Vincenzo Busico

University of Naples Federico II, Napoli, Campania, Italy

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Publications (158)

  • Yue Yu · Vincenzo Busico · Peter H M Budzelaar · [...] · Roberta Cipullo
    [Show abstract] [Hide abstract] ABSTRACT: Quenched-flow studies of MgCl2 -supported Ziegler-Natta catalysts were combined for the first time with (13) C NMR fingerprinting of the nascent polymer and conclusively proved that, depending on the catalyst formulation, propene polymerization can be slowed down significantly by the occurrence of the few regiodefects (2,1 monomer insertions), changing active sites into dormant sites. Catalysts modified with ethylbenzoate show little dormancy. The more industrially relevant phthalate based catalysts, instead, are highly dormant and require the presence of H2 to counteract the deleterious effect of this self-poisoning on productivity and stereoselectivity.
    Article · May 2016 · Angewandte Chemie International Edition
  • [Show abstract] [Hide abstract] ABSTRACT: NMR spectroscopy has been exploited to investigate the reactions of Hf(IV) organometallic complexes with trialkylaluminum and dialkylzinc, with the aim of obtaining insights into the elementary steps of coordinative chain transfer polymerization (CCTP). Bis(cydopentadienyl)hafnium dimethyl (Cp2HfMe2, 1Me(2)) and [N-(2,6-diisopropylphenyl)-alpha-(2-isopropylphenyl)-6-(1-naphthalenyl)-2-pyridinemethanaminato]hafnium dimethyl (2Me(2)) complexes have been chosen as case studies for understanding the differences between poorly performing and highly active CCTP catalysts, in an attempt to assess the effect of the ancillary ligand on the transalkylation rate. 2Me(2) was found to react much more quickly with both AlEt3 and ZnEt2 in comparison to 1Me(2), mainly due to a remarkably lower activation enthalpy. In addition, while the ethylation rate was found to depend on the nature of the alkylating agent for 1Me(2), it does not for 2Me(2). This difference in reactivity was observed also in the case of the ion pairs obtained by reacting 1Me(2) and 2Me(2) with [CPh3][B(C6F5)(4)]. For the latter species, NMR indicated that two main deactivation pathways, namely anion decomposition and a -bond methatesis of Hf-alkyl groups, occur.
    Article · May 2016 · Organometallics
  • Yue Yu · Vincenzo Busico · Peter H. M. Budzelaar · [...] · Roberta Cipullo
    Article · May 2016
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: Herein, we synthesized and characterized through NMR and X-ray techniques a new set of [(NHC)-Au-X] complexes (NHC = 1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene), differing in the counterion X- (X- = OMs-, NO3-, ClO4-, 2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptanoate (PFHp-)). All of these complexes, together with those already known having NTf2- and phthalimide (ptm-) as counterions, were tested as catalysts in the methoxylation of 3-hexyne. The results were analyzed together with those obtained previously. The values of activation parameters (ΔH- and ΔS-) for different anions are also reported. The overall catalytic and kinetic evidence, together with an extensive computational work, confirm the general mechanistic picture given recently in which the anion plays an active role in all steps of the reaction mechanism: pre-equilibrium, nucleophilic attack, and protodeauration. Medium-coordinating anions (OMs-, OTs-) containing a highly symmetric anchoring group give the best catalytic performances. This is due to the following reasons: (a) the pre-equilibrium is shifted toward the outer sphere ion pair, (b) their characteristic basicity promotes the nucleophilic attack, and (c) the possible paths leading to the deactivation of the catalyst are inhibited. These highly symmetric tridentate anions destabilize the unreactive tricoordinated gold species, which instead may be formed by anions with a "planar" anchoring group, such as PFHp- and TFA-. A general trend between coordinating ability and catalytic performances in the alkoxylation of alkynes may be established only when the geometric features of the anion are taken into account. The role of the anion has been also investigated in connection with the nature of the nucleophile. In particular, when the alcohol is a poor nucleophile, a large difference in reactivity is observed, while the use of suitably functionalized alcohols, which may contribute to polarizing the -OH bond through intramolecular interactions, flattens the anion effect.
    Full-text Article · Mar 2016 · Organometallics
  • Merijn Blaakmeer · Giuseppe Antinucci · Vincenzo Busico · [...] · Arno P.M. Kentgens
    [Show abstract] [Hide abstract] ABSTRACT: MgCl2 is a vital component of Ziegler-Natta catalysts for olefin polymerization. Here we synthesized anhydrous MgCl2 using different drying protocols and exploited 1H NMR to quantify the proton content. We report on our study of neat and ball-milled MgCl2 samples by means of 25Mg and 35Cl solid state NMR. DFT calculations of the quadrupole tensor aids in the analysis of the spectra. The results show that, due to the morphology of the neat particles, a preferred orientation is induced which manifests itself in unusual powder line shapes. Ball-milling reduces particle size which subsequently leads to a small distribution of quadrupole parameters for the bulk. Surface sites, highly relevant for catalysis, are not directly observed, due to their broad lines of low intensity.
    Article · Feb 2016 · The Journal of Physical Chemistry C
  • Vincenzo Busico · Roberta Cipullo · Alessio Mingione · Luca Rongo
    [Show abstract] [Hide abstract] ABSTRACT: Despite 60 years of history and a stunning success, Ti-based Ziegler-Natta catalysts for the production of isotactic polypropylene remain ‘black-box’ systems, and progress still relies on trial-and-error. This represents a limitation in a moment when the most widely used industrial systems, containing phthalates as selective modifiers, need to be replaced due to a recent REACH ban. In view of the great complexity of the chemical and physical variables and the heavy non-linearity of their effects, a high/medium-throughput approach to this catalysis is highly desirable; herein we introduce an integrated medium-throughput workflow spanning from propene polymerization to polypropylene microstructural characterization, and combining a 102-fold throughput intensification with equal or higher quality standards compared with conventional methods.
    Article · Feb 2016 · Industrial & Engineering Chemistry Research
  • [Show abstract] [Hide abstract] ABSTRACT: Quenched-flow data for propene polymerization with rac-Me2Si(2-Me-4-Ph-1-indenyl)2ZrCl2/MAO support a picture where removal of MAO qualitatively changes the kinetic profile from a mainly enthalpic to a mainly entropic barrier. DFT studies suggest that a not previously recognized singly-bridged end-on coordination mode of Me6Al2 to catalytically active centers may be kinetically relevant as a resting state. In contrast, the more traditional doubly-bridged complex of Me3Al is proposed to be more relevant to chain transfer to cocatalyst.
    Article · Jan 2016 · Dalton Transactions
  • Roberta Cipullo · Pietro Melone · Yue Yu · [...] · Vincenzo Busico
    [Show abstract] [Hide abstract] ABSTRACT: Despite decades of thorough mechanistic investigations, it is still hard to predict the activity of a novel olefin polymerisation catalyst, even when the precursor is a well-defined molecular entity. In the present study, we highlight the crucial importance of activation entropy on polymerisation rate, and how weak interactions of the catalytic species with electron donating species in the reaction pool can ultimately lower activation free energy.
    Article · May 2015 · Dalton Transactions
  • [Show abstract] [Hide abstract] ABSTRACT: The typical activation of a fourth generation Ziegler-Natta catalyst TiCl4 /MgCl2 /phthalate with triethyl aluminum generates Ti(3+) centers that are investigated by multi-frequency continuous wave and pulse EPR methods. Two families of isolated, molecule-like Ti(3+) species have been identified. A comparison of the experimentally derived g tensors and (35,37) Cl hyperfine and nuclear-quadrupole tensors with DFT-computed values suggests that the dominant EPR-active Ti(3+) species is located on MgCl2 (110) surfaces (or equivalent MgCl2 terminations with tetra-coordinated Mg). O2 reactivity tests show that a fraction of these Ti sites is chemically accessible, an important result in view of the search for the true catalyst active site in olefin polymerization. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Article · Feb 2015 · Angewandte Chemie International Edition in English
  • Christian Ehm · Peter H. M. Budzelaar · Vincenzo Busico
    [Show abstract] [Hide abstract] ABSTRACT: Highly accurate (extrapolated CCSD(T)/aug-cc-pwCVQZ) reference energies have been calculated for olefin insertion in a set of simple models for olefin polymerization catalysts, and also for related reactions (hydrogen transfer to metal and to monomer, allyl formation). The model systems cover early (groups 3 and 4, 10 basic systems, 216 geometries) and late (group 10, 3 basic systems, 51 geometries) transition metals. The reference energies were then used to evaluate the performance of 22 commonly used density functionals, as well as several ab-initio methods. Dispersion corrections (either implicit or explicit) are essential in getting the olefin complexation energy right, but are less important for describing further reactions from the olefin pi-complex stage on. No functional performs entirely satisfactorily (within similar to 1 kcal/mol) for both early and late transition metals. Of the functionals tested, TPSSh-D0 shows the best "across-the-board" performance (important if chemistry involving more than a single metal needs to be described e.g. chain shuttling, bimetallic complexes, bifunctional systems), but M06-2X performs somewhat better specifically for early transition metals. A subsequent benchmark on 21 experimentally known pi-coordination enthalpies and barrier heights for early, middle and late TM systems yielded an MAD of 0.60 kcal/mol using our recommended protocol. Finally, we revisited prototypical catalysts systems studied in early computational work, and conclude that insertion of ethene is nearly barrierless for titanocenes, and has a slightly higher barrier for constrained-geometry catalysts and for Zr analogs.
    Article · Jan 2015 · Journal of Organometallic Chemistry
  • [Show abstract] [Hide abstract] 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.
    Article · Dec 2014 · Journal of Organometallic Chemistry
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    [Show abstract] [Hide abstract] 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.
    Full-text Article · Nov 2014 · Chemistry - A European Journal
  • Roberta Cipullo · Simona Mellino · Vincenzo Busico
    [Show abstract] [Hide abstract] 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.
    Article · Sep 2014 · Macromolecular Chemistry and Physics
  • [Show abstract] [Hide abstract] 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.
    Article · Aug 2014 · Physical Chemistry Chemical Physics
  • Luca Rocchigiani · Vincenzo Busico · Antonello Pastore · [...] · Alceo Macchioni
    [Show abstract] [Hide abstract] 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.
    Article · Feb 2014 · Angewandte Chemie International Edition
  • Source
    Fabio Capone · Luca Rongo · Maddalena D’Amore · [...] · Vincenzo Busico
    [Show abstract] [Hide abstract] 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.
    Full-text Article · Nov 2013 · The Journal of Physical Chemistry C
  • [Show abstract] [Hide abstract] 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.
    Article · Mar 2013 · Dalton Transactions
  • Vincenzo Busico
    [Show abstract] [Hide abstract] 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.
    Article · Mar 2013
  • Vincenzo Busico
    [Show abstract] [Hide abstract] ABSTRACT: This chapter looks back at the fascinating history of isotactic polypropylene, the first man-made stereoregular polymer, from the largely serendipitous discovery to the modern technologies for the industrial production of reactor blends with high-yield Ziegler–Natta catalysts featuring highly controlled morphology. This is also the story of a great man, Giulio Natta, winner of the 1963 Nobel Prize in Chemistry, and his team of incredibly talented young coworkers at the Milan Polytechnic, who in just a few years at the end of the 1950s elucidated the structure of the new polymer and that of the novel TiCl3-based catalysts leading to its formation. The pioneering studies that followed on chain microstructure and the origin of the stereocontrol, and the first educated guesses on the nature of the active species, are critically reviewed, and re-visited with the aid of modern experimental and computational tools and methods, to highlight the current picture of what still represents a most important and lively area of polymer science and organometallic catalysis.
    Chapter · Jan 2013
  • Gianluca Ciancaleoni · Natascia Fraldi · Vincenzo Busico · [...] · Peter H. M. Budzelaar
    [Show abstract] [Hide abstract] 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.
    Article · May 2012 · Macromolecules

Publication Stats

4k Citations

Institutions

  • 1988-2015
    • University of Naples Federico II
      • • Department of Chemical Sciences
      • • Department of Chemical, Materials and Industrial Production Engineering
      Napoli, Campania, Italy
  • 1994-1998
    • Policlinico Federico II di Napoli
      Napoli, Campania, Italy
  • 1980
    • Università degli Studi di Napoli L'Orientale
      Napoli, Campania, Italy
    • Naples Eastern University
      Napoli, Campania, Italy