Revealing Coordination Patterns in C5-Cyclic Lithium Organics

Lithium cyclopentadienyl derivatives are one of the most applied starting materials in organometallic synthesis. At the same time lithium organics with a C5 perimeter are certainly the most elaborated class of compounds in s-block organometallic chemistry. They are compounds par excellence to generate a huge variety of sandwich or half-sandwich d-block organometallics via transmetalation or salt elimination reactions. The indenyl and fluorenyl substituents contain, apart from the C5 perimeter, either one or two anellated six-membered carbon rings. In addition to the likely η-bonding mode they feature a potential coordination mode from η up to η to the adjacent C6 perimeter (Scheme 1), depending on the Lewis acidity of themetal ion, the donor strength, and steric requirement of the cocoordinating species.