Claudio Lo Sterzo

Response of a Pt-polyyne membrane in surface acoustic wave sensors: Experimental and theoretical approach

A surface acoustic wave (SAW) sensor, based on a polymeric sensitive membrane, has been realized for sensor applications and materials characterization. A platinum-containing rigid-rod organometallic polymer [-Pt(PPh3)2(-C≡C-pC6H2(2,5-OC16H33)2-C≡C-)]n (Pt–P–HDOB), obtained by the reaction of cis-[Pt(PPh3)2Cl2] with 1,4-diethynyl-2,5-dihexadeciloxybenzene (HDOB) by means of the recently assessed “Extended one pot” polymerization route, was here studied. The chemical structure and chain length of Pt–P–HDOB polymer were defined by spectroscopic techniques and gel permeation chromatography measurements. The acoustic characterization of the Pt–P–HDOB film was developed with the aid of the perturbation theory applied to different polymer-coated-piezoelectric substrates and the shear modulus of Pt–P–HDOB film have been estimated. A SAW delay line has been implemented on ZnO/Si substrate and a thin polymeric film has been spin deposited on the device surface to realize a chemical sensor. The sensor has been expo...

A convenient short cut from aromatic iodides to alkynylstannanes and their use for the straightforward preparation of polyacetylene and polymetallaacetylene polymers

Abstract The palladium-catalyzed cross-coupling reaction (Stille coupling) of aromatic iodides ArI and tributyl(ethynyl)tin Bu3SnCCH form the aromatic acetylides ArCCH and the side product tributyltin iodide Bu3SnI in equimolar amount. In situ addition of lithium diisopropylamide (LDA) to this crude mixture directly affords the tributyl(ethynyl)tin aromatics ArCCSnBu3 in high yield. In the case of the bis(iodoaromatic) IArI (Ar=phenyl, thiophene), this straightforward transformation affords the corresponding bis[tributyl(ethynyl)tin]derivative Bu3SnCCArCCSnBu3. In the presence of Pd this latter species can be directly reacted with a second bis(iodoaromatic) or a bis(metaliodide) unit to form acetylenic and metallaacetylenic polymers with tailored monomer units inserted in a stereoregular polymer chain.

Antioxidant capacity index based on gold nanoparticles formation. Application to extra virgin olive oil samples

A simple gold nanoparticles (AuNPs) based colorimetric assay for the antioxidant activity determination has been developed. The AuNP formation is mediated by extra virgin olive oil (EVOOs) endogenous polyphenols; the reaction is described by a sigmoidal curve. The ratio KAuNPs/Xc(50) (slope of the linear part of the sigmoid/concentration at half value of the absorbance) was found to be the optimal parameter to report the antioxidant capacity with respect to the single KAuNPs or Xc(50) values. The obtained data demonstrated that the compounds with ortho-diphenols functionality are most active in reducing gold (III) to gold (0). Thus, intermediate activity was found for gallic acid, while tyrosol (mono-phenols) had a significant lower activity than the others antioxidant compounds (at least one order of magnitude). In the analysis of olive oil samples, a significant correlation among classical methods used to determine antioxidant activity and the proposed parameter was found with R values in the 0.96-0.97 range.

An efficientone-pot access to poly(arylene ethynylene) homopolymers: Use of the Bu3Sn?moiety as a recyclable carrier to introduce the ethynyl unit into the chain

The palladium-catalyzed Stille coupling of an aromatic diiodide with half an equivalent of tributyl(ethynyl)tin results in a complex mixture containing the diethynylaromatic compound, the iodo(ethynyl)aromatic compound, unreacted diiodide and the tributyltin iodide side product. Addition of LDA to this mixture, while leaving the iodoaromatic moieties unaffected, causes deprotonation of the ethynyl functionalities, which immediately recombine with tributyltin iodide to form a mixture of bis(tributylethynyltin)aromatic, iodo(tributylethynyltin)aromatic, and unchanged diiodide. Being the palladium catalyst still active, it is sufficient to warm up this mixture to obtain the coupling of the tributylethynyltin and iodo moieties resulting in the formation of a poly(arylene ethynylene) polymer. Isolation of the polymer is easily and rapidly achieved by precipitation, while distillation of the mother liquor allows recovery of the tributyltin iodide side product. The latter can be utilized for the preparation of new tributyl(ethynyl)tin, thus allowing a convenient turnover of the tributyltin moiety.

Formation of metal σ-acetylides of Mo, W, and Ru via palladium-catalyzed metal-carbon coupling

The cyclopentadienyl metal complexes [(η5-C5H5)M(CO)nI] (1, M = Mo, n = 3; 2, M = W, n = 3; 3, M = Ru, n = 2) react with tributyltin acetylides Bu3Sn-CC-R (4, R = H;5, R = Pr; 6, R = Ph) in the presence of 5 mol% of [(CH3CN)2PdCl2] to give the corresponding σ-alkynyl metal complexes [(η5-C5H5)M(CO)n-CC-R] in good yield.

Formation of Mo, W, Fe and Ru di(metal σ-acetylide) derivatives of 2.5-diethynylthiophene via palladium-catalyzed metal-carbon coupling

Abstract In the presence of catalytic amount of bis(acetonitrile)dichloropalladium(II) [(CH3CN)2PdCl2] the iodocyclopentadienylmetal complexes [(η5-C5H5) M(CO)nI](1, M  Mo, n = 3; 2, M  W, n = 3; 3, M  Fe, n = 2, 4, M  Ru, n = 2) couple in a 2 to 1 ratio with 2,5-bis[(tributyltin)ethynyl]thiophene (5), to form the corresponding dimetal derivatives of general formula [(μ-C4H2SCC-2,5){(C5H5)M(CO)n}2] (6, M  Mo, n = 3; 7, M  W, n = 3; 8, M  Fe, n = 2; 9, M  Ru, n = 2).

A new frontier in the metal-catalyzed cross-coupling reaction field. The palladium-promoted metal–carbon bond formation. Scope and mechanism of a new tool in organometallic synthesis

Abstract The synthetic uses and the investigation of the reaction mechanism of the Pd-catalyzed metal–carbon bond-formation process are accounted. Preparations of simple σ-metal metal acetylides of type M–CC–R (M=Fe, Ru, Mo, W; R=H, Alkyl, Ph), homo and heterobimetallic complexes of type M–CC–Thiop–CC–M′ (Thiop=2,5-thiophene; M, M′=Fe, Ru, Mo, W), polymetallaacetylide tethers of type M–CC–Thiop–CC–M′(η 5 -Cp)–CC–Thiop–CC–(η 5 -Cp)M′–CC–Thiop–CC–M (M=Re, Mn; M′=Fe), and metallaacetylide polymers of type [–M–CC–Ar–CC–] n (Ar=2,5-thiophene, 1,4-phenylene) are reported. By the use of properly designed model substrate principal intermediates (i.e. oxidative addition, transmetalation) involved in the catalytic cycle have been isolated and fully characterized. Kinetic and spectroscopic studies of the reaction mechanism have evidenced that, depending from the reaction conditions, the transmetalation step may proceed by two pathways: (i) in concentrated solutions of the complex of oxidative addition (≅10 −2 M), transmetalation occurs through the formation of the intermediate species which is an associative complex between the substrate and the organostannane (associative mechanism). (ii) When transmetalation is performed using the complex of oxidative addition in lower concentrations (≅10 −4 M), the reaction proceeds through formation of a highly-reactive solvent-coordinate species (dissociative mechanism). These results are showing clear analogies with mechanistic studies of the carbon–carbon coupling process, thus with the use of these model substrates, a unique opportunity to investigate factors affecting the metal–carbon bond formation reaction is offered, as well as the possibility to shed light on unclear aspects of the carbon–carbon coupling itself, a phenomenon of paramount importance in synthetic organic chemistry.

USE OF THE STILLE COUPLING TO LABEL STEROIDS WITH THE ETHYNYLCYCLOPENTADIENYLMANGANESETRICARBONYL MOIETY

Abstract In order to use FT-IR spectroscopy as a technique for immunoassay analysis, the introduction of metallocarbonyl markers in steroids has been studied. By the use of the palladium-catalyzed cross-coupling reaction of steroidal triflates with [trimethyltin ethynyl η5-cyclopentadienyl manganesetricarbonyl it has been possible to label some steroids with the manganesetricarbonyl moiety. In the case of testosterone, by means of a properly designed synthetic route, it has been possible to introduce the organometallic marker minimizing the impact on the original structure and on the functional groups of the natural hormone thus making this labelled species particularly suitable for CMIA ( C arbonyl M etallo I mmuno A ssay) purposes.

Methyliodine exchange in (η5-iodocyclopentadienyl)metallo methyl derivatives of iron(II), tungsten(II), and molybdenum(II) in the presence of palladium

Abstract A new and unexpected interchange reaction has been discovered during an attempt to make fulvalene-linked heterobimetallic complexes by palladium-catalyzed coupling between η 5 -(iodo)cyclopentadienyl and η 5 (trimethyltin)cyclopentadienyl metal complexes. In the presence of Pd the (η 5 -iodocyclopentadienyl)metallo methyl derivatives of general formula (η 5 -IC 5 H 4 )M(CO) n CH 3 (M = Fe, n = 2; M = W, n = 3; M = Mo, n = 3) undergo methyl-iodine exchange, to give the corresponding (η 5 -CH 3 C 5 H 4 )M(CO) n I complexes. The palladium(0) catalysis of the reaction apparently involves an intramolecular transmetallation.

Dalton communications. An unprecedented palladium-catalysed carbon–metal bond formation

The reaction of [Fe(η5-C5H4R)(CO)2I](R = styryl) with [Mn(η5-C5H4CCSnMe3)(CO)3] in dimethylformamide in the presence of catalytic amounts (5%) of [PdCl2(MeCN)2] produces [(OC)2(η5-RC5H4)Fe–CC–(η5-C5H4)Mn(CO)3] in good yield; the crystal structure of the tetrahedral pyramidal adduct formed by reaction of this coupled product with [Co2(CO)8] has been determined.