Substitutional Lability of Diphosphine Ligands in Tetrahedral Iron(II) Chloro Complexes

Abstract

A series of iron(II) dihalogenide complexes with two different bisphosphinoethane ligands is reported. In the case of 1,2bis(diphenylphosphanyl)ethane (dppe), depending on the stoichiometry, the tetrahedral [(μ-dppe)FeCl 2 ] n and octahedral trans-[(dppe) 2 FeCl 2 ] complexes are formed. The polymeric complex [(μ-dppe)FeCl 2 ] n , with iron in a tetrahedral environment, preferentially reacts with chelating amines to give the octahedral diphosphine complex, trans-[(dppe) 2 -FeCl 2 ], and different octahedral amine complexes. With the [a]141 sterically more demanding 1,2-bis(diisopropylphosphanyl)ethane (dippe), the monomeric and tetrahedral halogen complexes [(dippe)FeX 2 ] are exclusively obtained (X = Cl, Br). These complexes react with chelating amines in a similar manner, to give free ligand and the corresponding octahedral amine complex. The present results suggest that the diphosphines in the investigated iron(II) complexes are bound too weakly to form productive catalyst precursors.

From Ruthenium to Iron and Manganese—A Mechanistic View on Challenges and Design Principles of Base‐Metal Hydrogenation Catalysts

“…Fe II complexes in a very weak ligand field form tetrahedral complexes, which are catalytically inactive. As a consequence, it was not possible to synthesize an iron analogue of the ruthenium diamine diphosphine complexes reported by Noyori . Notably, Noyori‐type catalysts are well known for their use in asymmetric hydrogenation reactions, giving access to compounds such as α‐amino‐ or α‐alkoxy‐alcohols in high enantiomeric excess .…”

Umpolung at Boron: Ancillary‐Ligand‐Induced Formation of Boron‐Based Donor Ligands from Phosphine‐Boranes

“…Using the easily accessible iron phosphine‐borane complex I , which contains both a chelating phosphine‐borane ligand and a potentially cooperative site (proton relay), we herein confirm the dehydrogenative pathway A → D by isolation of several intermediates and report the formation of an unusual pincer‐type complex with a central donor group that is based on tricoordinate boron. Moreover, we demonstrate that the dominant pathway is highly dependent on the utilized ancillary ligand, ranging from simple hydride protonation and subsequent H 2 liberation to dehydrogenative Fe−B bond formation.…”

“…BH{PR 3 } 2 ). [25] Using the easily accessible iron phosphine-borane complex I, which contains both ac helating phosphine-borane ligand and ap otentially cooperative site (proton relay), [26] we herein con-Scheme1.To p:…”

Synthesis and reactivity of iron(II) hydride complexes containing diphenylphosphine ligands

“…In a recent study, we were able to demonstrate that iron(II) dihalide complexes with certain chelating diphosphines and a chelating amine ligand, analogous to the ruthenium complexes reported by Noyori and co-workers, are not generally accessible [15]. As secondary phosphines have a sufficiently small Tolman cone angle, the coordination of four of such ligands to the central iron(II) atom should be possible and potentially allow for the preparation of stable dihydride complexes.…”