Trimethylsilyl-functionalised bis(indenyl)iron(II) complexes: solid-state structure of [η5-1,3-(SiMe3)2C9H5]2Fe

The synthesis of the bis(η5-indenyl)iron sandwich complexes (η5-1-SiMe3–C9H6)2Fe (3a), (η5-2-SiMe3–C9H6)2Fe (3b), [η5-1,2-(SiMe3)2C9H5]2Fe (4a) and [η5-1,3-(SiMe3)2C9H5]2Fe (4b), by the reaction of the appropriate lithium indenide salts [prepared from 1-SiMe3–C9H7 (2a), 2-SiMe3–C9H7 (2b), 1,2-(SiMe3)2C9H6 (2c) or 1,3-(SiMe3)2C9H6 (2d)] with ferrous chloride (1) in a 2:1 molar ratio is discussed. The solid-state structure of 4b was determined by single-crystal X-ray diffractometry. Complex 4b exists in a gauche conformation, showing that the indenyl ligands are sterically imposed by the bulk of the Me3Si substituents. The average Fe–C distance is 2.091(3) Å. Cyclovoltammetric studies indicate that 3 and 4 are redox-active with one-electron oxidations [E1/2=−270 to −360 mV versus Fc/Fc+, Fc=(η5-C5H5)2Fe].