General Synthesis and Metal Complexes of Fused-Ring Bicyclic Cyclopentadienes

A simple new synthesis of cyclopentadienes possessing fused hydrocarbon (CH2)_n chains is based upon rearrangement of spirolactones. These latter compounds can be made from commercially available oxiranes in a three-step procedure. Cyclopentadienes containing five-and six-membered alkylidene groups, (CH₂)₅ and (CH₂)₆, respectively, in 1,2-positions were thus prepared. They were employed as precursors to generate ligands L for novel neodymium and zirconium complexes of the types L₂ZrCl₂, (L₂NdCl)₂, and L₃Nd. Single-crystal X-ray structures of these complexes are reported.