Barbara Milani - Academia.edu (original) (raw)

Papers by Barbara Milani

Research paper thumbnail of Synthesis and Molecular Structures of Nickel(II) and Cobalt(III) Complexes with 2-(Arylimino)-3-(hydroxyimino)butane

European Journal of Inorganic Chemistry, 2003

We report new series of Ni II and Co III complexes with nitrogen-donor chelating ligands of the (... more We report new series of Ni II and Co III complexes with nitrogen-donor chelating ligands of the (E,E)-2-(arylimino)-3-(hydroxyimino)butane type (Ar−N ʝ N−OH). These ligands are characterized by a hydrophilic (OH group) and a hydrophobic region (aryl group). Ni II derivatives were obtained either as trimers of formula [Ni 3 (Ar−N ʝ N−OH) 3 Br 4 (OH)][Br], with the hydrophobic groups oriented on the same side, or as bis(chelated) derivatives with cis geometry, depending on the steric hindrance of the aryl groups. Co III complexes were obtained only as bis(chelated) derivatives, with the two li- [a]

Research paper thumbnail of Palladium complexes with 3-alkyl-substituted-1,10-phenanthrolines: Effect of the remote alkyl substituent on the CO/olefin copolymerization reactions

Organometallics

The coordination chemistry of a series of 3-alkyl-substituted-1,10-phenanthrolines (3-R-phen) to ... more The coordination chemistry of a series of 3-alkyl-substituted-1,10-phenanthrolines (3-R-phen) to palladium as well as the catalytic behavior of the corresponding bischelated derivatives, [Pd(3-R-phen)(2)] [PF(6)](2), in the CO/vinyl arenes copolymerization reaction has been investigated in detail. The alkyl substituents differ in length and steric hindrance. The crystal structure characterization reveals that the two molecules of 3-R-phen are bound to palladium in a syn arrangement with the alkyl groups on the same side of the square planar geometry. In solution a dynamic process involving the equilibrium between syn and anti isomers is evidenced by NMR spectroscopic analysis. This is in agreement with the results of DFT calculations, which indicate similar stabilities for the two isomers. The severe distortions from the ideal square planar coordination geometry observed in the solid state are rationalized, through the DFT analysis, in terms of the HOMO orbitals responsible for the ...

Research paper thumbnail of Synthesis of a sterically modulated pyridine–NHC palladium complex and its reactivity towards ethylene

ABSTRACT A new cationic pyridine-carbene palladium complex has been prepared that features a C,N-... more ABSTRACT A new cationic pyridine-carbene palladium complex has been prepared that features a C,N-bidentate coordinating ligand with a shielded pyridine and a sterically less protected carbene moiety; evaluation of this complex in ethylene polymerization revealed competitive reductive elimination processes and provides guidelines for further catalyst design.

Research paper thumbnail of Trifluoroethanol: key solvent for palladium-catalyzed polymerization reactions

A series of cationic palladium complexes of general formula [Pd(CH 3 )(NCCH 3 )(N-N)][X] (N-N = p... more A series of cationic palladium complexes of general formula [Pd(CH 3 )(NCCH 3 )(N-N)][X] (N-N = phen 1, 3-sec-butyl-1,10-phenanthroline (3-sBu-phen) 2, bpy 3, (À)-(S,S)-3,3 0 -(1,2-dimethylethylenedioxy)-2,2 0 -bipyridine (bbpy) 4, (+)-(R)-3,3 0 -(1-methylethylenedioxy)-2,2 0 -bipyridine (pbpy) 5, N,N 0 -bis(2,6-diisopropylphenyl)-2,3-butanediimine (iso-DAB) 6; X ¼ PF À 6 a, OTf (OTf = triflate) b) containing different nitrogen-donor ligands were prepared from the corresponding neutral chloro derivatives [Pd(CH 3 )(Cl)(N-N)] (1c-6c). They were characterized by 1 H NMR spectroscopy and elemental analysis. Single crystals suitable for X-ray determination were obtained for complexes [Pd(CH 3 )(NCCH 3 )(bbpy)][PF 6 ] (4a), [Pd(CH 3 )(NCCH 3 )(iso-DAB)][PF 6 ] (6a) and [Pd(Cl) 2 (bbpy)] (4c 0 ). The latter is the result of an exchange reaction of the methyl group, present in complex 4c, with a chloride, that occurred after dissolution of 4c in CDCl 3 , for 1 week at 0°C. The catalytic behavior of complexes 1a-5a and 1b-5b in the CO/styrene copolymerization was studied in CH 2 Cl 2 and 2,2,2-trifluoroethanol (TFE) evidencing the positive effect of the fluorinated alcohol both in terms of productivity and molecular weight values of the polymers obtained. Influence of the nitrogen ligand, the anion and the reaction time in both solvents were investigated and is discussed in detail. Encouraging preliminary results were also obtained in the synthesis of polyethylene, in TFE, catalyzed by [Pd(CH 3 )(NCCH 3 )(iso-DAB)][PF 6 ] (6a).

Research paper thumbnail of Hydrogen transfer reduction of polyketones catalyzed by iridium complexes: a novel route towards more biocompatible materials

Dalton transactions (Cambridge, England : 2003), Jan 14, 2008

Transfer hydrogenation from 2-propanol to CO/4-methylstyrene and CO/styrene polyketones was catal... more Transfer hydrogenation from 2-propanol to CO/4-methylstyrene and CO/styrene polyketones was catalyzed by [Ir(diene)(N-N)X] (N-N = nitrogen chelating ligand; X = halogen) in the presence of a basic cocatalyst. The reactions were performed using dioxane as cosolvent, in order to overcome problems due to low polyketone solubility. The polyalcohols were obtained in yields up to 95%, the conversions being markedly dependent on the nature of the ligands coordinated to iridium as well as on the experimental conditions.

Research paper thumbnail of Cationic palladium complexes with mono- and bidentate nitrogen-donor ligands: synthesis, characterization and reactivity in CO/styrene copolymerization reaction

Inorganica Chimica Acta, 2003

Two series of cationic palladium(II) complexes, [Pd(phen)(L)2][PF6]2 (L=pyridine (1a), 2-picoline... more Two series of cationic palladium(II) complexes, [Pd(phen)(L)2][PF6]2 (L=pyridine (1a), 2-picoline (2-pic) (1b), 3-picoline (3-pic) (1c), 4-picoline (4-pic) (1d)) and [Pd(CH3)(L)(phen)][OTf] (L=2-pic (2b), 3-pic (2c) and 4-pic (2d)), with mono and bidentate nitrogen-donor ligands bound to the same metal center have been synthesized and characterized. For the dicationic derivatives the study of the chemical behavior in solution evidences the presence of

Research paper thumbnail of Pd(II) Complexes with Bidentate Nitrogen-Donor Chelating Ligands: Very Versatile and Active Catalyst Precursors for the CO/Olefin Co and Terpolymerization Reactions

Comments on Inorganic Chemistry, 1999

The perfect alternating CO/olefin copolymers constitute an important class of new materials. Thei... more The perfect alternating CO/olefin copolymers constitute an important class of new materials. Their synthesis requires a catalyst; in general, the applied catalytic systems are formed by a palladium(II) salt, modified by diphosphine or dinitrogen chelating ligands, in the presence of a BrØnsted acid as cocatalyst and, frequently, an oxidant such as 1,4-benzoquinone. Alcoholic medium is generally preferred. This overview will

Research paper thumbnail of Highly Efficient Catalytic System for the CO/Styrene Copolymerization:  Toward the Stabilization of the Active Species

Organometallics, 2000

... Milani,* Gianni Corso, and Giovanni Mestroni. Dipartimento di Scienze Chimiche, Università di... more ... Milani,* Gianni Corso, and Giovanni Mestroni. Dipartimento di Scienze Chimiche, Università di Trieste, Via Licio Giorgieri 1, 34127 Trieste, Italy. Carla Carfagna and Mauro Formica. Istituto di Scienze Chimiche, Università di Urbino, P.zza Risorgimento 6, 61029 Urbino, Italy. ...

Research paper thumbnail of Carbonyl Derivatives of Chloride-Dimethyl Sulfoxide-Ruthenium(II) Complexes: Synthesis, Structural Characterization, and Reactivity of Ru(CO)x(DMSO)4-xCl2 Complexes (x = 1-3)

Inorganic Chemistry, 1995

ABSTRACT {{The reactivity of cis- and trans-RuCl2(DMSO)(4) with carbon monoxide has been thorough... more ABSTRACT {{The reactivity of cis- and trans-RuCl2(DMSO)(4) with carbon monoxide has been thoroughly investigated. Depending on the choice of the solvent and the reaction conditions, cis-RuCl2(DMSO)(4) reacts with CO at ambient pressure replacing one, two or three DMSO molecules. The following derivatives have been isolated: trans,cis,cis-Ru-(CO)(DMSO)(DMSO)(2)Cl-2 (1), cis,cis,cis-Ru(CO)(2)(DMSO)(DMSO)Cl-2 (2), cis,trans,cis-Ru(CO)(2)(DMSO)(2)Cl-2 (3) and fac-Ru(CO)(3)(DMSO)Cl-2 (4). Compounds 1, 3 and 4 have been structurally characterized. 1 . 0.5H(2)O: monoclinic, P2(1)/c

Research paper thumbnail of Synthesis and characterization of monochelated carboxylatopalladium(II) complexes with nitrogen-donor chelating ligands. Crystal structures of diacetato(1,10-phenanthroline)- and diacetato(2,9-dimethyl-1,10-phenanthroline)-palladium(II)

Journal of The Chemical Society-dalton Transactions, 1994

... Ligands. Crystal Structures of Diacetato(1 ,lo-phenant hrol ine) - and Diacetato( 2,9-dimethy... more ... Ligands. Crystal Structures of Diacetato(1 ,lo-phenant hrol ine) - and Diacetato( 2,9-dimethyl-1,10-phenanthro1ine)-palladium(ii) t Barbara Milani,8 Enzo Alessio,a Giovanni Mestroni,*n8 Anna Sommazzi,b Fabio Garbassi! Ennio ...

Research paper thumbnail of Palladium Complexes Containing Large Fused Aromatic N−N Ligands as Efficient Catalysts for the CO/Styrene Copolymerization

Organometallics, 2006

... Sheba D. Bergman, † Israel Goldberg, † Carla Carfagna, ‡ Luca Mosca, ‡ Moshe Kol,* † and Barb... more ... Sheba D. Bergman, † Israel Goldberg, † Carla Carfagna, ‡ Luca Mosca, ‡ Moshe Kol,* † and Barbara Milani* §. School ... 2) (a) Benito, JM; de Jesús, E.; da la Mata, FJ; Flores, JC; Gómez, R. Organometallics2006, 25, 3045. ...

Research paper thumbnail of High stereocontrol and efficiency in CO/styrene polyketone synthesis promoted by azabis (oxazoline)-palladium complexes

…, 2006

... Schätz, † Alessandro Scarel, ‡ Ennio Zangrando, ‡ Luca Mosca, § Carla Carfagna, § Anja Gissib... more ... Schätz, † Alessandro Scarel, ‡ Ennio Zangrando, ‡ Luca Mosca, § Carla Carfagna, § Anja Gissibl, † Barbara Milani,* ‡ and Oliver Reiser* †. ... J.; Franchi, D.; Zangrando, E.; Mestroni, G.; Carfagna, C.; Mosca, L.; Seraglia, L.; Consiglio, G.; Milani, B. Chem. Eur. J. 2005, 11, 6014. ...

Research paper thumbnail of Palladium Complexes with 3-Alkyl-Substituted-1,10-Phenanthrolines:  Effect of the Remote Alkyl Substituent on the CO/Olefin Copolymerization Reactions

Organometallics, 2004

The coordination chemistry of a series of 3-alkyl-substituted-1,10-phenanthrolines (3-Rphen) to p... more The coordination chemistry of a series of 3-alkyl-substituted-1,10-phenanthrolines (3-Rphen) to palladium as well as the catalytic behavior of the corresponding bischelated derivatives, [Pd(3-R-phen) 2 ][PF 6 ] 2 , in the CO/vinyl arenes copolymerization reaction has been investigated in detail. The alkyl substituents differ in length and steric hindrance. The crystal structure characterization reveals that the two molecules of 3-R-phen are bound to palladium in a syn arrangement with the alkyl groups on the same side of the square planar geometry. In solution a dynamic process involving the equilibrium between syn and anti isomers is evidenced by NMR spectroscopic analysis. This is in agreement with the results of DFT calculations, which indicate similar stabilities for the two isomers. The severe distortions from the ideal square planar coordination geometry observed in the solid state are rationalized, through the DFT analysis, in terms of the HOMO orbitals responsible for the Pd-N bonds. The [Pd(3-R-phen) 2 ][PF 6 ] 2 complexes efficiently promote the CO/styrene and CO/p-Me-styrene copolymerizations to the corresponding syndiotactic polyketones. Yields and molecular weights show an increasing trend on increasing the steric demand of the R substituent, and the values recorded are the best ones ever reported for copolymerization reactions of this kind in the absence of the oxidant. From the TON numbers this result seems related to an increase of the olefin insertion rate, which proceeds faster when 3-Rphen are used as ligands. A change of the physical nature of the active species, from homogeneous to heterogeneous, occurs during the polymerization process, and the time at which this variation takes place depends on the nature of the olefin. The positive effect of the alkyl substitution is less evident in the CO/ethylene copolymerization. . (1) (a) Fache, F.; Schulz, E.; Tommasino, M. L.; Lemaire, M. Chem.

Research paper thumbnail of Bis(chelated) palladium(II) complexes with a diphosphine and a dinitrogen ligand: very efficient catalyst precursors in the co- and ter-polymerisation of CO and olefins

Journal of the Chemical Society, Dalton Transactions, 1996

... A. Togni, Helv. Chim. Acta, 1995, 78, 883 Article ChemPort ; (h) S. Bartolini, C. Carfagna an... more ... A. Togni, Helv. Chim. Acta, 1995, 78, 883 Article ChemPort ; (h) S. Bartolini, C. Carfagna and A. Musco, Macromol. Rapid Commun., 1995, 16, 9 Article ChemPort ; (i) K. Nozaki, N. Sato and H. Takaya, J. Am. Chem. Soc., 1995 ...

Research paper thumbnail of Facile Synthesis of New, Stable, Palladium-Ethyl Derivatives Containing Nitrogen-Donor Ligands

Organometallics, 2004

The study of insertion reaction of ethylene into the Pd-C bond on complexes of general formula [P... more The study of insertion reaction of ethylene into the Pd-C bond on complexes of general formula [Pd (CH3)(NN) 2][OTf] and [Pd (CH3)(phen)(L)][OTf] led to the development of a facile procedure for the synthesis of new, stable, Pd-ethyl derivatives. The rate of this ...

Research paper thumbnail of Application of Chiral Amine-Imine Ligands in Palladium-Catalyzed Polyketone Synthesis: Effect of Ligand Backbone on the Polymer Stereochemistry

Organometallics, 2009

Two pairs of chiral, enantiomerically pure, amine-imine ligands have been applied to the Pd-catal... more Two pairs of chiral, enantiomerically pure, amine-imine ligands have been applied to the Pd-catalyzed CO/vinyl arene copolymerization reaction. The tacticity of the synthesized polyketones depends on the ligand backbone flexibility: flexible ligands lead to atactic ...

Research paper thumbnail of Counterion Effect on CO/Styrene Copolymerization Catalyzed by Cationic Palladium(II) Organometallic Complexes:  An Interionic Structural and Dynamic Investigation Based on NMR Spectroscopy §

Organometallics, 1999

ABSTRACT Complexes [Pd(η1,η2-C8H12OMe)bipy]+X- (2a−f) (where X = BPh4- (a), CF3SO3- (b), BF4- (c)... more ABSTRACT Complexes [Pd(η1,η2-C8H12OMe)bipy]+X- (2a−f) (where X = BPh4- (a), CF3SO3- (b), BF4- (c), PF6- (d), SbF6- (e), and B(3,5-(CF3)2C6H3)4- (f); bipy = 2,2‘-bipyridine; C8H12OMe = cyclooctenylmethoxy group) were synthesized by the reaction of the dimer [Pd(η1,η2-C8H12OMe)Cl]2 (1) with the bipy ligand in methanol containing Y+X- salts. They were characterized in solution by multinuclear and multidimensional NMR spectroscopy. The solid-state structure of complex 2d was obtained by X-ray single-crystal investigation. The catalytic activity of complexes 2 toward CO/styrene copolymerization in methylene chloride was tested and related to the type of counterion. The order of the catalytic activity of complexes 2a−f is the following: BPh4- CF3SO3- < BF4- < PF6- < SbF6- < B(3,5-(CF3)2C6H3)4-. If the copolymerization reactions are carried out in the presence of an excess of the bipy ligand, the anion effect is less important and the order is the following: BPh4- CF3SO3- < BF4- ≈ B(3,5-(CF3)2C6H3)4- ≈ PF6- ≈ SbF6-. The interionic structure of all complexes was investigated in CD2Cl2 at room and low temperature by 19F{1H} HOESY and 1H NOESY NMR spectroscopies. In solution, the counterions are located above or below the bipy ligand shifted toward the pyridine ring trans to the Pd−C σ bond, while in the crystal structure of 2d, they are settled sideways to the cationic moiety. The best anion in catalysis is the least strong coordinating one that shows the weakest interionic contacts in the 19F{1H} HOESY or 1H NOESY NMR spectra. The dynamic process that exchanges the two pyridyl rings was investigated by variable-temperature NMR spectroscopy in CD2Cl2. The activation parameters were determined. ΔG298 values range from 54 to 58 kJ/mol. The negative values of ΔS (−58/−108 J K-1 mol-1), for all compounds, with the exception of 2f, suggest an associative mechanism.

Research paper thumbnail of Very Stable Palladium(II)−(N−N) Catalysts for the Synthesis of High-Molecular-Weight CO/Styrene Polyketones

Organometallics, 2002

... Dipartimento di Scienze Chimiche, Università degli Studi di Trieste, Via Licio Giorgieri 1, 3... more ... Dipartimento di Scienze Chimiche, Università degli Studi di Trieste, Via Licio Giorgieri 1, 34127 Trieste, Italy. Serafino Gladiali and Rossana Taras. ... Rev.1996, 96, 3435. [ACS Full Text ACS Full Text ]. (b) Mul, WP; Drent, E.; Jansen, PJ; Kramer, AH; Sonnemans, MHW J. Am. ...

Research paper thumbnail of MALDI−TOF Mass Spectrometry in the Study of CO/Aromatic Olefins Terpolymers

Research paper thumbnail of Polymerisation of polar olefins promoted by organometallic cobalt complexes: free radical or coordinative process?

Inorganica Chimica Acta, 2003

Organometallic cobalt(III) complexes, namely [Co(R) 2 (NÃ/N) 2 ][X] (N Ã/N 0/2,2?-bipyridine, 1,1... more Organometallic cobalt(III) complexes, namely [Co(R) 2 (NÃ/N) 2 ][X] (N Ã/N 0/2,2?-bipyridine, 1,10-phenanthroline and 4,7dimethyl-1,10-phenanthroline, R 0/methyl, benzyl; X ( 0/BF 4 ( , PF 6 ( , SbF 6 ( ) have been obtained in good yield as stable orange crystalline compounds, by reduction of CoCl 2 with NaBH 4 in methanol in the presence of N Ã/N and the appropriate organic halide. The crystal structure of the complexes [Co(CH 3 ) 2 (bipy) 2 ][PF 6 ] and [Co(CH 2 Ph) 2 (bipy) 2 ][PF 6 ] shows an octahedral coordination geometry for cobalt with a cis disposition of the two chelating ligands and the organic groups s-bonded to the cobalt atom. In particular, the benzyl derivative shows stacking interactions between the phenyl ring of the benzyl groups and the planar bidentate ligands. NMR investigation confirms the cis coordination geometry in solution. Moreover, in the benzyl derivatives a restricted rotation of the phenyl group around the CÃ/Cipso bond is observed. These complexes efficiently promote the polymerisation of polar olefins, such as acrylonitrile, in the dark and with no addition of radical traps. Molecular weight and polydispersities determination suggest a catalytic controlled radical mechanism. #

Research paper thumbnail of Synthesis and Molecular Structures of Nickel(II) and Cobalt(III) Complexes with 2-(Arylimino)-3-(hydroxyimino)butane

European Journal of Inorganic Chemistry, 2003

We report new series of Ni II and Co III complexes with nitrogen-donor chelating ligands of the (... more We report new series of Ni II and Co III complexes with nitrogen-donor chelating ligands of the (E,E)-2-(arylimino)-3-(hydroxyimino)butane type (Ar−N ʝ N−OH). These ligands are characterized by a hydrophilic (OH group) and a hydrophobic region (aryl group). Ni II derivatives were obtained either as trimers of formula [Ni 3 (Ar−N ʝ N−OH) 3 Br 4 (OH)][Br], with the hydrophobic groups oriented on the same side, or as bis(chelated) derivatives with cis geometry, depending on the steric hindrance of the aryl groups. Co III complexes were obtained only as bis(chelated) derivatives, with the two li- [a]

Research paper thumbnail of Palladium complexes with 3-alkyl-substituted-1,10-phenanthrolines: Effect of the remote alkyl substituent on the CO/olefin copolymerization reactions

Organometallics

The coordination chemistry of a series of 3-alkyl-substituted-1,10-phenanthrolines (3-R-phen) to ... more The coordination chemistry of a series of 3-alkyl-substituted-1,10-phenanthrolines (3-R-phen) to palladium as well as the catalytic behavior of the corresponding bischelated derivatives, [Pd(3-R-phen)(2)] [PF(6)](2), in the CO/vinyl arenes copolymerization reaction has been investigated in detail. The alkyl substituents differ in length and steric hindrance. The crystal structure characterization reveals that the two molecules of 3-R-phen are bound to palladium in a syn arrangement with the alkyl groups on the same side of the square planar geometry. In solution a dynamic process involving the equilibrium between syn and anti isomers is evidenced by NMR spectroscopic analysis. This is in agreement with the results of DFT calculations, which indicate similar stabilities for the two isomers. The severe distortions from the ideal square planar coordination geometry observed in the solid state are rationalized, through the DFT analysis, in terms of the HOMO orbitals responsible for the ...

Research paper thumbnail of Synthesis of a sterically modulated pyridine–NHC palladium complex and its reactivity towards ethylene

ABSTRACT A new cationic pyridine-carbene palladium complex has been prepared that features a C,N-... more ABSTRACT A new cationic pyridine-carbene palladium complex has been prepared that features a C,N-bidentate coordinating ligand with a shielded pyridine and a sterically less protected carbene moiety; evaluation of this complex in ethylene polymerization revealed competitive reductive elimination processes and provides guidelines for further catalyst design.

Research paper thumbnail of Trifluoroethanol: key solvent for palladium-catalyzed polymerization reactions

A series of cationic palladium complexes of general formula [Pd(CH 3 )(NCCH 3 )(N-N)][X] (N-N = p... more A series of cationic palladium complexes of general formula [Pd(CH 3 )(NCCH 3 )(N-N)][X] (N-N = phen 1, 3-sec-butyl-1,10-phenanthroline (3-sBu-phen) 2, bpy 3, (À)-(S,S)-3,3 0 -(1,2-dimethylethylenedioxy)-2,2 0 -bipyridine (bbpy) 4, (+)-(R)-3,3 0 -(1-methylethylenedioxy)-2,2 0 -bipyridine (pbpy) 5, N,N 0 -bis(2,6-diisopropylphenyl)-2,3-butanediimine (iso-DAB) 6; X ¼ PF À 6 a, OTf (OTf = triflate) b) containing different nitrogen-donor ligands were prepared from the corresponding neutral chloro derivatives [Pd(CH 3 )(Cl)(N-N)] (1c-6c). They were characterized by 1 H NMR spectroscopy and elemental analysis. Single crystals suitable for X-ray determination were obtained for complexes [Pd(CH 3 )(NCCH 3 )(bbpy)][PF 6 ] (4a), [Pd(CH 3 )(NCCH 3 )(iso-DAB)][PF 6 ] (6a) and [Pd(Cl) 2 (bbpy)] (4c 0 ). The latter is the result of an exchange reaction of the methyl group, present in complex 4c, with a chloride, that occurred after dissolution of 4c in CDCl 3 , for 1 week at 0°C. The catalytic behavior of complexes 1a-5a and 1b-5b in the CO/styrene copolymerization was studied in CH 2 Cl 2 and 2,2,2-trifluoroethanol (TFE) evidencing the positive effect of the fluorinated alcohol both in terms of productivity and molecular weight values of the polymers obtained. Influence of the nitrogen ligand, the anion and the reaction time in both solvents were investigated and is discussed in detail. Encouraging preliminary results were also obtained in the synthesis of polyethylene, in TFE, catalyzed by [Pd(CH 3 )(NCCH 3 )(iso-DAB)][PF 6 ] (6a).

Research paper thumbnail of Hydrogen transfer reduction of polyketones catalyzed by iridium complexes: a novel route towards more biocompatible materials

Dalton transactions (Cambridge, England : 2003), Jan 14, 2008

Transfer hydrogenation from 2-propanol to CO/4-methylstyrene and CO/styrene polyketones was catal... more Transfer hydrogenation from 2-propanol to CO/4-methylstyrene and CO/styrene polyketones was catalyzed by [Ir(diene)(N-N)X] (N-N = nitrogen chelating ligand; X = halogen) in the presence of a basic cocatalyst. The reactions were performed using dioxane as cosolvent, in order to overcome problems due to low polyketone solubility. The polyalcohols were obtained in yields up to 95%, the conversions being markedly dependent on the nature of the ligands coordinated to iridium as well as on the experimental conditions.

Research paper thumbnail of Cationic palladium complexes with mono- and bidentate nitrogen-donor ligands: synthesis, characterization and reactivity in CO/styrene copolymerization reaction

Inorganica Chimica Acta, 2003

Two series of cationic palladium(II) complexes, [Pd(phen)(L)2][PF6]2 (L=pyridine (1a), 2-picoline... more Two series of cationic palladium(II) complexes, [Pd(phen)(L)2][PF6]2 (L=pyridine (1a), 2-picoline (2-pic) (1b), 3-picoline (3-pic) (1c), 4-picoline (4-pic) (1d)) and [Pd(CH3)(L)(phen)][OTf] (L=2-pic (2b), 3-pic (2c) and 4-pic (2d)), with mono and bidentate nitrogen-donor ligands bound to the same metal center have been synthesized and characterized. For the dicationic derivatives the study of the chemical behavior in solution evidences the presence of

Research paper thumbnail of Pd(II) Complexes with Bidentate Nitrogen-Donor Chelating Ligands: Very Versatile and Active Catalyst Precursors for the CO/Olefin Co and Terpolymerization Reactions

Comments on Inorganic Chemistry, 1999

The perfect alternating CO/olefin copolymers constitute an important class of new materials. Thei... more The perfect alternating CO/olefin copolymers constitute an important class of new materials. Their synthesis requires a catalyst; in general, the applied catalytic systems are formed by a palladium(II) salt, modified by diphosphine or dinitrogen chelating ligands, in the presence of a BrØnsted acid as cocatalyst and, frequently, an oxidant such as 1,4-benzoquinone. Alcoholic medium is generally preferred. This overview will

Research paper thumbnail of Highly Efficient Catalytic System for the CO/Styrene Copolymerization:  Toward the Stabilization of the Active Species

Organometallics, 2000

... Milani,* Gianni Corso, and Giovanni Mestroni. Dipartimento di Scienze Chimiche, Università di... more ... Milani,* Gianni Corso, and Giovanni Mestroni. Dipartimento di Scienze Chimiche, Università di Trieste, Via Licio Giorgieri 1, 34127 Trieste, Italy. Carla Carfagna and Mauro Formica. Istituto di Scienze Chimiche, Università di Urbino, P.zza Risorgimento 6, 61029 Urbino, Italy. ...

Research paper thumbnail of Carbonyl Derivatives of Chloride-Dimethyl Sulfoxide-Ruthenium(II) Complexes: Synthesis, Structural Characterization, and Reactivity of Ru(CO)x(DMSO)4-xCl2 Complexes (x = 1-3)

Inorganic Chemistry, 1995

ABSTRACT {{The reactivity of cis- and trans-RuCl2(DMSO)(4) with carbon monoxide has been thorough... more ABSTRACT {{The reactivity of cis- and trans-RuCl2(DMSO)(4) with carbon monoxide has been thoroughly investigated. Depending on the choice of the solvent and the reaction conditions, cis-RuCl2(DMSO)(4) reacts with CO at ambient pressure replacing one, two or three DMSO molecules. The following derivatives have been isolated: trans,cis,cis-Ru-(CO)(DMSO)(DMSO)(2)Cl-2 (1), cis,cis,cis-Ru(CO)(2)(DMSO)(DMSO)Cl-2 (2), cis,trans,cis-Ru(CO)(2)(DMSO)(2)Cl-2 (3) and fac-Ru(CO)(3)(DMSO)Cl-2 (4). Compounds 1, 3 and 4 have been structurally characterized. 1 . 0.5H(2)O: monoclinic, P2(1)/c

Research paper thumbnail of Synthesis and characterization of monochelated carboxylatopalladium(II) complexes with nitrogen-donor chelating ligands. Crystal structures of diacetato(1,10-phenanthroline)- and diacetato(2,9-dimethyl-1,10-phenanthroline)-palladium(II)

Journal of The Chemical Society-dalton Transactions, 1994

... Ligands. Crystal Structures of Diacetato(1 ,lo-phenant hrol ine) - and Diacetato( 2,9-dimethy... more ... Ligands. Crystal Structures of Diacetato(1 ,lo-phenant hrol ine) - and Diacetato( 2,9-dimethyl-1,10-phenanthro1ine)-palladium(ii) t Barbara Milani,8 Enzo Alessio,a Giovanni Mestroni,*n8 Anna Sommazzi,b Fabio Garbassi! Ennio ...

Research paper thumbnail of Palladium Complexes Containing Large Fused Aromatic N−N Ligands as Efficient Catalysts for the CO/Styrene Copolymerization

Organometallics, 2006

... Sheba D. Bergman, † Israel Goldberg, † Carla Carfagna, ‡ Luca Mosca, ‡ Moshe Kol,* † and Barb... more ... Sheba D. Bergman, † Israel Goldberg, † Carla Carfagna, ‡ Luca Mosca, ‡ Moshe Kol,* † and Barbara Milani* §. School ... 2) (a) Benito, JM; de Jesús, E.; da la Mata, FJ; Flores, JC; Gómez, R. Organometallics2006, 25, 3045. ...

Research paper thumbnail of High stereocontrol and efficiency in CO/styrene polyketone synthesis promoted by azabis (oxazoline)-palladium complexes

…, 2006

... Schätz, † Alessandro Scarel, ‡ Ennio Zangrando, ‡ Luca Mosca, § Carla Carfagna, § Anja Gissib... more ... Schätz, † Alessandro Scarel, ‡ Ennio Zangrando, ‡ Luca Mosca, § Carla Carfagna, § Anja Gissibl, † Barbara Milani,* ‡ and Oliver Reiser* †. ... J.; Franchi, D.; Zangrando, E.; Mestroni, G.; Carfagna, C.; Mosca, L.; Seraglia, L.; Consiglio, G.; Milani, B. Chem. Eur. J. 2005, 11, 6014. ...

Research paper thumbnail of Palladium Complexes with 3-Alkyl-Substituted-1,10-Phenanthrolines:  Effect of the Remote Alkyl Substituent on the CO/Olefin Copolymerization Reactions

Organometallics, 2004

The coordination chemistry of a series of 3-alkyl-substituted-1,10-phenanthrolines (3-Rphen) to p... more The coordination chemistry of a series of 3-alkyl-substituted-1,10-phenanthrolines (3-Rphen) to palladium as well as the catalytic behavior of the corresponding bischelated derivatives, [Pd(3-R-phen) 2 ][PF 6 ] 2 , in the CO/vinyl arenes copolymerization reaction has been investigated in detail. The alkyl substituents differ in length and steric hindrance. The crystal structure characterization reveals that the two molecules of 3-R-phen are bound to palladium in a syn arrangement with the alkyl groups on the same side of the square planar geometry. In solution a dynamic process involving the equilibrium between syn and anti isomers is evidenced by NMR spectroscopic analysis. This is in agreement with the results of DFT calculations, which indicate similar stabilities for the two isomers. The severe distortions from the ideal square planar coordination geometry observed in the solid state are rationalized, through the DFT analysis, in terms of the HOMO orbitals responsible for the Pd-N bonds. The [Pd(3-R-phen) 2 ][PF 6 ] 2 complexes efficiently promote the CO/styrene and CO/p-Me-styrene copolymerizations to the corresponding syndiotactic polyketones. Yields and molecular weights show an increasing trend on increasing the steric demand of the R substituent, and the values recorded are the best ones ever reported for copolymerization reactions of this kind in the absence of the oxidant. From the TON numbers this result seems related to an increase of the olefin insertion rate, which proceeds faster when 3-Rphen are used as ligands. A change of the physical nature of the active species, from homogeneous to heterogeneous, occurs during the polymerization process, and the time at which this variation takes place depends on the nature of the olefin. The positive effect of the alkyl substitution is less evident in the CO/ethylene copolymerization. . (1) (a) Fache, F.; Schulz, E.; Tommasino, M. L.; Lemaire, M. Chem.

Research paper thumbnail of Bis(chelated) palladium(II) complexes with a diphosphine and a dinitrogen ligand: very efficient catalyst precursors in the co- and ter-polymerisation of CO and olefins

Journal of the Chemical Society, Dalton Transactions, 1996

... A. Togni, Helv. Chim. Acta, 1995, 78, 883 Article ChemPort ; (h) S. Bartolini, C. Carfagna an... more ... A. Togni, Helv. Chim. Acta, 1995, 78, 883 Article ChemPort ; (h) S. Bartolini, C. Carfagna and A. Musco, Macromol. Rapid Commun., 1995, 16, 9 Article ChemPort ; (i) K. Nozaki, N. Sato and H. Takaya, J. Am. Chem. Soc., 1995 ...

Research paper thumbnail of Facile Synthesis of New, Stable, Palladium-Ethyl Derivatives Containing Nitrogen-Donor Ligands

Organometallics, 2004

The study of insertion reaction of ethylene into the Pd-C bond on complexes of general formula [P... more The study of insertion reaction of ethylene into the Pd-C bond on complexes of general formula [Pd (CH3)(NN) 2][OTf] and [Pd (CH3)(phen)(L)][OTf] led to the development of a facile procedure for the synthesis of new, stable, Pd-ethyl derivatives. The rate of this ...

Research paper thumbnail of Application of Chiral Amine-Imine Ligands in Palladium-Catalyzed Polyketone Synthesis: Effect of Ligand Backbone on the Polymer Stereochemistry

Organometallics, 2009

Two pairs of chiral, enantiomerically pure, amine-imine ligands have been applied to the Pd-catal... more Two pairs of chiral, enantiomerically pure, amine-imine ligands have been applied to the Pd-catalyzed CO/vinyl arene copolymerization reaction. The tacticity of the synthesized polyketones depends on the ligand backbone flexibility: flexible ligands lead to atactic ...

Research paper thumbnail of Counterion Effect on CO/Styrene Copolymerization Catalyzed by Cationic Palladium(II) Organometallic Complexes:  An Interionic Structural and Dynamic Investigation Based on NMR Spectroscopy §

Organometallics, 1999

ABSTRACT Complexes [Pd(η1,η2-C8H12OMe)bipy]+X- (2a−f) (where X = BPh4- (a), CF3SO3- (b), BF4- (c)... more ABSTRACT Complexes [Pd(η1,η2-C8H12OMe)bipy]+X- (2a−f) (where X = BPh4- (a), CF3SO3- (b), BF4- (c), PF6- (d), SbF6- (e), and B(3,5-(CF3)2C6H3)4- (f); bipy = 2,2‘-bipyridine; C8H12OMe = cyclooctenylmethoxy group) were synthesized by the reaction of the dimer [Pd(η1,η2-C8H12OMe)Cl]2 (1) with the bipy ligand in methanol containing Y+X- salts. They were characterized in solution by multinuclear and multidimensional NMR spectroscopy. The solid-state structure of complex 2d was obtained by X-ray single-crystal investigation. The catalytic activity of complexes 2 toward CO/styrene copolymerization in methylene chloride was tested and related to the type of counterion. The order of the catalytic activity of complexes 2a−f is the following: BPh4- CF3SO3- < BF4- < PF6- < SbF6- < B(3,5-(CF3)2C6H3)4-. If the copolymerization reactions are carried out in the presence of an excess of the bipy ligand, the anion effect is less important and the order is the following: BPh4- CF3SO3- < BF4- ≈ B(3,5-(CF3)2C6H3)4- ≈ PF6- ≈ SbF6-. The interionic structure of all complexes was investigated in CD2Cl2 at room and low temperature by 19F{1H} HOESY and 1H NOESY NMR spectroscopies. In solution, the counterions are located above or below the bipy ligand shifted toward the pyridine ring trans to the Pd−C σ bond, while in the crystal structure of 2d, they are settled sideways to the cationic moiety. The best anion in catalysis is the least strong coordinating one that shows the weakest interionic contacts in the 19F{1H} HOESY or 1H NOESY NMR spectra. The dynamic process that exchanges the two pyridyl rings was investigated by variable-temperature NMR spectroscopy in CD2Cl2. The activation parameters were determined. ΔG298 values range from 54 to 58 kJ/mol. The negative values of ΔS (−58/−108 J K-1 mol-1), for all compounds, with the exception of 2f, suggest an associative mechanism.

Research paper thumbnail of Very Stable Palladium(II)−(N−N) Catalysts for the Synthesis of High-Molecular-Weight CO/Styrene Polyketones

Organometallics, 2002

... Dipartimento di Scienze Chimiche, Università degli Studi di Trieste, Via Licio Giorgieri 1, 3... more ... Dipartimento di Scienze Chimiche, Università degli Studi di Trieste, Via Licio Giorgieri 1, 34127 Trieste, Italy. Serafino Gladiali and Rossana Taras. ... Rev.1996, 96, 3435. [ACS Full Text ACS Full Text ]. (b) Mul, WP; Drent, E.; Jansen, PJ; Kramer, AH; Sonnemans, MHW J. Am. ...

Research paper thumbnail of MALDI−TOF Mass Spectrometry in the Study of CO/Aromatic Olefins Terpolymers

Research paper thumbnail of Polymerisation of polar olefins promoted by organometallic cobalt complexes: free radical or coordinative process?

Inorganica Chimica Acta, 2003

Organometallic cobalt(III) complexes, namely [Co(R) 2 (NÃ/N) 2 ][X] (N Ã/N 0/2,2?-bipyridine, 1,1... more Organometallic cobalt(III) complexes, namely [Co(R) 2 (NÃ/N) 2 ][X] (N Ã/N 0/2,2?-bipyridine, 1,10-phenanthroline and 4,7dimethyl-1,10-phenanthroline, R 0/methyl, benzyl; X ( 0/BF 4 ( , PF 6 ( , SbF 6 ( ) have been obtained in good yield as stable orange crystalline compounds, by reduction of CoCl 2 with NaBH 4 in methanol in the presence of N Ã/N and the appropriate organic halide. The crystal structure of the complexes [Co(CH 3 ) 2 (bipy) 2 ][PF 6 ] and [Co(CH 2 Ph) 2 (bipy) 2 ][PF 6 ] shows an octahedral coordination geometry for cobalt with a cis disposition of the two chelating ligands and the organic groups s-bonded to the cobalt atom. In particular, the benzyl derivative shows stacking interactions between the phenyl ring of the benzyl groups and the planar bidentate ligands. NMR investigation confirms the cis coordination geometry in solution. Moreover, in the benzyl derivatives a restricted rotation of the phenyl group around the CÃ/Cipso bond is observed. These complexes efficiently promote the polymerisation of polar olefins, such as acrylonitrile, in the dark and with no addition of radical traps. Molecular weight and polydispersities determination suggest a catalytic controlled radical mechanism. #