Romano Dorta - Independent Researcher (original) (raw)
Papers by Romano Dorta
CCDC 1965291: Experimental Crystal Structure Determination
CCDC 1965293: Experimental Crystal Structure Determination
CCDC 1965294: Experimental Crystal Structure Determination
CCDC 1965296: Experimental Crystal Structure Determination
CCDC 1965292: Experimental Crystal Structure Determination
Springer eBooks, 1999
Chiral bindentate ferrocenyl ligands have been used in a variety of asymmetric catalytic reaction... more Chiral bindentate ferrocenyl ligands have been used in a variety of asymmetric catalytic reactions. Three different recent developments are illustrated here. Firstly, using P, N systems containing a p-acidic phosphine and a bulky pyrazole very high enantioselectivities were obtained in the Pd-catalyzed hydrosilylation of norbornene with trichlorosilane (up to 99% ee). Secondly, selective functionalization of the "lower" Cp ring affords derivatives suited for dendrimer synthesis. Well characterized dendrimers containing up to eight peripheral Josiphos units were used in the Rh-catalyzed hydrogenation of dimethyl itaconate giving eels up to 98.6%. Finally, the enantioselective Ir-catalyzed addition of aniline to norbornene (up to 95% ee), via N-H activation, was achieved using dinuclear Ir(1) complexes as catalyst precursors.
CCDC 1812095: Experimental Crystal Structure Determination
Related Article: Falk W. Seidel, Sibylle Fries, Frank W. Heinemann, Ahmed Chelouan, Andreas Scheu... more Related Article: Falk W. Seidel, Sibylle Fries, Frank W. Heinemann, Ahmed Chelouan, Andreas Scheurer, Alexander Grasruck, Alberto Herrera, Romano Dorta|2018|Organometallics|37|1160|doi:10.1021/acs.organomet.8b00038
Ir(IV) Sulfoxide-Pincer Complexes by Three-Electron Oxidative Additions of Br2 and I2. Unprecedented Trap-Free Reductive Elimination of I2 from a formal d5 Metal
Inorganic Chemistry, Jan 6, 2022
Oxidative addition of 1.5 equiv of bromine or iodine to a Ir(I) sulfoxide pincer complex affords ... more Oxidative addition of 1.5 equiv of bromine or iodine to a Ir(I) sulfoxide pincer complex affords the corresponding Ir(IV) tris-bromido or tris-iodido complexes, respectively. The unprecedented trap-free reductive elimination of iodine from the Ir(IV)-iodido complex is induced by coordination of ligands or donor solvents. In the case of added I-, the isostructural tris-iodo Ir(III)-ate complex is quickly generated, which then can be readily reoxidized to the Ir(IV)-iodido complex with FcPF6 or electrochemically. DFT calculations indicate an "inverted ligand field" in the Ir(IV) complexes and favor dinuclear pathways for the reductive elimination of iodine from the formal d5 metal center.
Evolution of a ‘privileged’ P-alkene ligand: added planar chirality beats BINOL axial chirality in catalytic asymmetric C–C bond formation
Chemical Communications
Planar chirality is introduced in a ‘privileged’ P-alkene phosphoramidite ligand and shown to ove... more Planar chirality is introduced in a ‘privileged’ P-alkene phosphoramidite ligand and shown to overwhelm the chirality of the BINOL auxiliary.
Synlett, 2003
The oxidation of aromatic aldehydes to phenols (Dakin reaction) has been demonstrated to proceed ... more The oxidation of aromatic aldehydes to phenols (Dakin reaction) has been demonstrated to proceed readily on both activated and non-activated aldehydes in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMI][PF 6 ], 1) with high selectivity, easy product separation and excellent chemical yields.
Rhodium complexes with chiral counterions: achiral catalysts in chiral matrices
Journal of Organometallic Chemistry, Feb 1, 2004
... Reacting 12 with N,N,N-trimethyl-1-phenethylammonuim iodide finally led to the desired ammoni... more ... Reacting 12 with N,N,N-trimethyl-1-phenethylammonuim iodide finally led to the desired ammonium phosphine 13 (Eq. (6)) along with precipitated TlI (5). (6). Complexes 12 and 13 were prepared in excellent yields and on gram scales. ...
Organometallics, Nov 16, 2008
to form the corresponding chiral P-alkene ligands 7-12. These ligands were then used to synthesiz... more to form the corresponding chiral P-alkene ligands 7-12. These ligands were then used to synthesize dinuclear chloro-bridged Rh(I) complexes 13-18 with the general formula [Rh(µ-Cl)(P-alkene)] 2. It was shown by X-ray diffraction analyses that these P-alkenes indeed act as bidentate ligands for Rh(I). Furthermore, the crystal structures revealed a change in the hybridization state of the dibenzazepine N atom, passing from sp 2 in the free ligand to sp 3 when coordinated to Rh in a bidentate fashion, thus modifying the bite angle of the ligands. The Rh complexes 16 and 18, bearing the (S)-binaphthol-derived ligand 10 and the R,R-diphenyl-L-prolinol-derived ligand 12, respectively, were shown to be active and enantioselective catalysts for the 1,4 addition of arylboronic acids to enones. At 80°C turnover numbers of up to 61 and enantiomeric excesses of up to 92% were observed.
Iridium-Catalyzed Hydroamination
Wiley-VCH Verlag GmbH & Co. KGaA eBooks, Jul 16, 2009
On the Effect of Iodide and Acids in the Metolachlor Process
Organometallics, Dec 5, 2022
New Ligand Systems Incorporating Two and Three 4,4‘-Bipyridine Units. Characterization of Bi- and Trimetallic Rhodium and Iridium Complexes
Inorganic Chemistry, Sep 29, 2004
The synthesis of new ligand systems based on the bipyridine unit for bi- and trimetallic complexe... more The synthesis of new ligand systems based on the bipyridine unit for bi- and trimetallic complexes, including a rare example of a chiral bimetallic complex, is presented. Ligands BBPX (bis-bipyridine-xylene, 3) and TBPBX (tris-bipyridine-bis-xylene, 4) were prepared in one step by reacting alpha,alpha'-dibromo-o-xylene (2) with 2 equiv of the monolithiated derivative of 4,4'-dimethyl-2,2'-bipyridine. Dilithium (S)-binaphtholate (5) reacted with 2 equiv of 4-bromomethyl-4'-methyl-2,2'-bipyridine (6), affording ligand (S)-BBPBINAP (bis-bipyridine-binaphtholate, 7). These ligands reacted cleanly with 1, 1.5, and 1 equiv of the rhodium dimer [Rh(2)Cl(2)(HD)(2)] (HD = 1,5-hexadiene), respectively. Chloride abstraction led to the isolation of the cationic complexes BBPX[Rh(HD)BF(4)](2) (8), TBPBX[Rh(HD)BF(4)](3) (10), and (S)-BBPBINAP[Rh(HD)BF(4)](2) (12). When BBPX (3), TBPBX (4), and (S)-BBPBINAP (7) were added to 2, 3, and 2 equiv of [Rh(NBD)(2)]BF(4) or [Rh(NBD)(CH(3)CN)(2)]BF(4) (NBD = norbornadiene), respectively, clean formation of BBPX[Rh(NBD)BF(4)](2) (9), TBPBX[Rh(NBD)BF(4)](3) (11), and (S)-BBPBINAP[Rh(NBD)BF(4)](2) (13) was observed. The neutral iridium complex (S)-BBPBINAP[IrCl(COD)](2) (14) was obtained by reaction of (S)-BBPBINAP (7) with 1 equiv of [Ir(2)Cl(2)(COD)(2)] (COD = cyclooctadiene). The complexes were fully characterized including X-ray structural studies of 8, 9, and 13, and preliminary studies on their catalytic activity were performed.
Organometallics, Nov 14, 1998
The observation of an enantiospecific C-H bond activation followed by iodination at an allylic po... more The observation of an enantiospecific C-H bond activation followed by iodination at an allylic position of a coordinated 1,5-COD ligand in a chiral Ir-(I) complex upon addition of I 2 in CH 2 Cl 2 is reported. The same reaction carried out in THF affords an allylic η 3 ,η 2-COD derivative. Both reaction products were characterized by X-ray diffraction.
Synthesis and Characterization of Chiral Bis(aminato)iridate(I) and Aminato-Bridged Iridium(I) Complexes
Helvetica Chimica Acta, Jan 19, 2000
ABSTRACT
Chemistry: A European Journal, Sep 20, 2004
to liberate quantitatively the DMAiminium salt 14. On the other hand, the chiral amine complex (R... more to liberate quantitatively the DMAiminium salt 14. On the other hand, the chiral amine complex (R)-19 formed the optically inactive h 6-bound compound [Ir(cod)(h 6-rac-2 a)]BF 4 (rac-18) upon dissolution in THF at room temperature, presumably via intramolecular C À H activation. This racemization was found to be a two-step event with k' 1 = 9.0 10 À4 s À1 and k 2 = 2.89 10 À5 s À1 , featuring an optically active intermediate prior to sp 3 CÀH activation. Compounds 11, 12, rac-18, and (R)-19 were structurally characterized by single-crystal X-ray analyses.
Catalysts, May 18, 2017
The direct electro-reduction of CO 2 to functional molecules like ethene is a highly desirable va... more The direct electro-reduction of CO 2 to functional molecules like ethene is a highly desirable variant of CO 2 utilization. The formation of, for example, ethene from CO 2 is a multistep electrochemical process going through various intermediates. As these intermediates are organic species, the CO 2 reducing electro-catalyst has to be competent for a variety of organic functional group transformations to yield the final product. In this work, the activity of an in situ-grown nano-structured copper catalyst towards a variety of organic functional group conversions was studied. The model reagents were selected from the product spectrum of actual CO 2 reduction reaction (CO 2 RR) experiments and from proposals in the literature. The CO 2 bulk electrolysis benchmark was conducted at 170 mAcm −2 current density with up to 43% Faradaic Efficiency (FE) for ethene and 23% FE for ethanol simultaneously. To assure relevance for application-oriented conditions, the reactivity screening was conducted at elevated current densities and, thus, overpotentials. The found reactivity pattern was then also transferred to the CO reduction reaction (CORR) under benchmark conditions yielding additional insights. The results suggest that at high current density/high overpotential conditions, also other ethene formation pathways apart from acetaldehyde reduction such as CH 2 dimerization are present. A new suggestion for a high current density mechanism will be presented, which is in agreement with the experimental observations and the found activity pattern of copper cathodes toward organic functional group conversion.
Preparation and Uses of t BuS(O)Cl
Encyclopedia of Reagents for Organic Synthesis, 2021
CCDC 1965291: Experimental Crystal Structure Determination
CCDC 1965293: Experimental Crystal Structure Determination
CCDC 1965294: Experimental Crystal Structure Determination
CCDC 1965296: Experimental Crystal Structure Determination
CCDC 1965292: Experimental Crystal Structure Determination
Springer eBooks, 1999
Chiral bindentate ferrocenyl ligands have been used in a variety of asymmetric catalytic reaction... more Chiral bindentate ferrocenyl ligands have been used in a variety of asymmetric catalytic reactions. Three different recent developments are illustrated here. Firstly, using P, N systems containing a p-acidic phosphine and a bulky pyrazole very high enantioselectivities were obtained in the Pd-catalyzed hydrosilylation of norbornene with trichlorosilane (up to 99% ee). Secondly, selective functionalization of the "lower" Cp ring affords derivatives suited for dendrimer synthesis. Well characterized dendrimers containing up to eight peripheral Josiphos units were used in the Rh-catalyzed hydrogenation of dimethyl itaconate giving eels up to 98.6%. Finally, the enantioselective Ir-catalyzed addition of aniline to norbornene (up to 95% ee), via N-H activation, was achieved using dinuclear Ir(1) complexes as catalyst precursors.
CCDC 1812095: Experimental Crystal Structure Determination
Related Article: Falk W. Seidel, Sibylle Fries, Frank W. Heinemann, Ahmed Chelouan, Andreas Scheu... more Related Article: Falk W. Seidel, Sibylle Fries, Frank W. Heinemann, Ahmed Chelouan, Andreas Scheurer, Alexander Grasruck, Alberto Herrera, Romano Dorta|2018|Organometallics|37|1160|doi:10.1021/acs.organomet.8b00038
Ir(IV) Sulfoxide-Pincer Complexes by Three-Electron Oxidative Additions of Br2 and I2. Unprecedented Trap-Free Reductive Elimination of I2 from a formal d5 Metal
Inorganic Chemistry, Jan 6, 2022
Oxidative addition of 1.5 equiv of bromine or iodine to a Ir(I) sulfoxide pincer complex affords ... more Oxidative addition of 1.5 equiv of bromine or iodine to a Ir(I) sulfoxide pincer complex affords the corresponding Ir(IV) tris-bromido or tris-iodido complexes, respectively. The unprecedented trap-free reductive elimination of iodine from the Ir(IV)-iodido complex is induced by coordination of ligands or donor solvents. In the case of added I-, the isostructural tris-iodo Ir(III)-ate complex is quickly generated, which then can be readily reoxidized to the Ir(IV)-iodido complex with FcPF6 or electrochemically. DFT calculations indicate an "inverted ligand field" in the Ir(IV) complexes and favor dinuclear pathways for the reductive elimination of iodine from the formal d5 metal center.
Evolution of a ‘privileged’ P-alkene ligand: added planar chirality beats BINOL axial chirality in catalytic asymmetric C–C bond formation
Chemical Communications
Planar chirality is introduced in a ‘privileged’ P-alkene phosphoramidite ligand and shown to ove... more Planar chirality is introduced in a ‘privileged’ P-alkene phosphoramidite ligand and shown to overwhelm the chirality of the BINOL auxiliary.
Synlett, 2003
The oxidation of aromatic aldehydes to phenols (Dakin reaction) has been demonstrated to proceed ... more The oxidation of aromatic aldehydes to phenols (Dakin reaction) has been demonstrated to proceed readily on both activated and non-activated aldehydes in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMI][PF 6 ], 1) with high selectivity, easy product separation and excellent chemical yields.
Rhodium complexes with chiral counterions: achiral catalysts in chiral matrices
Journal of Organometallic Chemistry, Feb 1, 2004
... Reacting 12 with N,N,N-trimethyl-1-phenethylammonuim iodide finally led to the desired ammoni... more ... Reacting 12 with N,N,N-trimethyl-1-phenethylammonuim iodide finally led to the desired ammonium phosphine 13 (Eq. (6)) along with precipitated TlI (5). (6). Complexes 12 and 13 were prepared in excellent yields and on gram scales. ...
Organometallics, Nov 16, 2008
to form the corresponding chiral P-alkene ligands 7-12. These ligands were then used to synthesiz... more to form the corresponding chiral P-alkene ligands 7-12. These ligands were then used to synthesize dinuclear chloro-bridged Rh(I) complexes 13-18 with the general formula [Rh(µ-Cl)(P-alkene)] 2. It was shown by X-ray diffraction analyses that these P-alkenes indeed act as bidentate ligands for Rh(I). Furthermore, the crystal structures revealed a change in the hybridization state of the dibenzazepine N atom, passing from sp 2 in the free ligand to sp 3 when coordinated to Rh in a bidentate fashion, thus modifying the bite angle of the ligands. The Rh complexes 16 and 18, bearing the (S)-binaphthol-derived ligand 10 and the R,R-diphenyl-L-prolinol-derived ligand 12, respectively, were shown to be active and enantioselective catalysts for the 1,4 addition of arylboronic acids to enones. At 80°C turnover numbers of up to 61 and enantiomeric excesses of up to 92% were observed.
Iridium-Catalyzed Hydroamination
Wiley-VCH Verlag GmbH & Co. KGaA eBooks, Jul 16, 2009
On the Effect of Iodide and Acids in the Metolachlor Process
Organometallics, Dec 5, 2022
New Ligand Systems Incorporating Two and Three 4,4‘-Bipyridine Units. Characterization of Bi- and Trimetallic Rhodium and Iridium Complexes
Inorganic Chemistry, Sep 29, 2004
The synthesis of new ligand systems based on the bipyridine unit for bi- and trimetallic complexe... more The synthesis of new ligand systems based on the bipyridine unit for bi- and trimetallic complexes, including a rare example of a chiral bimetallic complex, is presented. Ligands BBPX (bis-bipyridine-xylene, 3) and TBPBX (tris-bipyridine-bis-xylene, 4) were prepared in one step by reacting alpha,alpha'-dibromo-o-xylene (2) with 2 equiv of the monolithiated derivative of 4,4'-dimethyl-2,2'-bipyridine. Dilithium (S)-binaphtholate (5) reacted with 2 equiv of 4-bromomethyl-4'-methyl-2,2'-bipyridine (6), affording ligand (S)-BBPBINAP (bis-bipyridine-binaphtholate, 7). These ligands reacted cleanly with 1, 1.5, and 1 equiv of the rhodium dimer [Rh(2)Cl(2)(HD)(2)] (HD = 1,5-hexadiene), respectively. Chloride abstraction led to the isolation of the cationic complexes BBPX[Rh(HD)BF(4)](2) (8), TBPBX[Rh(HD)BF(4)](3) (10), and (S)-BBPBINAP[Rh(HD)BF(4)](2) (12). When BBPX (3), TBPBX (4), and (S)-BBPBINAP (7) were added to 2, 3, and 2 equiv of [Rh(NBD)(2)]BF(4) or [Rh(NBD)(CH(3)CN)(2)]BF(4) (NBD = norbornadiene), respectively, clean formation of BBPX[Rh(NBD)BF(4)](2) (9), TBPBX[Rh(NBD)BF(4)](3) (11), and (S)-BBPBINAP[Rh(NBD)BF(4)](2) (13) was observed. The neutral iridium complex (S)-BBPBINAP[IrCl(COD)](2) (14) was obtained by reaction of (S)-BBPBINAP (7) with 1 equiv of [Ir(2)Cl(2)(COD)(2)] (COD = cyclooctadiene). The complexes were fully characterized including X-ray structural studies of 8, 9, and 13, and preliminary studies on their catalytic activity were performed.
Organometallics, Nov 14, 1998
The observation of an enantiospecific C-H bond activation followed by iodination at an allylic po... more The observation of an enantiospecific C-H bond activation followed by iodination at an allylic position of a coordinated 1,5-COD ligand in a chiral Ir-(I) complex upon addition of I 2 in CH 2 Cl 2 is reported. The same reaction carried out in THF affords an allylic η 3 ,η 2-COD derivative. Both reaction products were characterized by X-ray diffraction.
Synthesis and Characterization of Chiral Bis(aminato)iridate(I) and Aminato-Bridged Iridium(I) Complexes
Helvetica Chimica Acta, Jan 19, 2000
ABSTRACT
Chemistry: A European Journal, Sep 20, 2004
to liberate quantitatively the DMAiminium salt 14. On the other hand, the chiral amine complex (R... more to liberate quantitatively the DMAiminium salt 14. On the other hand, the chiral amine complex (R)-19 formed the optically inactive h 6-bound compound [Ir(cod)(h 6-rac-2 a)]BF 4 (rac-18) upon dissolution in THF at room temperature, presumably via intramolecular C À H activation. This racemization was found to be a two-step event with k' 1 = 9.0 10 À4 s À1 and k 2 = 2.89 10 À5 s À1 , featuring an optically active intermediate prior to sp 3 CÀH activation. Compounds 11, 12, rac-18, and (R)-19 were structurally characterized by single-crystal X-ray analyses.
Catalysts, May 18, 2017
The direct electro-reduction of CO 2 to functional molecules like ethene is a highly desirable va... more The direct electro-reduction of CO 2 to functional molecules like ethene is a highly desirable variant of CO 2 utilization. The formation of, for example, ethene from CO 2 is a multistep electrochemical process going through various intermediates. As these intermediates are organic species, the CO 2 reducing electro-catalyst has to be competent for a variety of organic functional group transformations to yield the final product. In this work, the activity of an in situ-grown nano-structured copper catalyst towards a variety of organic functional group conversions was studied. The model reagents were selected from the product spectrum of actual CO 2 reduction reaction (CO 2 RR) experiments and from proposals in the literature. The CO 2 bulk electrolysis benchmark was conducted at 170 mAcm −2 current density with up to 43% Faradaic Efficiency (FE) for ethene and 23% FE for ethanol simultaneously. To assure relevance for application-oriented conditions, the reactivity screening was conducted at elevated current densities and, thus, overpotentials. The found reactivity pattern was then also transferred to the CO reduction reaction (CORR) under benchmark conditions yielding additional insights. The results suggest that at high current density/high overpotential conditions, also other ethene formation pathways apart from acetaldehyde reduction such as CH 2 dimerization are present. A new suggestion for a high current density mechanism will be presented, which is in agreement with the experimental observations and the found activity pattern of copper cathodes toward organic functional group conversion.
Preparation and Uses of t BuS(O)Cl
Encyclopedia of Reagents for Organic Synthesis, 2021