Indenyl complexes of Group 9 metals: Synthetic and catalytic chemistry

• A review of indenyl complexes of Group 9 metals is given. • Synthesis and reactivity of indenyl cobalt, rhodium and iridium complexes are described. • Catalytic applications of indenyl complexes are considered. • Recent advances in C H activation and reductive amination catalyzed by indenyl complexes are reviewed. Since their discovery in 1953, indenyl complexes of Group 9 metals have attracted much attention, due to their high performances in many catalytic processes. The indenyl effect, which is expressed in the facilitation of auxiliary ligand substitution as a result of η 5 –η 3 isomerization of indenyl ligand, allows to formation of an addition vacant coordination site. At the same time, this structural flexibility imposes restrictions on the synthesis of indenyl complexes. In the recent years, significant progress has been achieved in the development of their synthetic methods, especially Rh(III) and Ir(III) derivatives, which has triggered new interest in catalytic application of such compounds. The present review starts with a description of the synthesis and reactivity of cobalt, rhodium and iridium complexes bearing indenyl ligand. At the end, their catalytic applications are given. The influence of the ligand environment and the indenyl effect on the catalytic activity is discussed.