(Indenyl)Iron Complex [(η⁵‐indenyl)Fe(η‐C₆H₆)]⁺: Synthesis, Arene Exchange Reactions and Bonding

Abstract

The indenyl‐benzene complex [(η5‐indenyl)Fe(η‐C6H6)]+ (2) was synthesized by photochemical reaction of the cyclohexadienyl derivative [(η5‐C6H7)Fe(η‐C6H6)]+ and indenyl anion with the subsequent treatment of complex (η5‐C6H7)Fe(η5‐indenyl) formed by acetic acid. Visible light irradiation of cations [(η5‐indenyl)Fe(η6‐indene)]+ (1) or 2 in the presence of substituted benzenes in CH2Cl2 results in arene exchange giving [(η5‐indenyl)Fe(η6‐arene)]+ (arene=o‐xylene (3 a), mesitylene (3 b), hexamethylbenzene (3 c) and [2.2]paracyclophane (3 d)). The rate of this reaction is lower than for the related cyclopentadienyl complex [CpFe(η‐C6H6)]+. μ‐Pentaphospholyl triple‐decker complex [(η5‐indenyl)Fe(μ‐η:η‐cyclo‐P5)FeCp*]+ (4) was synthesized by photochemical reaction of 1 with Cp*Fe(η‐cyclo‐P5). The structures of 2PF6, 3 cPF6 and 4PF6 were determined by X‐ray diffraction. According to energy decomposition analysis, the metal‐benzene bonding in 2 is weaker than in [CpFe(η‐C6H6)]+ but stronger than in [Cp*Fe(η‐C6H6)]+. The mechanism of thermal benzene replacement in 2 and [CpFe(η‐C6H6)]+ as well as structure of excited state were analyzed by DFT calculations.

Indenyl Rhodium Complexes with Arene Ligands: Synthesis and Application for Reductive Amination

“…The carborane and triple-decker derivatives showed lower reactivity in the arene exchange reaction in comparison to the cyclopentadienyl and indenyl complexes (entries 10–12 vs entries 7 and 9). In general, the salts with a tetrafluoroborate anion are considerably more reactive than those with a hexafluoroantimonate anion (entry 3 vs entry 1 as well as entry 7 vs entry 5), suggesting the crucial participation of counterions in replacement of the arene ligand . The latter is in accordance with the difficulty in isolating cations 2a – e as salts with the BF 4 – anion in pure form (vide supra).…”