Adriano Berton

Università degli Studi di Palermo, Palermo, Sicily, Italy

Are you Adriano Berton?

Claim your profile

Publications (7)13.66 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The cationic allyl complexes [Pd(η3-2-R1C3H4)(N–N′)]+(N–N′=α-diimine ligand; R1= H or Me) react with BPh4– in the presence of activated olefins to give [Pd(η2-olefin)(N–N′)](olefin = fumaronitrile, dimethyl fumarate or maleic anhydride) and PhCh2C(R1)CH2. The palladium(0) derivatives can be isolated in good yield and have been characterized by elemental analysis, molecular weight measurements and standard spectroscopic techniques. The reaction rates increase with increasing π-accepting ability of the α-diimine, with decreasing steric requirements of the imino carbon substituents and with decreasing stability towards palladium–nitrogen bond breaking in the parent cationic compounds. The rates also increase with decreasing relative permittivity and co-ordinating properties of the solvent. Kinetic measurements in aqueous (2% v/v) methanol provide pseudo-first-order rate constants that are independent of both BPh4– and olefin concentrations. This has been interpreted on the basis of extensive ion pairing between the cationic substrate and the BPh4– anion, followed by rate-determining phenyl transfer to the palladium centre and fast reductive elimination of allylbenzenes.
    No preview · Article · Apr 1991 · ChemInform
  • [Show abstract] [Hide abstract]
    ABSTRACT: The 2-pyridyl complex trans-[PtCl(C5H4N-C2)(PPh3)2] (I) can be prepared in high yield by oxidative addition of 2-chloropyridine to [Pt(PPh3)4]. The reaction of I with 1,2-bis(diphenylphosphino)ethane yields the cis derivative [PtCl(C45H4N-C2)(dppe)] (II). In polar solvents, the latter rearranges to the binuclear cationic complex [Pt(μ-C5H4N-C2, N)(dppe)]2Cl2. The reaction of I with [PdCl(η3-2-MeC3H4)]2 (1/0.5 molar ratio) gives the products [PtCl(μ-C5H4N-C2, N)(PPh3)]2 (IV) and [PdCl(η3-2-MeC3H4)(PPh3)]. 31P NMR monitoring of the reaction suggests that PPh3 transfer occurs in a binuclear platinum/palladium intermediate with a bridging 2-pyridyl ligand, and leads initially to a chloride-bridged species [Pt(μ-Cl)(C5H4-N-C2)(PPh3)]2, which then rearranges to the more stable compound IV. Complexes I and II are readly N-protonated by HCl or HClO4 to give the cationic derivatives [PtCl(C5H5N-C2)(PPh3)2]+ and [PtCl(C5H5N-C2)(dppe)]+. In dichloromethane or 1,2-dichloroethane, the terminal 2-pyridyl group of I and II is slowly N-alkylated by the solvent to give [PtCl{l-R)C5H4n-C2}(PPh3)2]Cl and [PtCl(l-R)C5H4N-C2(dppe)]Cl (R  CH2Cl or CH2CH2Cl).
    No preview · Article · Feb 1989 · Journal of Organometallic Chemistry
  • [Show abstract] [Hide abstract]
    ABSTRACT: Pd(η3-3H5)2 reacts with tetracyanoethylene (TCNE) to give a 1/1 adduct identified as Pd(η3-C3H5)(η1-C3H5)(TCNE) on the basis of spectroscopic evidence and its behaviour in solution. A similar re The complex Pd(η3-C3H5)(η1-C3H5)(TCNE) reacts with triphenylphosphine to give 1,5-hexadiene and Pd(PPh3)2(TCNE); a mechanism for this reaction is pro-posed on the basis of low temperature 1H and 31P NMR spectroscopy study of the soluti during the reaction. The mechanisms are compared with those for the Pt(η3-C3H5) system.
    No preview · Article · Jul 1988 · Journal of Organometallic Chemistry
  • Giacomo Facchin · Roberta Bertani · Adriano Berton · Mario Gleria
    [Show abstract] [Hide abstract]
    ABSTRACT: The Wittig reaction between hexakis(4-formylphenoxy) cyclophosphazene [NP(O-C6H4-p-CHO)2]3 (1) and several stabilized phosphonium ylides leads to the preparation of double bond-containing cyclophosphazenes. All the characterization data obtained for the synthesized compounds indicated that the cyclophosphazene ring is not involved in this reaction, the only reactive functions being the aldehydic groups in the side substituents of 1.These products proved to be promising materials in further functionalization studies and may open interesting perspectives in the case of the corresponding phosphazene high polymers.
    No preview · Article · Jul 1988 · Inorganica Chimica Acta
  • [Show abstract] [Hide abstract]
    ABSTRACT: The imino(2-pyridyl)methylpalladium(II) compound py-2-C(R′)NR (R = C6H4OMe-p, R′ = trans-PdCl(PPh3)2) reacts with [PdCl2(CH2CHPh)]2, [PdCl2- (NCMe)2], and K[PtCl3(CH2CH2)] to give binuclear complexes [MCl2{py-2- C(R′)NR}] (M = Pd, Pt), in which the α-diimino group acts as a chelating bidentate ligand. In hot 1,2-dichloroethane, these complexes undergo a PPh3 and chloride ligand exchange at rates which depend markedly on the metal M (Pd ⪢ Pt), to yield the new derivatives [MCl(PPh3){py-2-C(cis-PdCl2(PPh3))NR}]. The ligand exchange is followed by a much slower decomposition to [MCl2(PPh3)2]. Labile intermediates of the same type, [MCl(PPh3){RNC(cis-PdCl2(PPh3))C(R″)NR}], are formed also in the thermal decomposition of [MCl2{RNC(R′)C(R″)NR}] (R = C6H4OMe-p; R′ = trans-PdCl(PPh3)2; R″ = H, Me). The reactions of the dimethyldithiocarbamate derivative py-2-C(Pd(dmtc)(PPh3))NR (R = C6H4OMe- p) with K[PtCl3(CH2CH2)] and [PdCl2(NCMe)2] yield the different products [PtCl2py-2-C(Pd(dmtc)(PPh3))NR] and [Pd(dmtc)py-2-C(cis-PdCl2(PPh3))NR], respectively.
    No preview · Article · Jul 1988 · Journal of Organometallic Chemistry
  • [Show abstract] [Hide abstract]
    ABSTRACT: The reaction of the binuclear complex [NiCl(μ-2-py)(PPh3)]2 (μ-2-py = μ-C5H4N-C2,N) with the phosphines L (L = PPh3, PMePh2, PMe2Ph or PEt3) or dppe (= 1,2-bis(diphenylphosphino)ethane) in the presence of HClO4 yields the N-protonated 2-pyridyl derivatives trans-[NiCl(2-pyH)(L)2]ClO4 or [NiCl(2-pyH)(dppe)] ClO4 (2-pyH = C5H5N-C2) with a square-planar coordination around the nickel(II) center. These products are largely associated through hydrogen bonding between the NH group and the perchlorate anion, both in the solid and in chlorinated solvents. The configuration in solution has been studied by 1H and 31P NMR spectroscopy. In the complex trans-[NiCl(2-pyH)(PMe2Ph)2]ClO4, the planar 2-pyH ligand is oriented perpendicularly to the coordination plane, with restricted rotation about the NiC2 bond. The reaction of rans-[NiCl(2-pyH)(PMePh2)2]ClO4 with CNC6H4OMe-p and then with NEt3 yields the unstable compound trans-[NiCl{C(2-py)NC6H4OMe-p}(PMePh2)2] through a fast migratory insertion of the isocyanide into the nickel2-pyridyl bond. This product can be isolated and characterized only when the imino(2-pyridyl)methyl group is σ,σ′-N,N′-chelated to ZnCl2.
    No preview · Article · Apr 1987 · Journal of Organometallic Chemistry
  • [Show abstract] [Hide abstract]
    ABSTRACT: The complexes trans-[PdCl(RN)(PPh3)2] (I) [RN = 2-pyridyl (2-Py), 2-pyrazyl (2-pyz), 2-pyrimidyl (2-pym) group] have been prepared in high yield by deprotonation with NEt3 of the corresponding cationic compounds trans[PdCl(RNH) (PPh3)2]+ (RNH = N-protonated C2-heteroaromatic ligand) in the presence of an excess of PPh3. In chlorinated solvents, complexes I undergo a slow reversible dimerization into the binuclear derivatives [PdCl(μ-RN)(PPh3)]2 (II) (μ-RN = C2,N1-bridging ligand). From the 31P NMR spectra in 1,2-dichloroethane the following dissociation constants were obtained: 1.9 mol 1−1 (RN= 2-py), 5.1 × 10−2 (2-pym), 6.6 × 10−3 (2-pyz). The dimerization becomes fast and quantitative if the PPh3, involved in the equilibrium is removed by oxidation or by reaction with [PdCl(η3-2-MeC3H4)]2. Only the 2-pyridyl complex Ia reacts (slowly) with CO yielding the migratory insertion product trans-[PdCl{C(2-py)O}(PPh3)2], together with the dimer IIa. All the complexes I undergo migratory insertion of t-butylisocyanide with formation of trans-[PdCl{C(RN) = NCMe3}(PPh3)2]] at rates which depend on the heterocyclic group (RN = 2-py > 2-pyz ⪢ 2-pym). The reaction of the 2-pyrazyl complex Ib with CNCMe3 has been studied in detail by conductivity measurements and by IR and 31P NMR spectroscopy. The data suggest a complex mechanism in which insertion occurs through rearrangement of a four-coordinate intermediate [PdCl(2-pyz)(CNCMe3)(PPh3)], and through interaction of a cationic intermediate trans-[Pd(2-pyz)(CNCMe3)(PPh3)2]+ (Vb) with Cl− and with the free isocyanide of the initial equilibria. The occurrence of the latter reactions is confirmed by independent experiments in which the cationic complex Vb (isolated as perchlorate salt) is treated with an equimolar amount of [AsPh4]Cl or CNCMe3. The isocyanide-promoted insertion step represents a new mechanistic pathway for isocyanide insertion into the PdC bond of trans-[PdXR(L)2] complexes.
    No preview · Article · Apr 1986 · Journal of Organometallic Chemistry