A Close Look at Short C-CH_3...Potassium Contacts:Synthetic and Theoretical Investigations of [M_2CO_2(mu_3-OtBu)_2(mu_2-OtBu)_4(thf)_n(M = Na,K,Rb,thf=tetrahydrofuran)

摘要

Agostic interactions of the type Si-CH_3...M~+(M = alkali metal)are frequently mentioned in discussions of solid-state structures of trimethyl-silyl 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 [M_2Co(mu_3-OtBu)_2(mu_2-OtBu)_4(thf)_n](M = Na,n = 2;M = K,n = 0;M = Rb,n = 1)have been syn-thesised and their crystal structures determined.Close contacts of methyl groups with K atoms are observed in the solid-state structure of [K_2CO_2(mu_3-OtBu)_2(mu_2-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-CH_3...K distances are in this case a consequence of the packing in the extended solid-state structure.