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Dajnak A, Shi L, Altınbaş Özpınar G, Lenk R, Saffon-Merceron N, Baceiredo A, Kato T, Müller T, Maerten E. Imine-stabilized silylium ions: synthesis, structure and application in catalysis. Dalton Trans 2023; 52:3052-3058. [PMID: 36779626 DOI: 10.1039/d3dt00168g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Novel norbornene-based imine-stabilized silylium ions 2 have been synthesized via the simple reaction of sulfide-stabilized silylium ion 1 with carbonyl derivatives. Those silylium ions were fully characterized in solution and in the solid state by NMR spectroscopy and X-ray diffraction analysis as well as DFT calculations. Unlike the previously reported phosphine-stabilized silylium ion VI, behaving as a Lewis pair, calculations show that 2 have a strong Lewis acid character. Indeed, imine-stabilized silylium ions 2 are able to activate Si-H bonds and catalyzed the hydrosilylation of carbonyl derivatives under mild conditions.
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Affiliation(s)
- Aymeric Dajnak
- Université de Toulouse, UPS, and CNRS, LHFA UMR 5069, 118 route de Narbonne, 31062 Toulouse, France.
| | - Limiao Shi
- Université de Toulouse, UPS, and CNRS, LHFA UMR 5069, 118 route de Narbonne, 31062 Toulouse, France.
| | - Gül Altınbaş Özpınar
- Institute of Chemistry, Carl von Ossietzky University, Oldenburg, D-26129 Oldenburg, Germany
| | - Romaric Lenk
- Université de Toulouse, UPS, and CNRS, LHFA UMR 5069, 118 route de Narbonne, 31062 Toulouse, France.
| | - Nathalie Saffon-Merceron
- Université de Toulouse, UPS, and CNRS, ICT UAR2599, 118 route de Narbonne, 31062 Toulouse, France
| | - Antoine Baceiredo
- Université de Toulouse, UPS, and CNRS, LHFA UMR 5069, 118 route de Narbonne, 31062 Toulouse, France.
| | - Tsuyoshi Kato
- Université de Toulouse, UPS, and CNRS, LHFA UMR 5069, 118 route de Narbonne, 31062 Toulouse, France.
| | - Thomas Müller
- Institute of Chemistry, Carl von Ossietzky University, Oldenburg, D-26129 Oldenburg, Germany
| | - Eddy Maerten
- Université de Toulouse, UPS, and CNRS, LHFA UMR 5069, 118 route de Narbonne, 31062 Toulouse, France.
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Falk A, Bauer JO. Structural and Electronic Effects on Phosphine Chalcogenide Stabilized Silicon Centers in Four-Membered Heterocyclic Cations. Inorg Chem 2022; 61:15576-15588. [PMID: 36130169 DOI: 10.1021/acs.inorgchem.2c02360] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Understanding the interplay of structural and electronic parameters in the stabilization of Lewis acidic silicon centers is crucial for stereochemical questions and applications in bond activation and catalytic transformations. Phosphine chalcogenide functionalized (Ch = O, S, and Se) hydrosilanes having tert-butyl and 2,4,6-trimethoxyphenyl (TMP) substituents on the silicon atom were synthesized, and the ring-closing reactions to afford the heterocyclic four-membered CPChSi cations were investigated. Synthetic access was only achieved for the sulfur- and selenium-based cations. A thorough study by means of single-crystal X-ray structure determination, NMR spectroscopic data, and density functional theory (DFT) calculations provided insight into important electronic and structural parameters affecting the stability of the intramolecularly stabilized cations. Detailed structural considerations were made on the contributions to the ring strain (angular strain and steric repulsion). Thermochemical investigations showed that the substituents on the silicon and phosphorus atoms play an important role for the stability of the cationic heterocycles. In the absence of large steric repulsions through bulky substituents (methyl groups on silicon and tert-butyl groups on phosphorus), an intrinsic stability sequence of the intramolecular Ch-Si coordination depending on the chalcogen atom in the direction Se ≤ S < O can be observed. However, the order is reversed (O < S < Se) in the case of strong repulsions between sterically demanding substituents (tert-butyl groups on both silicon and phosphorus atoms). Natural bond orbital (NBO) analysis supported the explanations for the observed deshielding trends in 31P NMR spectroscopy and revealed that the O-Si bond is more ionic in nature compared to the S-Si and Se-Si bonds, with the latter exhibiting higher covalent character due to a more efficient charge transfer through a σ-type nCh → pSi interaction.
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Affiliation(s)
- Alexander Falk
- Institut für Anorganische Chemie, Fakultät für Chemie und Pharmazie, Universität Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany
| | - Jonathan O Bauer
- Institut für Anorganische Chemie, Fakultät für Chemie und Pharmazie, Universität Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany
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