Monocyclopentadienyl and Other Half-Sandwich Complexes of Iron

Ammonium and Phosphonium Salts Containing Monoanionic Iron(II) Half-Sandwich Complexes [Fe(η5-Cp*)X2]− (X = Cl − I)

“…In view of the unsatisfactorily low yield, elemental analysis was not performed for this compound. 1 [Fe(η 5 -Cp*)Cl(CO) 2 ]: A solution of NnPr 4 [Fe(η 5 -Cp*)Cl 2 ] (40 mg, 0.09 mmol) in THF (2 mL) was subjected to an atmospheric pressure of CO, which led to an immediate colour change from green to red. The solution was stirred for 10 min.…”

“…Half-sandwich iron(II) complexes of the type [Fe(η 5 -Cp')X] (Cp' = C 5 H 5 or substituted cyclopentadienyl; X = Cl, Br, I) are useful as highly reactive cyclopentadienyliron(II) transfer reagents, which, due to their thermal lability, are usually generated in situ at low temperatures for immediate use [1]. Seminal work was published in 1985 by Kölle, who described the generation of [Fe(η 5 -Cp*)Br] (Cp* = C 5 Me 5 ) from LiCp* and [FeBr 2 (DME)] in THF at −80 • C [2].…”

“…This dinuclear complex might be viewed as a contact ion pair [Na(DME) 2 ][Fe(η 5 -C 5 H 2 -1,2,4-tBu 3 )Br 2 ], thus exhibiting, cum grano salis, the [Fe(η 5 -C 5 H 2 -1,2,4-tBu 3 )Br 2 ] − anion. In view of the mature state of half-sandwich iron(II) chemistry [1], the paucity of compounds containing simple anions of the type [Fe(η 5 -Cp')X 2 ] − is quite surprising. Together with the enormous popularity of the Cp* ligand [25], this prompted us to address the synthesis of compounds containing [Fe(η 5 -Cp*)X 2 ] − (X = Cl, Br, I).…”

Low-Coordinate Iron(II) Amido Half-Sandwich Complexes with Large Internal Magnetic Hyperfine Fields

“…In particular, the cyclopentadienyl (Cp) ligands are appealing to obtain heteroleptic metal complexes with N-heterocyclic carbene (NHC), , imidazolin-2-iminato, , amido, − phenoxo, or aryl ligands (Figure ). − In the past, low-coordinate, quasi-linear iron half-sandwich complexes bearing functionalized Cp and amido ligands were synthesized with various substitution patterns at the nitrogen atom . Compounds C and D (Figure c), featuring the pentamethylcyclopentadienyl (η 5 -C 5 Me 5 , Cp*) and pentaisopropylcyclopentadienyl (η 5 -C 5 i Pr 5 or 5 i Pr Cp) ligands, approach a nearly linear structure with Cp–Fe–N angles of 172.4° and 177.9°, respectively.…”

“…19−22 In the past, low-coordinate, quasi-linear iron half-sandwich complexes bearing functionalized Cp and amido ligands were synthesized with various substitution patterns at the nitrogen atom. 23 Compounds C and D (Figure 1c), featuring the pentamethylcyclopentadienyl (η 5 -C 5 Me 5 , Cp*) and pentaisopropylcyclopentadienyl (η 5 -C 5 i Pr 5 or 5iPr Cp) ligands, approach a nearly linear structure with Cp−Fe−N angles of 172.4°1 5 and 177.9°, 24 respectively. Employing the sterically demanding 1,2,4-tri-tert-butylcyclopentadienyl (η 5 -1,2,4-t Bu 3 C 5 H 2 , Cp′), the paramagnetic halfsandwich compounds Fe-tms, Fe-t Bu, and E (Figure 1c) were isolated.…”