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.

A new class of planar chiral heteroatom-bridged biferrocene species was prepared using (pR,pR,S S ,S S )-2,2″-bis(p-tolylsulfinyl)-1,1″-biferrocene (pR,pR,S S ,S S )-2 as a readily accessible precursor. Initially, one of the sulfinate groups in compound 2 is replaced with a trimethylstannyl or dimesitylboryl group. Replacement of the second sulfinate group with t-BuLi then results in cyclization to give the Me 2 Sn-bridged species (pS,pS)-4Sn and the Mes 2 B-bridged borate anion [(pS,pS)-4B] − . The products are redox active, as cyclic and square wave voltammetry data of (pS,pS)-4Sn and [Li(12-c-4) 2 ][(pS,pS)-4B] reveal two separate reversible oxidation events. The mixed-valent species [(pS,pS)-4Sn] + and (pS,pS)-4B can also be obtained by chemical oxidation with AgPF 6 or by simple exposure to air, respectively. A comparison of X-ray crystal structures reveals that the oxidized (mixed-valent) species contain distinct Fe(II) and Fe(III) sites, but UV−visible−NIR spectra display IVCT bands at ca. 4000 and 5000 cm −1 , indicative of electronic coupling in solution. All compounds are obtained in enantiomerically pure form, suggesting potential use as switchable chiral anions and cations.

An ew 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.I na ddition, the ligands are redox-responsive and the Lewis acidic borane moiety in 4-BP can be exploited to further tune the properties:aclear decrease in the CO stretching frequency of aV aska-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.