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-Bu4 N]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.