Sandwich Lutetacyclopentadiene with the Coordination of Lithium to the Diene Unit: Synthesis, Structure, and Transformation

The sandwich lutetacyclopentadiene <b>2</b> can be obtained in high yield by the 1:1 reaction of the 1,4-dilithio-1,3-butadiene <b>1</b> with [Cp₂LuCl]. Single-crystal X-ray diffraction of <b>2</b> reveals it as a contact ion pair with the coordination of lithium to the diene unit. This coordination mode is rare in metallacyclopentadiene chemistry. Further transformation of <b>2</b> with the inorganic salt KF and crown ethers leads to the formation of sandwich lutetacyclopentadienes <b>3</b> and <b>5</b> as separated ion pairs and of <b>4</b> as a one-dimensional coordination polymer