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

The sandwich lutetacyclopentadiene 2 can be obtained in high yield by the 1:1 reaction of the 1,4-dilithio-1,3-butadiene 1 with [Cp2LuCl]. Single-crystal X-ray diffraction of 2 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 2 with the inorganic salt KF and crown ethers leads to the formation of sandwich lutetacyclopentadienes 3 and 5 as separated ion pairs and of 4 as a one-dimensional coordination polymer.