Titanocene Complexes Applied in Organic Transformations

Titanium, the second most abundant and one of the cheapest, non-toxic transition metals in the Earth’s crust, is highly favorable for catalytic applications due to its widespread availability, low cost, low toxicity, and well-documented biocompatibility. However, because of its high affinity for oxygen and inherent Lewis acidity, titanium complexes generally exhibit lower tolerance toward various functional groups compared with complexes of later transition metals. The incorporation of cyclopentadienyl ligands significantly enhances the structural tunability of these complexes in their 3D configuration. By modifying the ligand framework, it is possible to fine-tune the Lewis acidity of the central titanium atom as well as the lability and binding characteristics of the ligands. This strategy enables precise control over the catalytic performance of titanocene complexes. The main body of this review provides an overview of recent advances in titanocene catalysis within the field of chemical synthesis since 2019. It includes illustrative examples that demonstrate the substrate scope and practical applications of titanocene catalysts in the synthesis of complex organic molecules and natural products. Finally, the review outlines current research opportunities and strategic directions for future developments in titanocene-based catalysis.