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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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Dhimba G, Muller A, Lammertsma K. Chiral-at-Metal Racemization Unraveled for MX 2 (a-chel) 2 by means of a Computational Analysis of MoO 2 (acnac) 2. Chemistry 2023; 29:e202302516. [PMID: 37730887 DOI: 10.1002/chem.202302516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 09/13/2023] [Accepted: 09/14/2023] [Indexed: 09/22/2023]
Abstract
Octahedral chiral-at-metal complexes MX2 (a-chel)2 (a-chel=asymmetric chelate) can rearrange their ligands by four mechanisms known as the Bailar (B), Ray-Dutt (RD), Conte-Hippler (CH), and Dhimba-Muller-Lammertsma (DML) twists. Racemization involves their interconnections, which were computed for MoO2 (acnac)2 (acnac=β-ketoiminate) using density functional theory at ωB97x-D with the 6-31G(d,p) and 6-311G(2d,p) basis sets and LANL2DZ for molybdenum. Racemizing the cis(NN) isomer, being the global energy minimum with trans oriented imine groups, is a three step process (DML-CH-DML) that requires 17.4 kcal/mol, while all three cis isomers (cis(NN), cis(NO), and cis(OO)) interconvert at ≤17.9 kcal/mol. The B and RD twists are energetically not competitive and neither are the trans isomers. The interconnection of all enantiomeric minima and transition structures is summarized in a graph that also visualizes valley ridge inflection points for two of the three CH twists. Geometrical features of the minima and twists are given. Lastly, the influence of N-substitution on the favored racemization pathway is evaluated. The present comprehensive study serves as a template for designing chiral-at-metal MX2 (a-chel)2 catalysts that may retain their chiral integrity.
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Affiliation(s)
- George Dhimba
- Department of Chemical Sciences, University of Johannesburg, Auckland Park, Johannesburg, 2006, South Africa
| | - Alfred Muller
- Department of Chemical Sciences, University of Johannesburg, Auckland Park, Johannesburg, 2006, South Africa
| | - Koop Lammertsma
- Department of Chemical Sciences, University of Johannesburg, Auckland Park, Johannesburg, 2006, South Africa
- Department of Chemistry and Pharmaceutical Sciences, Faculty of Sciences Vrije Universiteit Amsterdam, De Boelelaan 1108, 1081 HZ, Amsterdam, The Netherlands
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