Vincenzo Busico

University of Naples Federico II, Napoli, Campania, Italy

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Publications (129)429.57 Total impact

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    ABSTRACT: Extensive benchmarking of functionals and basis sets against CCSD(T,FULL) results.•TS, π-coord., reaction energies and agostic interactions for early and late TM.•M06-2X for ETM (MAD 1.0).•TPSSh-D0 for LTM (MAD 1.3) and acceptable “across-the-board functional”.•Ethene insertion barriers:∼0 for titanocenes, few kcal/mol for zirconocenes and CGC.
    Journal of Organometallic Chemistry 01/2015; 775. · 2.00 Impact Factor
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    ABSTRACT: The intermolecular alkoxylation of alkynes is the oldest application of cationic gold(I) catalysts; however, no systematic experimental data about the role of the anion are available. In this contribution, the role of the anion in this catalytic reaction as promoted by a N-heterocyclic carbene-based gold catalyst, [(NHC)AuX] (X=BARF−, BF4−, OTf−, OTs−, TFA−, or OAc−) is analyzed, through a combined experimental (NMR spectroscopy) and theoretical (DFT calculation) approach. The most important factor seems to be the ability to abstract the proton from the methanol during the nucleophilic attack, and such ability is related to the anion basicity. On the other hand, too high coordination power or basicity of the anion worsens the catalytic performance by preventing alkyne coordination or by forming too much free methoxide in solution, which poisons the catalyst. The intermediate coordinating power and basicity of the OTs− anion provides the best compromise to achieve efficient catalysis.
    Chemistry - A European Journal 09/2014; · 5.93 Impact Factor
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    ABSTRACT: Multi-frequency continuous-wave and pulsed EPR techniques are employed to investigate Ti(iii)-chloro complexes obtained by dissolving TiCl3 in anhydrous and hydrated methanol. Two distinctly different species, characterized by different g matrices are observed in the two cases. Hyperfine sublevel correlation (HYSCORE) spectroscopy is found to be a powerful method to identify the type of nuclei surrounding the Ti(3+) ion. For the first time, the hyperfine and nuclear quadrupole data of Ti(iii)-bound (35/37)Cl nuclei are reported together with (1)H and (13)C hyperfine data of the coordinated methanol molecules. DFT modelling allows interpreting the measured spin Hamiltonian parameters in terms of microscopic models of the solvated species. The theoretical observable properties (g matrix, (35/37)Cl, (1)H and (13)C hyperfine tensors) are in quantitative agreement with the experiments for two families of complexes: [TiCln(CH3OH)6-n]((3-n)+) (with n ranging from 1 to 3) and [Ti(CH3OH)5(OH)](2+) or [Ti(CH3OH)5(OCH3)](2+). The first complex is observed in anhydrous methanol, while the second type of complex is observed when water is added to the solution, the presence of OH(-) and/or CH3O(-) species being promoted by water hydrolysis. The results obtained for the frozen solutions are critically compared to EPR spectra recorded for a MgCl2-supported Ti-based Ziegler-Natta model catalyst.
    Physical Chemistry Chemical Physics 08/2014; · 4.20 Impact Factor
  • Roberta Cipullo, Simona Mellino, Vincenzo Busico
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    ABSTRACT: A simple method for the counting and structural elucidation of the different active sites in an olefin polymerization catalyst system is introduced, based on a reaction quench by O2 under controlled kinetics, followed by NMR analysis of the OH‐labeled chain end‐groups formed upon acidic work‐up of the polymer. The method is successfully benchmarked using a molecular bis(phenoxyamino)Zr(IV)‐based catalyst characterized by a comparatively long‐lasting controlled kinetic transient at room temperature. A simple method of chain‐end labeling with dioxygen under controlled kinetic conditions is applied to count and structurally identify the active sites in olefin homo‐ and copolymerization processes mediated by a post‐metallocene catalyst.
    Macromolecular Chemistry and Physics 07/2014; · 2.39 Impact Factor
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    ABSTRACT: NMR spectroscopy and DFT studies indicate that the Symyx/Dow Hf(IV)-pyridylamido catalytic system for olefin polymerization, [{N(-) ,N,CNph (-) }HfMe][B(C6 F5 )4 ] (1, Nph=naphthyl), interacts with ERn (E=Al or Zn, R=alkyl group) to afford unusual heterobimetallic adducts [{N(-) ,N}HfMe(μ-CNph )(μ-R)ERn-1 ][B(C6 F5 )4 ] in which the cyclometalated Nph acts as a bridge between Hf and E. (1) H VT (variable-temperature) EXSY NMR spectroscopy provides direct evidence of reversible alkyl exchanges in heterobimetallic adducts, with ZnR2 showing a higher tendency to participate in this exchange than AlR3 . 1-Hexene/ERn competitive reactions with 1 at 240 K reveal that the formation of adducts is strongly favored over 1-hexene polymerization. Nevertheless, a slight increase in the temperature (to >265 K) initiates 1-hexene polymerization.
    Angewandte Chemie International Edition 02/2014; 53:2157-2161. · 11.34 Impact Factor
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    ABSTRACT: Alkyl/halide bridged aluminium systems, relevant to e.g. olefin polymerization are known problem cases for DFT. ‘Chemical accuracy’ can be reached with the M06-2X functional or TPSSTPSS-D2. Alkylation of olefin polymerization catalyst precursors is exergonic for most electronegative groups X (F, Cl, OR, NR2) provided the Me2AlX-dimerization energies are taken into account.
    Journal of Organometallic Chemistry 01/2014; s 772–773:161–171. · 2.00 Impact Factor
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    ABSTRACT: The adsorption of small probe molecules (H2O, NH3 and EtOH) and the small model silane Me2Si(OMe)2 on (104) and (110) surfaces of α-MgCl2 have been studied using periodic DFT calculations including a classical correction (of the type f(R)/R6) for dispersion. The results reveal that donors strongly stabilize both crystal surfaces relative to the bulk solid. Moreover, coordination of two donor molecules to the four-coordinate exposed Mg atom of MgCl2 (110) causes this surface to become preferred over MgCl2 (104) surface with only a single donor per exposed Mg. However, coverage also plays an important role. The model silane preferentially adsorbs in bidentate mode on MgCl2 (110), provided that coverage is 0.5 or lower; at full coverage, there is not enough space for such an arrangement, and only a monodentate binding mode is obtained. Such coverage effects should be even more pronounced for the bulkier silanes used as external donors in real MgCl2-supported Ziegler–Natta systems, as tailored experiments seem to confirm.
    The Journal of Physical Chemistry C 11/2013; 117(46):24345–24353. · 4.84 Impact Factor
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    ABSTRACT: Diffusion NMR spectroscopy was applied to investigate all individual components and combinations thereof for the Cp2ZrMe2/MAO (DMAO)/TBP (MAO = methylaluminoxane, DMAO = AlMe3 depleted MAO, TBP = 2,6-di-tert-butylphenol) ternary system, selected as a prototypical catalytic pool for homogeneous olefin polymerisation. Both MAO and DMAO were found to self-aggregate in C6D6 with the latter having a higher propensity. TBP reacts with DMAO affording MeAl(2,6-di-tert-butylphenoxide)2 and causing a structural modification of DMAO, whose aggregates become much larger. The actual dimensions and self-aggregation tendency of (D)MAO, which depend on Al concentration and the possible presence of TBP, turned out to carry over to [Cp2Zr(μ-Me)2AlMe2]MeMAO () OSIP (outer sphere ion pair) and [Cp2Zr(+)MeMeMAO(-)] () ISIP (inner sphere ion pair) that form upon activation of Cp2ZrMe2. Once the intrinsic self-aggregation tendency of MAO has been subtracted, OSIP and ISIP behave exactly as analogous ion pairs with borate ions: ISIP does not self-aggregate, whereas OSIP exhibits the same self-aggregation trends of zirconocene OSIPs with borate counterions.
    Dalton Transactions 03/2013; 42:9104. · 4.10 Impact Factor
  • Vincenzo Busico
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    ABSTRACT: The future of polyolefin-based materials and the opportunities for further research and development in Ziegler-Natta catalysis are discussed. Thorough control of polymer microstructure and architecture ensured by modern olefin polymerization catalysts and processes warrants further progress in fundamental and applied research for many years to come.
    MRS Bulletin. 03/2013; 38(03).
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    ABSTRACT: The productivity of a number of bis-(phenoxyamine)Zr(IV)-based catalysts (bis(phenoxyamine) = N,N′ -bis(3-R1 -5-R2 -2-O-C6H2CH2 )-N,N′ -(R3 )2 -(NCH2CH2N)) in ethene and propene polymerization was evaluated for different R1/R2/R3 combinations. In previous studies on this class we demonstrated that the cations that form upon precatalyst activation (e.g., by methylalumoxane) adopt a “dormant” mer-mer geometry, and an endothermic isomerization to the active fac-fac geometry is the necessary first step of the catalytic cycle. Herewith we report a clear correlation between catalyst activity and the DFT-calculated energy difference ΔEi between the active and dormant state. The correlation only holds when the calculations are run on ion pairs, which is less obvious than it may appear because the anion in these systems is not at the catalyst front. This finding provides a comparatively simple and fast method to predict the activity of new catalysts of the same class.
    Macromolecules 01/2012; 45:4046. · 5.93 Impact Factor
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    ABSTRACT: The activity of two bis(phenoxy-amine)ZrR2precatalysts (bis(phenoxy-amine) = N,N0-(3-tBu-5-OMe-2-C6H2OCH2)2-N,N0-Me2-(NCH2CH2N); R = Me (1), Bn(2, benzyl)) toward propene polymerization has been evaluatedusing different activators and cocatalysts: MAO, MAO/TBP, B(C6F5)3/TIBA, and [CPh3][B(C6F5)4]/TIBA (MAO =methylalumoxane, TBP = 2,6-di-tert-butylphenol, TIBA =triisobutylaluminum). It was found that the nature of the activator affects the activity only to a small extent. NMR studies in solution and DFT calculations on the 3a�c and 4a�c (a,MeB(C6F5)3 �; b, BnB(C6F5)3 �; c, B(C6F5)4 �) ion pairs deriving from the activation processes of 1 and 2, respectively, showed that three isomers can form. All of them have the anion in the second coordination sphere, whereas the binding modality of the ligand leads to the mer-mer most stable isomer, fac-mer isomer of intermediate stability, and fac-fac least stable isomer. Notably, the energy of the fac-fac isomer, which is supposed to be the active species in the polymerization process, depends more on the R group and not much on X�, in agreement with the small influence of the activators on the polymerization activity.
    Organometallics 06/2011; 30:3096. · 4.15 Impact Factor
  • Vincenzo Busico, Roberta Cipullo
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    ABSTRACT: In this presentation, some mechanistic aspects of isotactic propene polymerization in the presence of homogeneous Group IV metallocene catalysts are analyzed in the light of new (and still largely unpublished) experimental results. In particular, the regiospecificity of catalyst systems based on two typical C2-symmetric ansazirconocenes (i.e. rac-ethylenebis(1-indenyl) ZrCl2 and rac-dimethylsilylbis(1-indenyl) ZrCl2; co-catalyst, methylalumoxane) is discussed comparatively.An influence of propene concentration on the ratio between 2,1 and 1,3 monomer enchainments and surprisingly - on the stereoregularity of the produced polymers is pointed out. Tentative kinetic explanations of the observed polymerization behaviours are also proposed.
    Macromolecular Symposia 03/2011; 89(1):277 - 287.
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    ABSTRACT: Samples of polypropylene having different stereoregularities, i.e., differing in the isotactic or syndiotactic stereosequence distribution, were separated by means of high-temperature gradient adsorption liquid chromatography. The porous graphite was used as stationary phase in the column packing (Hypercarb®). Predominantly isotactic samples eluted in 1-decanol, while predominantly syndiotactic samples eluted in a binary gradient composed of 1-decanol and 1,2,4-trichlorobenzene. Their elution volumes increased with the average content of the syndiotactic units (racemo dyads mole fraction as determined with the NMR spectroscopy) in the samples. Thus these chromatographic separations represent a new method for the analysis and characterization of stereoregular polyolefins. It requires substantially less time and solvents than the commonly used methods.
    Macromolecular Symposia 01/2011; 298(1):182 - 190.
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    ABSTRACT: Activation parameters for propene polymerization mediated by a bis(phenoxyamine)Zr-dibenzyl catalyst in combination with MAO have been measured experimentally and calculated by DFT; experiment and calculation consistently indicate that the entropic term is the most important reason for the low chain propagation rate with this system. Based on this finding and a review of literature data on a variety of olefin polymerization catalysts, we propose a strong correlation between the propagation rate and how catalysts deal with the entropy loss of monomer capture.
    Journal of the American Chemical Society 10/2010; 132(39):13651-3. · 10.68 Impact Factor
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 03/2010; 41(12).
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    ABSTRACT: The electronic structure of different magnetic states of alpha, beta and gamma modifications of TiCl(3) has been computed employing the density functional theory with periodic boundary conditions and localized Gaussian basis sets. The analysis of the density of the electronic states (DOS) and of the spin density makes it possible to classify these halides as Mott-Hubbard insulators, where the band gap appears a result of large on-site Coulomb interaction. For each crystalline phase, the relative stability of different magnetic states has been analyzed in terms of exchange mechanisms. The electronic population data along with the spin density maps support the assumption of a d(1) Titanium ion in a distorted octahedral crystal field, notwithstanding the not fully ionic character of TiCl(3) modifications. Dispersion forces are particularly important for this material: a classical correction (of the type f(R)/R(6)) has been added to the DFT energies and gradients, providing a good agreement with structural data.
    Physical Chemistry Chemical Physics 12/2009; 11(47):11264-75. · 4.20 Impact Factor
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    ABSTRACT: The electronic structure of different magnetic states of α, β and γ modifications of TiCl3 has been computed employing the density functional theory with periodic boundary conditions and localized Gaussian basis sets. The analysis of the density of the electronic states (DOS) and of the spin density makes it possible to classify these halides as Mott–Hubbard insulators, where the band gap appears a result of large on-site Coulomb interaction. For each crystalline phase, the relative stability of different magnetic states has been analyzed in terms of exchange mechanisms. The electronic population data along with the spin density maps support the assumption of a d1Titanium ion in a distorted octahedral crystal field, notwithstanding the not fully ionic character of TiCl3 modifications. Dispersion forces are particularly important for this material: a classical correction (of the type f(R)/R6) has been added to the DFT energies and gradients, providing a good agreement with structural data.
    Physical Chemistry Chemical Physics 11/2009; 11(47). · 4.20 Impact Factor
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    ABSTRACT: A bis(phenoxy-amine)ZrMe(2) complex (1) was synthesized and activated with B(C(6)F(5))(3) obtaining an ion pair (2) having the MeB(C(6)F(5))(3)(-) counterion in the second coordination sphere as deduced by NMR studies. Both DFT calculations and NMR investigations suggest that the activation is coupled with a change of the binding modality of the tetradentate ligand from cis(N,N)-trans(O,O) in the octahedral dimethyl precursor to 1 cis(N, N)-cis(O,O) in the ion pair 2.
    Dalton Transactions 11/2009; · 4.10 Impact Factor
  • Vincenzo Busico
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    ABSTRACT: The second half of the last Century is often referred to as 'the Age of Plastics'. Whether this calls to one's mind the 1963 Nobel Laureates Karl Ziegler and Giulio Natta, or "The Graduate" Ben Braddock of Charles Webb's novel (played by Dustin Hoffman in a 1967 cult movie) being explained that "the future is in plastics", the conclusion can only be that there is indeed some truth in the definition. But that is over now, and the new Millennium has much more and better to offer than 'plastics'--or not? This perspective article will not address such an epochal question; more modestly, it will make the point that--at odds with a growing misconception--there is still room for good and useful research in metal-catalysed olefin polymerisation for quite some years to come.
    Dalton Transactions 11/2009; · 4.10 Impact Factor
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    ABSTRACT: High-throughput-screening (HTS) tools and methods are used more and more, especially in industry, in the search for new, selective organometallic catalysts. In most cases, the approach is, in essence, empirical, and the strategy is to increase the number of experiments that can be run at a given place in a given time. Highly miniaturized, parallel reaction setups have been implemented for the rapid assessment of whether novel catalysts resulting from the structural amplification of a basic framework are "good" or "bad" with respect to the properties of interest, and, depending on the response, worthy of a subsequent, more-careful evaluation. In this article, we demonstrate that it is possible to utilize these state-of-the-art HTS platforms with a different strategy: the rapid generation of reliable kinetic data for mechanistic studies in view of a thorough understanding and rational catalyst design. Ziegler-Natta-type catalytic olefin polymerization will be used throughout as an example.
    Macromolecular Rapid Communications 10/2009; 30(20):1697-708. · 4.93 Impact Factor

Publication Stats

517 Citations
429.57 Total Impact Points

Institutions

  • 1993–2014
    • University of Naples Federico II
      • • Department of Chemical Sciences
      • • Department of Chemical, Materials and Industrial Production Engineering
      Napoli, Campania, Italy
  • 2009–2013
    • Università degli Studi di Perugia
      • Department of Chemistry
      Perugia, Umbria, Italy
  • 1980
    • Università degli Studi di Napoli L'Orientale
      Napoli, Campania, Italy