Revealing Coordination Patterns in C5-Cyclic Lithium Organics

Lithium organics with a C-5 perimeter are the most prominent class of compounds in s-block metal organic chemistry to introduce bulky haptotropic bound substituents in organometallic complexes. In this paper we present some coordination patterns. (eta(5)-Cp)Li(PMDETA) (1), (eta(5)-Cp)Li(TMEDA) (2), and (eta(5)-Cp)Li(DME) (3) reveal the electron-releasing capacity of the donor base: The better the density supply from the base, the longer the Li center dot center dot center dot Cp-center distance. The donor base DIGLYME gives the solvent-separated ion pair (SSIP) [(DIGLYME)(2)Li] [(eta(5)-Cp)(2)Li] (4). The contact ion pair (eta(2)-Ind)Li(PMDETA) (5) shows an unprecedented strong C-H center dot center dot center dot pi interaction of a PMDETA methyl group to the center of the C-6 perimeter of an indenyl anion. {(eta(5)-Ind)Li(mu-DME)Li(eta(5)-Ind)} (6) is a unique DME-bridged dimer, while [(DIGLYME)(2)Li] [Ind] (7) crystallizes as a SSIP.