Alkali metal and magnesium enamides from metallation of the alkyl ligands [(2-Pyr)(SiMe3)CH2] and [6-Me-(2-Pyr)(SiMe3)CH2]: a solid state and ab initio studyâ The authors dedicate this paper to the memory of Ron Snaith.Electronic supplementary information (ESI) available: further details of the calculations and structures. See http://www.rsc.org/suppdata/dt/b0/b009596f/
Andrews, Philip C.; Armstrong, David R.; Raston, Colin L.; Roberts, Brett A.; Skelton, Brian W.; White, Allan H.; Andrews Philip C.; Department of Chemistry, Monash University; Armstrong David R.; Department of Pure and Applied Chemistry, University of Strathclyde; Raston Colin L.; Department of Chemistry, Monash University; Roberts Brett A.; Department of Chemistry, Monash University; Skelton Brian W.; Department of Chemistry, University of Western Australia; White Allan H.; Department of Chemistry, University of Western Australia
Журнал:
Dalton Transactions
Дата:
2001
Аннотация:
The alkali metal complexes [rNa·(pmdta)]2, 1, [rK·(pmdta)]2, 2, [rNa·(tmeda)]2, 3, [râ ²Li·(pmdta)], 4, and the magnesium complex, [(r)2Mg·(hmpa)2], 5, formed on metallation of the monosilylated ligands [(2-Pyr)(SiMe3)CH2] (=â rH) and [6-Me-(2-Pyr)(SiMe3)CH2] (=â râ ²H), rather than being metal alkyls, are all metal enamides in the solid state, as evidenced by single crystal X-ray diffraction studies. Even in the presence of the bi- and tri-dentate donors tmeda (=â N,N,Nâ â ²,Nâ â ²-tetramethylethylenediamine) and pmdta (=â N,N,Nâ â ²,Nâ â ²,Nâ â ³-pentamethyldiethylenetriamine) the heavier alkali metal complexes are found to be dimeric. The Li complex is monomeric and adopts the enamide configuration despite the presence of additional steric bulk on introduction of a Me group on the 6-position of the pyridyl ring. This preference for an enamide configuration, rather than that of carbanion or aza-allyl, has been studied by ab initio MO calculations. These confirmed that as the coordination environment of the metal increases the enamide form rather then the aza-allylic form becomes the most energetically favoured configuration.
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