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Papers by walter baratta

European Journal of Inorganic Chemistry, Jan 29, 2014

A cationic phthalimido-functionalized N-heterocyclic carbene (NHC) palladium(II) complex has been... more A cationic phthalimido-functionalized N-heterocyclic carbene (NHC) palladium(II) complex has been synthesized from [3-methyl-1-(2Ј-phthalimidoethyl)imidazolium] hexafluorophosphate ([NHC Me,Pht H]PF 6) by transmetalation and isolated in 67 % yield. The title complex has been applied as [a] Molecular Catalysis,

European Journal of Inorganic Chemistry, Dec 2, 2015

Two novel di(N-heterocyclic carbene) complexes of formula (μ-PyrIm-CH 2-ImPyr)[IrCp*Cl] 2 (PF 6) ... more Two novel di(N-heterocyclic carbene) complexes of formula (μ-PyrIm-CH 2-ImPyr)[IrCp*Cl] 2 (PF 6) 2 (1) and μ-MeIm-CH 2 (p-C 6 H 2)CH 2-ImMe[IrCp*Cl] 2 (2) (Im = imidazol-2-ylidene) have been synthesised by transmetallation of the dicarbene ligand from the corresponding dicarbene silver complex, using [IrCp*(μ-Cl)Cl] 2 as an iridium precursor. The structure of com-[a]

Acta Crystallographica Section A, Aug 23, 2005

The coordination of inert C-H bonds to a transition metal center is of fundamental interest for s... more The coordination of inert C-H bonds to a transition metal center is of fundamental interest for stoichiometric and catalytic reactions, with particular regard to the problem of alkane functionalization via C-H bond activation. Unfortunately, information on the nature of the primary adduct is still very scarce, since saturated hydrocarbons are notoriously very poor ligands. By use of the phosphine PR 2 (2,6-Me 2 C 6 H 3) (R = Ph, Cy), bearing two methyl groups in the ortho position, rare examples of 14-electron Ru(II) and Pt(II) complexes have been isolated [1]. Solid state studies, using both X-ray and neutron diffraction techniques, reveal that nonclassical M••• 3-H 2 C agostic interactions take place and this result is in agreement with a structural survey on Cambridge databank, data in solution and a computational analysis. The reactivity of these complexes is reported, as well as the use of the Ru system as precursor for the preparation of highly active transfer hydrogenation catalysts.

Acta Crystallographica Section A, Aug 23, 2005

different electronic and structural effects when compared with the analogues. Very little has bee... more different electronic and structural effects when compared with the analogues. Very little has been done on poly(pyrazolyl)borate systems bearing electron withdrawing substituents. The electron withdrawing groups in polyfluorinated ligands commonly improve the volatility, oxidation resistance, thermal stability, and solubility of metal complexes. To our knowledge, no poly(azolyl)borates containing a-NO 2 function have been prepared, presumably due to difficulties in the synthesis of ligands having both a hydride and a nitro group. However, a poly(azolyl)borate containing a-NO 2 substituent could be of interest due to its high coordinative flexibility from 4-to µ 4-N 2 O 2 coordination ability. We report here on the syntheses and structural investigations of main-group metal elements Ca, Ba and Sr with the hydrotris(3methylpyrazolyl)borate, the hydrotris(1,2,4-triazolyl)borate and the new hydrotris(3-nitro-1,2,4-triazolyl)borate, an emerging category of electron withdrawing substituted scorpionate ligands.

Inorganics (Basel), Apr 22, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Journal of Organometallic Chemistry, Aug 1, 1997

ABSTRACT

Coordination Chemistry Reviews, Oct 1, 2019

Hydration and alkoxylation of alkynes are key processes for the industrial production of carbonyl... more Hydration and alkoxylation of alkynes are key processes for the industrial production of carbonyl derivatives. In this review, the pivotal role of ion pairing in the mechanism of hydration and alkoxylation of alkynes promoted by gold(I) catalysts L-Au-X is deeply analyzed and discussed, that has been elucidated by means of experimental findings supported by some theoretical calculations. In particular, the crucial role of the counterion X À is fully described in chapter 2. The catalytic performances in the alkoxylation and hydration of alkynes promoted by gold(I) are influenced by the coordination ability and basicity (proton affinity) of the counterion (paragraph 2.3) and the anion/cation relative orientation (paragraph 2.3). Also the appropriate matching of X À and the neutral ligand L must be taken into account to improve the catalytic performance of gold catalysts (paragraph 2.4). A survey of other non-covalent interactions, which however play a kinetic important role (hydrogen bonds, those triggered by suitable functionalities present on the ligand L, formation of supramolecular catalytic systems or micelles, and others), is presented in chapter 3. The progress in the development of sustainable methodologies for the gold(I)-promoted hydration of alkynes is discussed in chapter 4. In particular, paragraph 4.1 focuses on the unique role played by the anion in the L-Au-X catalyzed hydration of alkynes conducted in solvent-, silver-, and acid-free conditions. To conclude this critical review, in paragraph 4.2 it is highlighted how the amount of ion pairing, combined with the presence of suitable functionalities in neoteric solvent, may allow the development of green protocols for gold(I) catalyzed hydration of alkynes.

ChemInform, Nov 1, 2016

Three Ru(II) and two Os(II) CNN pincer complexes are synthesized and tested in the title reaction.

ChemInform, Dec 19, 2000

ABSTRACT

Gazzetta Chimica Italiana, 1990

Chemcatchem, Sep 21, 2016

Aldehydes are chemoselectively reduced to primary alcohols using HCOONH4 as hydrogen donor, via t... more Aldehydes are chemoselectively reduced to primary alcohols using HCOONH4 as hydrogen donor, via transfer hydrogenation catalyzed by benzo[h]quinoline pincer complexes RuCl(CNN Ph)(PP) at S/C = 2000-20000. This practical reaction performed with aldehydes of commercial grade purity in a water / toluene biphasic system affords alcohols without formation of condensation or amination side products.

Catalysis Science & Technology

The neutral ruthenium cyclometalated complexes [Ru(C^N)(η2-OAc)(dppb)] proven to be efficient cat... more The neutral ruthenium cyclometalated complexes [Ru(C^N)(η2-OAc)(dppb)] proven to be efficient catalysts in Oppenauer-type oxidation and transfer hydrogenation reactions with TOF up to 14 300 h−1 and show cytotoxic activity against U87 cancer cells.

European Journal of Inorganic Chemistry

Chemistry – A European Journal

Chemistry – A European Journal

The chiral cationic complex [Ru(η 1-OAc)(CO)((R,R)-Skewphos)(phen)]OAc (2 R), isolated from react... more The chiral cationic complex [Ru(η 1-OAc)(CO)((R,R)-Skewphos)(phen)]OAc (2 R), isolated from reaction of [Ru(η 1-OAc)(η 2-OAc)(R,R)-Skewphos)(CO)] (1 R) with phen, reacts with NaOPiv and KSAc affording [RuX(CO)((R,R)-Skewphos)(phen)]Y (X = Y = OPiv 3 R ; X = SAc, Y = OAc 4 R). The corresponding enantiomers 2 S-4 S have been obtained from 1 S containing (S,S)-Skewphos. Reaction of 2 R and 2 S with (S)-cysteine and NaPF 6 at pH = 9 gives the diastereoisomers [Ru((S)-Cys)(CO)(PP)(phen)]PF 6 (PP = (R,R)-Skewphos 2 R-Cys; (S,S)-Skewphos 2 S-Cys). The DFT energetic profile for 2 R with (S)cysteine in H 2 O indicates that aquo and hydroxo species are involved in formation of 2 R-Cys. The stability of the ruthenium complexes in 0.9 % w/v NaCl solution, PBS and complete DMEM medium, as well as their n-octanol/water partition coefficient (logP), have been evaluated. The chiral complexes show high cytotoxic activity against SW1736, 8505 C, HCT-116 and A549 cell lines with EC 50 values of 2.8-0.04 μM. The (R,R)-Skewphos derivatives show higher cytotoxicity compared to their enantiomers, 4 R (EC 50 = 0.04 μM) being 14 times more cytotoxic than 4 S against the anaplastic thyroid cancer 8505 C cell line.

European Journal of Inorganic Chemistry, Jan 29, 2014

A cationic phthalimido-functionalized N-heterocyclic carbene (NHC) palladium(II) complex has been... more A cationic phthalimido-functionalized N-heterocyclic carbene (NHC) palladium(II) complex has been synthesized from [3-methyl-1-(2Ј-phthalimidoethyl)imidazolium] hexafluorophosphate ([NHC Me,Pht H]PF 6) by transmetalation and isolated in 67 % yield. The title complex has been applied as [a] Molecular Catalysis,

European Journal of Inorganic Chemistry, Dec 2, 2015

Two novel di(N-heterocyclic carbene) complexes of formula (μ-PyrIm-CH 2-ImPyr)[IrCp*Cl] 2 (PF 6) ... more Two novel di(N-heterocyclic carbene) complexes of formula (μ-PyrIm-CH 2-ImPyr)[IrCp*Cl] 2 (PF 6) 2 (1) and μ-MeIm-CH 2 (p-C 6 H 2)CH 2-ImMe[IrCp*Cl] 2 (2) (Im = imidazol-2-ylidene) have been synthesised by transmetallation of the dicarbene ligand from the corresponding dicarbene silver complex, using [IrCp*(μ-Cl)Cl] 2 as an iridium precursor. The structure of com-[a]

Acta Crystallographica Section A, Aug 23, 2005

The coordination of inert C-H bonds to a transition metal center is of fundamental interest for s... more The coordination of inert C-H bonds to a transition metal center is of fundamental interest for stoichiometric and catalytic reactions, with particular regard to the problem of alkane functionalization via C-H bond activation. Unfortunately, information on the nature of the primary adduct is still very scarce, since saturated hydrocarbons are notoriously very poor ligands. By use of the phosphine PR 2 (2,6-Me 2 C 6 H 3) (R = Ph, Cy), bearing two methyl groups in the ortho position, rare examples of 14-electron Ru(II) and Pt(II) complexes have been isolated [1]. Solid state studies, using both X-ray and neutron diffraction techniques, reveal that nonclassical M••• 3-H 2 C agostic interactions take place and this result is in agreement with a structural survey on Cambridge databank, data in solution and a computational analysis. The reactivity of these complexes is reported, as well as the use of the Ru system as precursor for the preparation of highly active transfer hydrogenation catalysts.

Acta Crystallographica Section A, Aug 23, 2005

different electronic and structural effects when compared with the analogues. Very little has bee... more different electronic and structural effects when compared with the analogues. Very little has been done on poly(pyrazolyl)borate systems bearing electron withdrawing substituents. The electron withdrawing groups in polyfluorinated ligands commonly improve the volatility, oxidation resistance, thermal stability, and solubility of metal complexes. To our knowledge, no poly(azolyl)borates containing a-NO 2 function have been prepared, presumably due to difficulties in the synthesis of ligands having both a hydride and a nitro group. However, a poly(azolyl)borate containing a-NO 2 substituent could be of interest due to its high coordinative flexibility from 4-to µ 4-N 2 O 2 coordination ability. We report here on the syntheses and structural investigations of main-group metal elements Ca, Ba and Sr with the hydrotris(3methylpyrazolyl)borate, the hydrotris(1,2,4-triazolyl)borate and the new hydrotris(3-nitro-1,2,4-triazolyl)borate, an emerging category of electron withdrawing substituted scorpionate ligands.

Inorganics (Basel), Apr 22, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Journal of Organometallic Chemistry, Aug 1, 1997

ABSTRACT

Coordination Chemistry Reviews, Oct 1, 2019

Hydration and alkoxylation of alkynes are key processes for the industrial production of carbonyl... more Hydration and alkoxylation of alkynes are key processes for the industrial production of carbonyl derivatives. In this review, the pivotal role of ion pairing in the mechanism of hydration and alkoxylation of alkynes promoted by gold(I) catalysts L-Au-X is deeply analyzed and discussed, that has been elucidated by means of experimental findings supported by some theoretical calculations. In particular, the crucial role of the counterion X À is fully described in chapter 2. The catalytic performances in the alkoxylation and hydration of alkynes promoted by gold(I) are influenced by the coordination ability and basicity (proton affinity) of the counterion (paragraph 2.3) and the anion/cation relative orientation (paragraph 2.3). Also the appropriate matching of X À and the neutral ligand L must be taken into account to improve the catalytic performance of gold catalysts (paragraph 2.4). A survey of other non-covalent interactions, which however play a kinetic important role (hydrogen bonds, those triggered by suitable functionalities present on the ligand L, formation of supramolecular catalytic systems or micelles, and others), is presented in chapter 3. The progress in the development of sustainable methodologies for the gold(I)-promoted hydration of alkynes is discussed in chapter 4. In particular, paragraph 4.1 focuses on the unique role played by the anion in the L-Au-X catalyzed hydration of alkynes conducted in solvent-, silver-, and acid-free conditions. To conclude this critical review, in paragraph 4.2 it is highlighted how the amount of ion pairing, combined with the presence of suitable functionalities in neoteric solvent, may allow the development of green protocols for gold(I) catalyzed hydration of alkynes.

ChemInform, Nov 1, 2016

Three Ru(II) and two Os(II) CNN pincer complexes are synthesized and tested in the title reaction.

ChemInform, Dec 19, 2000

ABSTRACT

Gazzetta Chimica Italiana, 1990

Chemcatchem, Sep 21, 2016

Aldehydes are chemoselectively reduced to primary alcohols using HCOONH4 as hydrogen donor, via t... more Aldehydes are chemoselectively reduced to primary alcohols using HCOONH4 as hydrogen donor, via transfer hydrogenation catalyzed by benzo[h]quinoline pincer complexes RuCl(CNN Ph)(PP) at S/C = 2000-20000. This practical reaction performed with aldehydes of commercial grade purity in a water / toluene biphasic system affords alcohols without formation of condensation or amination side products.

Catalysis Science & Technology

The neutral ruthenium cyclometalated complexes [Ru(C^N)(η2-OAc)(dppb)] proven to be efficient cat... more The neutral ruthenium cyclometalated complexes [Ru(C^N)(η2-OAc)(dppb)] proven to be efficient catalysts in Oppenauer-type oxidation and transfer hydrogenation reactions with TOF up to 14 300 h−1 and show cytotoxic activity against U87 cancer cells.

European Journal of Inorganic Chemistry

Chemistry – A European Journal

Chemistry – A European Journal

The chiral cationic complex [Ru(η 1-OAc)(CO)((R,R)-Skewphos)(phen)]OAc (2 R), isolated from react... more The chiral cationic complex [Ru(η 1-OAc)(CO)((R,R)-Skewphos)(phen)]OAc (2 R), isolated from reaction of [Ru(η 1-OAc)(η 2-OAc)(R,R)-Skewphos)(CO)] (1 R) with phen, reacts with NaOPiv and KSAc affording [RuX(CO)((R,R)-Skewphos)(phen)]Y (X = Y = OPiv 3 R ; X = SAc, Y = OAc 4 R). The corresponding enantiomers 2 S-4 S have been obtained from 1 S containing (S,S)-Skewphos. Reaction of 2 R and 2 S with (S)-cysteine and NaPF 6 at pH = 9 gives the diastereoisomers [Ru((S)-Cys)(CO)(PP)(phen)]PF 6 (PP = (R,R)-Skewphos 2 R-Cys; (S,S)-Skewphos 2 S-Cys). The DFT energetic profile for 2 R with (S)cysteine in H 2 O indicates that aquo and hydroxo species are involved in formation of 2 R-Cys. The stability of the ruthenium complexes in 0.9 % w/v NaCl solution, PBS and complete DMEM medium, as well as their n-octanol/water partition coefficient (logP), have been evaluated. The chiral complexes show high cytotoxic activity against SW1736, 8505 C, HCT-116 and A549 cell lines with EC 50 values of 2.8-0.04 μM. The (R,R)-Skewphos derivatives show higher cytotoxicity compared to their enantiomers, 4 R (EC 50 = 0.04 μM) being 14 times more cytotoxic than 4 S against the anaplastic thyroid cancer 8505 C cell line.