title: A close look at short C-CH3...potassium contacts: synthetic and theoretical investigations of [M2Co2(mu3-OtBu)2(mu2-OtBu)4(thf)n] (M = Na, K, Rb, thf = tetrahydrofuran).
abstract: Agostic interactions of the type Si-CH3M+ (M = alkali metal) are frequently mentioned in discussions of solid-state structures of trimethylsilyl compounds and the purpose of this work was to elucidate if they also exist in the related tert-butyl species by using density functional theory. The compounds [M2Co2(mu3-OtBu)2(mu2-OtBu)4(thf)n] (M = Na, n = 2; M = K, n = 0; M = Rb, n = 1) have been synthesised and their crystal structures determined. Close contacts of methyl groups with K atoms are observed in the solid-state structure of [K2Co2(mu3-OtBu)2(mu2-OtBu)4], and calculations of the rotational barrier of a tert-butoxy group about the axis through the C-O bond were performed. It was shown that apparent short C-CH3K distances are in this case a consequence of the packing in the extended solid-state structure.
authors.affiliation: Institut für Anorganische Chemie, Universität Karlsruhe TH, Engesserstrasse 15, 76131 Karlsruhe (Germany).
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Anson
authors.forename: Wim
authors.initials: W
authors.lastname: Klopper
authors.forename: Jin-Shan
authors.initials: JS
authors.lastname: Li
authors.forename: Lukasz
authors.initials: L
authors.lastname: Ponikiewski
authors.forename: Alexander
authors.initials: A
authors.lastname: Rothenberger