Diferrocenylmercury‐Bridged Diphosphine: A Chiral,Ambiphilic, and Redox‐Active Bidentate Ligand

A diphosphine chelate ligand with a wide and flexible bite angle, a unique stereochemical environment, and redox‐active and ambiphilic character is reported. Initially generated as its HgCl₂ complex by reaction of 1,2‐fc(PPh₂)(SnMe₃) (fc=ferrocenediyl) with HgCl₂ in acetone, treatment with [n‐Bu₄N]CN readily liberates the free chiral bidentate ligand. An intermolecular ClHg−Cl→Hgfc₂ (2.9929(13) Å) interaction that is unprecedented in ambiphilic ligand chemistry is seen in the solid structure of Hg(fcPPh₂)₂⋅HgCl₂ where the bridging mercury atom acts as a σ‐acceptor. Furthermore, a bis‐[Rh(COD)Cl] complex is introduced, which displays relatively short Rh⋅⋅⋅Hg contacts of 3.4765(5) and 3.4013(1) Å. Wiberg indices of 0.12 are determined for these Rh⋅⋅⋅Hg interactions and an AIM analysis reveals bond paths with an electron density ρ(r) of 1.2×10⁻² and 1.4×10⁻² e/a₀³ at the bond critical points.     

Diferrocenophosphaborin: A Planar‐Chiral,Redox‐Active and Anion‐Responsive Ambiphilic Ligand

A new class of Janus‐like ambiphilic ligands is introduced. The rigid diferrocene backbone in heterocycles 4‐SnP and 4‐BP creates an unprecedented chiral environment as demonstrated by multinuclear NMR and single‐crystal X‐ray studies. In addition, the ligands are redox‐responsive and the Lewis acidic borane moiety in 4‐BP can be exploited to further tune the properties: a clear decrease in the CO stretching frequency of a Vaska‐type Rh^I complex 5‐BP is observed upon addition of fluoride ions. Thus, the Lewis acid and Lewis base sites influence each other and their strength can be modulated by redox chemistry and anion binding.     

Diferrocenylmercury‐Bridged Diphosphine: A Chiral,Ambiphilic, and Redox‐Active Bidentate Ligand

A diphosphine chelate ligand with a wide and flexible bite angle, a unique stereochemical environment, and redox‐active and ambiphilic character is reported. Initially generated as its HgCl₂ complex by reaction of 1,2‐fc(PPh₂)(SnMe₃) (fc=ferrocenediyl) with HgCl₂ in acetone, treatment with [n‐Bu₄N]CN readily liberates the free chiral bidentate ligand. An intermolecular ClHg?Cl→Hgfc₂ (2.9929(13) Å) interaction that is unprecedented in ambiphilic ligand chemistry is seen in the solid structure of Hg(fcPPh₂)₂?HgCl₂ where the bridging mercury atom acts as a σ‐acceptor. Furthermore, a bis‐[Rh(COD)Cl] complex is introduced, which displays relatively short Rh???Hg contacts of 3.4765(5) and 3.4013(1) Å. Wiberg indices of 0.12 are determined for these Rh???Hg interactions and an AIM analysis reveals bond paths with an electron density ρ(r) of 1.2×10^?2 and 1.4×10^?2 e/a₀³ at the bond critical points.     

C−H and C−N Activation at Redox‐Active Pyridine Complexes of Iron

Pyridine activation by inexpensive iron catalysts has great utility, but the steps through which iron species can break the strong (105–111 kcal mol⁻¹) C−H bonds of pyridine substrates are unknown. In this work, we report the rapid room‐temperature cleavage of C−H bonds in pyridine, 4‐tert‐butylpyridine, and 2‐phenylpyridine by an iron(I) species, to give well‐characterized iron(II) products. In addition, 4‐dimethylaminopyridine (DMAP) undergoes room‐temperature C−N bond cleavage, which forms a dimethylamidoiron(II) complex and a pyridyl‐bridged tetrairon(II) square. These facile bond‐cleaving reactions are proposed to occur through intermediates having a two‐electron reduced pyridine that bridges two iron centers. Thus, the redox non‐innocence of the pyridine can play a key role in enabling high regioselectivity for difficult reactions.     

Individual (f,tA)‐ and (f,tC)‐Fullerene‐Based Nickel(II) Glycinates: Protected Chiral Amino Acids Directly Linked to a Chiral π‐Electron System

Stereoselective electrosynthesis of the first individual (^f,tA)‐ and (^f,tC)‐1,4‐fullerene derivatives with a non‐inherently chiral functionalization pattern is described, as well as the first example of an optically pure protected primary amino acid directly linked to the fullerene through only the chiral α‐amino‐acid carbon atom. An application of an auxiliary chiral nickel‐Schiff base moiety as derivatizing agent allowed separation of (^f,tA)‐ and (^f,tC)‐1,4‐fullerene derivatives using an achiral stationary phase, a separation which has never been done before.