (Cp) 2 ] ( 2e ) undergoes a photolytically-promoted intramolecular CO substitution by the olefinic termination to give [Fe Fe{μ-C(CN)OCH 2 CH CH 2 }(μ-CO)(CO)(Cp) 2 ] ( 5 ), which was be subjected to an X-ray diffraction study. Some structural features were as expected, in particular the location of Cp in a cis disposition with respect to the CN group. The molecule is asymmetric as a consequence of the coordination of the allyl in the place of a terminal CO group; the configurations of the four chiral centres are discussed.

Cationic-anionic polyelectrolyte interaction as a tool to graft silver nanoparticles on hydroxyapatite crystals and prevent cytotoxicity

This paper reports an easy, green and low cost method to support silver nanoparticles (AgNPs) onto functionalized hydroxyapatite (HA) crystals. The process involves low molecular weight poly(ethylenimine) (PEI) as a reducing and stabilizing agent of AgNPs and polyacrylic acid (PAA) as a functionalizing agent of hydroxyapatite (HAPAA). With respect to HA, the negatively charged surface of HAPAA significantly improves the interaction with the positively charged surface of PEI-stabilized AgNPs. AgNPs content up to about 6.5 wt% in the composite HAPAA–AgNPs crystals has been obtained by varying the volume of the AgNPs suspension submitted to interaction with HAPAA. The cytotoxicity of the crystals, evaluated through in vitro tests on MG63 osteoblast-like human cells, increases on growing Ag content, but it is reduced by the presence of PAA. The HAPAA–AgNPs crystals display similar dose-dependent antibacterial activity towards gram-positive and gram-negative bacteria. The comparison of data indicates that an AgNPs content of about 2 wt% allows for combining absence of cytotoxicity with a significant long-standing antibacterial activity towards both Staphylococcus aureus and Escherichia coli.

RF-sputtering preparation of gold-nanoparticle-modified ITO electrodes for electrocatalytic applications

The preparation of gold-nanoparticle (AuNPs)-modified indium tin oxide (ITO) electrodes (AuNPs/ITO) was performed by radio-frequency (RF) sputtering from Ar plasmas at temperatures as low as 60 °C, tailoring the AuNP morphology and content as a function of the sole sputtering time. The latter parameter was varied from 5 to 20 min in order to investigate the influence of gold amount and distribution on the electrochemical performances of the resulting AuNPs/ITO systems. The electrodes were characterized using field emission-scanning electron microscopy (FE-SEM), UV-vis absorption and x-ray photoelectron spectroscopies (XPS); moreover variable scan rate cyclic voltammetry (CV) studies were performed to examine their electrochemical behavior. The electrocatalytic activity of the nanostructured AuNPs/ITO electrodes toward methanol oxidation was investigated and compared with a continuous gold film (Aufilm/ITO). The catalytic efficiency of the AuNPs/ITO systems was found to increase with the gold content and the AuNPs-support boundary region in the corresponding samples. For the longest sputtering time (i.e. 20 min) the performances of the nanostructured electrode were better than the Aufilm/ITO reference, despite the much lower catalyst amount. Furthermore, conversely from the AuNPs/ITO samples, in the Au(film)/ITO case the gold film displayed a poor adhesion to the substrate and the electrode could be used only for a limited number of electrochemical cycles.

Synthesis of dinuclear iron and ruthenium aminoalkylidene complexes and the molecular structure of the novel cis-[Ru2(CO)2(Cp)2{μ-C(CN)N(Me)Bz}2](Cp = η-C5H5; Bz CH2Ph)☆

Abstract Repeated stepwise addition of CH 3 SO 3 CF 3 and Bu 4 NCN to the diisocyanide complex [Ru 2 (CO) 2 (Cp) 2 (CNBz) 2 ] (Cp = η -C 5 H 5 ; BzCH 2 Ph) has led to the formation of the new bis- μ -aminoalkylidene complex [Ru 2 (CO) 2 (Cp) 2 { μ -C(CN)N(Me Bz} 2 ], which has been characterized by X-ray diffraction. The crystal contains a racemic mixture of the isomer with the same chirality at the amine nitrogens. The molecule conforms to a C 2 idealized symmetry. Selected bond distances are RuRu 2.662(1), Ru( μ -C) 2.088 (av), μ -CN(amine) 1.479 (av) A. All the intermediate species: [Ru 2 (CO) 2 (Cp) 2 ( μ -CNBz){ μ -CN(Me)Bz}SO 3 CF 3 , [Ru 2 (CO) 2 (Cp) 2 { μ -CNBz)} μ -C(CN)N(Me)Bz}] and [Ru 2 (CO) 2 (Cp) 2 { μ -CN(Me)Bz}{ μ -C(CN)-N(Me)Bz}]SO 3 CF 3 have been isolated and characterized spectroscopically. Attempts to extend the synthetic method to the iron diisocyanide [Fe 2 (CO) 2 (Cp) 2 (CNBz) 2 ] led to [Fe 2 (CO)(CNBz)(Cp) 2 ( μ -CO){ μ -CN(Me)Bz} SO 3 CF 3 and [Fe 2 (CO)(CNBz)-(Cp) 2 ( μ -CO)} μ -C(CN)N(Me)Bz}] but not to the bis(aminoalkylidene) derivative.

Mild fabrication of silica-silver nanocomposites as active platforms for environmental remediation

Herein we report a new, simple, low cost and one step way to obtain silica-supported silver nanoparticles (AgNPs) on commercial polyethyleneimine-functionalized silica beads (SiO2-PEI) under mild experimental conditions. The novel AgNPs/(SiO2-PEI) material has been thoroughly analyzed using FE-SEM, BET, XRD, XPS and XE-AES analysis. The reduction of Methylene Blue (MB) to Leuco Methylene Blue (LMB) in the presence of NaBH4 was chosen for testing the catalytic properties of AgNPs/(SiO2-PEI) towards dyes decoloration. Moreover, the prepared supported nanocatalyst was also found to exhibit excellent catalytic activity towards decoloration of some azo dyes such as E110 and E122.

Fluoroalkylsilanes with Embedded Functional Groups as Building Blocks for Environmentally Safer Self-Assembled Monolayers

The fabrication of silane-based fluorinated self-assembled monolayers (FSAMs) on indium tin oxide (ITO, a transparent electrode) was carried out making use of the following fluoroalkylsilanes (FAS): 2,2,3,3,4,4,5,5,6,6,6-undecafluoro-N-[3-(trimethoxysilyl)propyl]hexanamide (1; R(F) = C5F11) and 1,1,2,2,3,3,4,4,4-nonafluoro-N-[3-(trimethoxysilyl)propyl]butane-1-sulfonamide (2; R(F) = C4F9), containing an embedded amide and a sulfonamide group, respectively, between the short perfluoroalkyl chain (R(F) with C < 6) and the syloxanic moiety. The obtained FSAM-modified/ITO systems were characterized by X-ray photoelectron spectroscopy (XPS), contact angle (CA), surface energy measurements, and electrochemical impedance spectroscopy (EIS) and compared to ITO modified with a 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyltriethoxysilane (3; R(F) = C6F13), with the perfluoroalkyl group linked to the syloxanic moiety through a simple hydrocarbon chain. The results obtained show that the presence of the -NHCO- and -NHSO2- groups have a different mode of action and, with the former, despite the short perfluoroalkyl chain, the ITO-1 system presents a CA (Θ(water )= 113.5°) and surface energy (γl = 14.0 mJ m(-2)) typical of amphiphobic materials. These properties can be exploited in a variety of applications, such as self-cleaning, anti-fouling, and anti-fingerprint coatings, and in advanced microelectronic components.

Homogeneous catalytic hydrogenation of perfluoro methyl esters

The first example of perfluoroalkyl methyl ester RfC(O)OMe (Rf = C3F7, C5F11) reduction by homogeneous catalytic hydrogenation with the ruthenium catalyst Ru-MACHO™ is herein reported. The hydrogenation process leads to the corresponding perfluorinated alcohols thus replacing sodium borohydride that has so far represented the state of art in perfluoro ester reduction.

The μ-sulfonium–methylidene diiron complexes [Fe2{μ-C(X)SMe2}(μ-CO)(CO)2(Cp)2]SO3CF3 (X=CN, H) as precursors of μ-alkylidene complexes

Abstract The reactions of [Fe 2 {μ-C(X)SMe 2 }(μ-CO)(CO) 2 (Cp) 2 ]SO 3 CF 3 (X=CN 2a , H 2b ; Cp=η-C 5 H 5 ) with Li 2 Cu(CN)R 2 (R=Me, Bu n , Ph, CCC 6 H 4 Me-4, C 4 H 3 S) give the neutral μ-alkylidene complexes [Fe 2 {μ-C(X)R}(μ-CO)(CO) 2 (Cp) 2 ] ( 3 ) arising from nucleophilic attack at the bridging carbon and SMe 2 displacement. Likewise, 2a , b react with the sodium salt of dimethylmalonate, diethylmalonate, ethylacetoacetate, 2,4-pentanedione, dibenzoylmethane and benzylcyanide, resulting in the formation of the corresponding functionalized μ-alkylidene complexes [Fe 2 {μ-C(X)R}(μ-CO)(CO) 2 (Cp) 2 ] ( 5 – 7 ) (X=CN, H; R=CH(COOMe) 2 , CH(COOEt) 2 , CH(COOMe)(COMe), CH(COMe) 2 , CH(COPh) 2 , CH(Ph)CN). The dichetone adducts [Fe 2 {μ-C(X)CH(COR) 2 }(μ-CO)(CO) 2 (Cp) 2 ] (X=CN, H; R=Me, Ph) undergo deacylation upon treatment with alumina, leading to the formation of the complexes [Fe 2 {μ-C(X)CH 2 C(O)R}(μ-CO)(CO) 2 (Cp) 2 ]. Reactions of 2a , b with LiBu or PhLi result in the formation the metallacycles [Fe 2 {μ-C(X)S(Me) CH 2 }(μ-CO)(C O)(CO)(Cp) 2 ] (X=CN, 4a ; H 4b ) which arise from the deprotonation of an SMe group and the intramolecular addition at a terminally coordinated carbonyl. Finally, a comparison of the reactivity of 2a , b with that of the μ-carbyne diiron complexes [Fe 2 (μ-CX)(μ-CO)(CO) 2 (Cp) 2 ]SO 3 CF 3 (X=H, SMe, NMe 2 ) is presented.