Lateral Metallation and Redistribution Reactions of Sodium Ferrates Containing Bulky 2,6-Diisopropyl-N-(trimethylsilyl)anilide Ligands |
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Authors: | Dr Lewis C H Maddock Rebekka Morton Dr Alan R Kennedy Prof Dr Eva Hevia |
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Institution: | 1. Department für Chemie, Biochemie und Pharmazie, Universität Bern, Freiestrasse 3, 3012 Bern, Switzerland;2. WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral St, Glasgow, G1 1XL UK |
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Abstract: | Alkali-metal ferrates containing amide groups have emerged as regioselective bases capable of promoting Fe−H exchanges of aromatic substrates. Advancing this area of heterobimetallic chemistry, a new series of sodium ferrates is introduced incorporating the bulky arylsilyl amido ligand N(SiMe3)(Dipp) (Dipp=2,6-iPr2-C6H3). Influenced by the large steric demands imposed by this amide, transamination of NaFe(HMDS)3] (HMDS=N(SiMe3)2) with an excess of HN(SiMe3)(Dipp) led to the isolation of heteroleptic Na(HMDS)2Fe{N(SiMe3)Dipp}]∞ ( 1 ) resulting from the exchange of just one HMDS group. An alternative co-complexation approach, combining the homometallic metal amides NaN(SiMe3)Dipp] and Fe{N(SiMe3)Dipp}2] induces lateral metallation of one Me arm from the SiMe3 group in the iron amide furnishing tetrameric NaFe{N(SiCH2Me2)Dipp}{N(SiMe3)Dipp}]4 ( 2 ). Reactivity studies support that this deprotonation is driven by the steric incompatibility of the single metal amides rather than the basic capability of the sodium reagent. Displaying synergistic reactivity, heteroleptic sodium ferrate 1 can selectively promote ferration of pentafluorobenzene using one of its HMDS arms to give heterotrileptic Na{N(SiMe3)Dipp}(HMDS)Fe(C6F5)]∞ ( 4 ). Attempts to deprotonate less activated pyridine led to the isolation of NaHMDS and heteroleptic Fe(II) amide (py)Fe{N(SiMe3)Dipp}(HMDS)] ( 5 ), resulting from an alternative redistribution process which is favoured by the Lewis donor ability of this substrate. |
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Keywords: | cooperative effects ferrates metallation sodium bimetallic compounds |
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