Alkali metal cation-pi interactions stabilized solely by [M{N(SiMe3)(2)}(3)](-) anions (M = Mg or Zn): The competing influence of alkali metal center dot center dot center dot C(Me) agostic interactions

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Forbes, G.C. and Kennedy, A.R. and Mulvey, R.E. and Roberts, B.A. and Rowlings, R.B. (2002) Alkali metal cation-pi interactions stabilized solely by [M{N(SiMe3)(2)}(3)](-) anions (M = Mg or Zn): The competing influence of alkali metal center dot center dot center dot C(Me) agostic interactions. Organometallics, 21 (23). pp. 5115-5121. ISSN 0276-7333 (http://dx.doi.org/10.1021/om020596u)

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Abstract

A series of [K(ar)(2)](+) and [Rb(toluene)(3)](+) cations (ar = benzene, toluene, o-xylene, or p-xylene) has been synthesized and crystallized in the presence of [M{N(SiMe3)(2)}(3)](-) anions (M = Mg or Zn). In the solid state all form either extended supermolecular, dimeric or supramolecular, polymeric structures. Only [K(toluene)(2)][Mg{N(SiMe3)(2)}(3)] was found to exist as both suprastructural isomers. Introducing cyclopentadienyl to the system gave a similar zincate with the unusual [K2CP](+) cation. The absence of any traditional Lewis bases facilitates' short metal-to-arene contact distances and makes these species excellent candidates for the study of alkali metal cation-pi interactions. It is shown that K-pi interactions and to a lesser extent Rb-pi interactions are heavily influenced by the number and nature of agostic methyl interactions, especially when the electron-donating ability of these is maximized by adoption of near-linear geometries. These features combine so that the weakest potassium-to-arene interaction observed is that with benzene.

ORCID iDs

Forbes, G.C., Kennedy, A.R. ORCID logoORCID: https://orcid.org/0000-0003-3652-6015, Mulvey, R.E. ORCID logoORCID: https://orcid.org/0000-0002-1015-2564, Roberts, B.A. and Rowlings, R.B.;
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