Heterocycle-fused cyclopentadienyl metal complexes: Heterocene synthesis, structure and catalytic applications

Abstract Metallocenes of the group 4 metals have attracted great attention as precursors of single-site catalysts for the production of advanced polyolefins. The annelation of a cyclopentadienyl ring with a heterocyclic fragment fundamentally changes the electronic and structural characteristics of η5-coordinated ligands and provides new dimensions for the design of novel and effective catalysts. Heterocycle-fused half-sandwich and sandwich metal complexes, called heterocenes, have been extensively studied since the early 2000s. This review describes the different synthetic strategies employed in the preparation of heterocycle-fused η1-η5 and η5-η5 ansa-ligand precursors, and further, discusses the synthesis, molecular structure, and catalytic applications of heterocenes.