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Alkali metal-1-azaallyl complexes: X-ray crystallographic, NMR spectroscopic and ab initio calculational studies

Armstrong, D R and Clegg, W and Dunbar, L and Liddle, S T and MacGregor, M and Mulvey, Robert and Reed, D and Quinn, S A (1998) Alkali metal-1-azaallyl complexes: X-ray crystallographic, NMR spectroscopic and ab initio calculational studies. Journal of the Chemical Society, Dalton Transactions (20). pp. 3431-3436. ISSN 0300-9246

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Abstract

A series of alkali metal-1-azaallyl complexes, [{CH3CH2CH2C(H)C(Bu-t)N(H)Li . HMPA}(2)], 1, [{CH3CH2CH2C(H)C(Bu-t)N(H)Na . 2HMPA}(2)] 2 and [{CH2C(Bu-t)N(H)Li . HMPA}(2)] 3, has been synthesised by treating each appropriate metal alkyl reagent (n-butyllithium, n-butylsodium or methyllithium, respectively) with tert-butyl cyanide in the presence of the Lewis base HMPA [hexamethylphosphoramide, (Me2N)(3)P=O]. X-Ray crystallographic studies have established that each structure is dimeric and built around a precisely or approximately centrosymmetric rhomboidal (N-M)(2) ring. However, the nature of the azaallyl-metal bonding differs with 1 and 2 displaying a terminal eta(1)-N arrangement, while 3 displays a chelating eta(3)-NCC arrangement. H-1 and C-13 NMR spectroscopic studies suggest that these distinct bonding modes an retained in [H-2(8)]toluene solution. Long-range ((4)J) "W" coupling (2.4 Hz) is observed for 3 between the NH and one of the alpha-CH2 protons, consistent with the trans orientation of the NH and Cchemical anionC linkages seen in the solid state. The preference for this geometry is confirmed by ab initio MO calculations on models of 3, which examine the energetics of the ketimide-azaallyl isomerism involved in the formation of 1-3.

Item type: Article
ID code: 38190
Keywords: molecular orbital methods, basis sets, aza-allyl, metal, LITHIUM, ions, crystal structures, Chemistry
Subjects: Science > Chemistry
Department: Faculty of Science > Pure and Applied Chemistry
Related URLs:
    Depositing user: Pure Administrator
    Date Deposited: 06 Mar 2012 12:40
    Last modified: 17 Jul 2013 11:42
    URI: http://strathprints.strath.ac.uk/id/eprint/38190

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