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Brahma R, Singh AP, Baruah JB. Synthesis and characterization of cis and trans cobalt(II) nalidixate complexes having a 1-(4-chlorophenyl)-3-(pyridin-4-ylmethyl)urea ligand. Dalton Trans 2024. [PMID: 39157957 DOI: 10.1039/d4dt01401d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/20/2024]
Abstract
The synthesis and characterization of specific cis- and trans-isomers of a cobalt(II) bis-nalidixate complex with a pyridine-based urea, 1-(4-chlorophenyl)-3-(pyridin-4-ylmethyl)urea (L), ligand are reported. The two isomers, cis-[Co(L)2(NALD)2]·0.5DMF·H2O and trans-[Co(L)2(NALD)2]·2DMF·2H2O (the nalidixate anion is abbreviated to NALD) were prepared by anion-guided synthesis. When cobalt(II) chloride was used as one of the reactants, the reaction yielded the trans-isomer under ambient reaction conditions. Whereas a reaction using cobalt(II) nitrate provided only the cis-isomer when the reaction was continued for a prolonged time. On the other hand, the cis-isomer was converted to the trans-isomer in solution upon treatment with chloride ions. The chloride-assisted formation of the trans-isomer was investigated by a UV-visible study, and it passed through a bond reorganization by forming a tetrahedral intermediate complex. A DFT calculation was carried out to show the difference in energy between the isomers as well as the energy of a plausible tetrahedral cobalt complex. The aggregation behavior of the cis-isomer in different solvents was investigated, and solvent-dependent aggregation and a solvent-dependent Cotton effect were observed.
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Affiliation(s)
- Rinki Brahma
- Department of Chemistry, Indian Institute of technology Guwahati, Guwahati-781039, Assam, India.
| | - Abhay Pratap Singh
- Department of Chemistry, Indian Institute of technology Guwahati, Guwahati-781039, Assam, India.
| | - Jubaraj Bikash Baruah
- Department of Chemistry, Indian Institute of technology Guwahati, Guwahati-781039, Assam, India.
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Tejero AG, Castillo J, Viguri F, Carmona D, Passarelli V, Lahoz FJ, García-Orduña P, Rodríguez R. Dynamic Configuration on a Chiral-at-Rhodium Catalyst Featuring a Flexible Tetradentate Ligand. Chemistry 2024; 30:e202303935. [PMID: 38031971 DOI: 10.1002/chem.202303935] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Accepted: 11/30/2023] [Indexed: 12/01/2023]
Abstract
The unique dynamic configuration of an enantioselective chiral-at-metal catalyst based on Rh(III) and a non-chiral tetradentate ligand is described and resolved. At room temperature, the catalyst undergoes a dynamic configuration process leading to the formation of two interconvertible metal-stereoisomers, remarkably without racemization. Density functional theory (DFT) calculations indicate that this metal-isomerization proceeds via a concerted transition state, which features a trigonal bipyramidal geometry stabilized by the tetradentate ligand. Furthermore, the resolved enantiopure complex shows high catalytic enantioinduction in the Friedel-Crafts reaction, achieving enantiomeric ratios as high as 99 : 1.
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Affiliation(s)
- Alvaro G Tejero
- Departamento de Catálisis y Procesos Catalíticos, Departamento de Química Inorgánica, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC - Universidad de Zaragoza, Pedro Cerbuna 12, 50009, Zaragoza, Spain
| | - Javier Castillo
- Departamento de Catálisis y Procesos Catalíticos, Departamento de Química Inorgánica, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC - Universidad de Zaragoza, Pedro Cerbuna 12, 50009, Zaragoza, Spain
| | - Fernando Viguri
- Departamento de Catálisis y Procesos Catalíticos, Departamento de Química Inorgánica, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC - Universidad de Zaragoza, Pedro Cerbuna 12, 50009, Zaragoza, Spain
| | - Daniel Carmona
- Departamento de Catálisis y Procesos Catalíticos, Departamento de Química Inorgánica, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC - Universidad de Zaragoza, Pedro Cerbuna 12, 50009, Zaragoza, Spain
| | - Vincenzo Passarelli
- Departamento de Catálisis y Procesos Catalíticos, Departamento de Química Inorgánica, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC - Universidad de Zaragoza, Pedro Cerbuna 12, 50009, Zaragoza, Spain
| | - Fernando J Lahoz
- Departamento de Catálisis y Procesos Catalíticos, Departamento de Química Inorgánica, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC - Universidad de Zaragoza, Pedro Cerbuna 12, 50009, Zaragoza, Spain
| | - Pilar García-Orduña
- Departamento de Catálisis y Procesos Catalíticos, Departamento de Química Inorgánica, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC - Universidad de Zaragoza, Pedro Cerbuna 12, 50009, Zaragoza, Spain
| | - Ricardo Rodríguez
- Departamento de Catálisis y Procesos Catalíticos, Departamento de Química Inorgánica, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC - Universidad de Zaragoza, Pedro Cerbuna 12, 50009, Zaragoza, Spain
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Lastowski RJ, Yarranton JT, Zhu L, Vogiatzis KD, Girolami GS. Three-Center M-H-B Bonds Are Strong Field Interactions. Synthesis and Characterization of M(CH 2NMe 2BH 3) 3 Complexes of Titanium, Chromium, and Cobalt. J Am Chem Soc 2023; 145:23585-23599. [PMID: 37851538 DOI: 10.1021/jacs.3c07336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2023]
Abstract
We describe new compounds of stoichiometry M(CH2NMe2BH3)3 (M = Ti, Cr, and Co), each of which contains three chelating boranatodimethylaminomethyl (BDAM) ligands. In all three compounds, the BDAM anion, which is isoelectronic and isostructural with the neopentyl group, is bound to the metal center at one end by a metal-carbon σ bond and at the other by one three-center M-H-B interaction. The crystal structures show that the d1 titanium(III) compound is trigonal prismatic (or eight-coordinate, if two longer-ranged M···H interactions with the BH3 groups are included), whereas the d3 chromium(III) compound and the d6 cobalt(III) compounds are both fac-octahedral. The Cr and Co compounds exhibit two rapid dynamic processes in solution: exchange between the Δ and Λ enantiomers and exchange of the terminal and bridging hydrogen atoms on boron. For the Co complex, the barrier for Δ/Λ exchange (ΔG⧧298 = 10.1 kcal mol-1) is significantly smaller than those seen in other octahedral cobalt(III) compounds; DFT calculations suggest that Bailar twist and dissociative pathways for Δ/Λ exchange are both possible mechanisms. The UV-vis absorption spectra of the cobalt(III) and chromium(III) species show that the ligand field splittings Δo caused by the M-H-B interactions are unexpectedly large, thus placing them high on the spectrochemical series (near ammonia and alkyl groups); their nephelauxetic effect is also large. The DFT calculations suggest that these properties of M-H-B interactions are in part a consequence of their three-center nature, which delocalizes electron density away from the metal center and reduces electron-electron repulsions.
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Affiliation(s)
- R Joseph Lastowski
- School of Chemical Sciences, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States
| | - Jonathan T Yarranton
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Lingyang Zhu
- School of Chemical Sciences, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States
| | | | - Gregory S Girolami
- School of Chemical Sciences, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States
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Gaydon Q, Bohle DS. Coordination Chemistry of the Parent Dithiocarbamate H 2NCS 2-: Organometallic Chemistry and Tris-Chelates of Group 9 Metals. Inorg Chem 2022; 61:4660-4672. [PMID: 35261230 DOI: 10.1021/acs.inorgchem.1c03789] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Two tris-chelate complexes of cobalt and rhodium and two complexes of Ru(II) of dithiocarbamate, [S2CNH2]-, were synthesized. The complexes were spectroscopically characterized by IR, NMR, UV-vis, and MS and structurally characterized by X-ray diffraction. The structural features of the rhodium complex were compared to those of other tris-chelate Rh(III) dithiocarbamate complexes and are characterized by a change in the ground-state geometry in comparison to expected octahedral tris-chelate complexes. This was confirmed both experimentally by X-ray diffraction and theoretically using DFT calculations. The inversion barriers of Rh(Bz2dtc)3, Ir(Bz2dtc)3, and Rh(Et2dtc)3 were determined using VT-NMR in DMSO. These barriers were found to be surprisingly low for heavy group 9 elements of d6 tris-chelate complexes: values of 16.7, 17.1, and 16.4 kcal/mol were calculated, respectively. By comparing structural features, we are able to determine that the activation barrier for the inversion of stereochemistry of Rh(H2dtc)3 must have a similarly low value. A modified version of the Bailar twist involving an intermediate with C3h geometry was proposed as the mechanism of inversion.
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Affiliation(s)
- Quentin Gaydon
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal H3A 0B8, Quebec, Canada
| | - D Scott Bohle
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal H3A 0B8, Quebec, Canada
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