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

• Published in: Angewandte Chemie International Edition 2018-05, Vol.57 (22), p.6552-6557
• Main Authors: Tagne Kuate, Alain C., Lalancette, Roger A., Bannenberg, Thomas, Jäkle, Frieder
• Format: Article
• Language: English
• Subjects: Acetone; ambiphilic ligands; Chelates; Electron density; ferrocene; Ligands; Mercuric chloride; Mercury; Mercury (metal); Mercury compounds; phosphines; planar chirality
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201803086

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. Flexible phosphine: Reaction between 1,2‐Fc(PPh2)(SnMe3) and HgCl2 is accompanied by spontaneous disproportionation to give a diphosphine chelate ligand with a wide and flexible bite angle and unique stereochemical environment. Its HgCl2 complex shows unprecedented Hg−Cl→HgR2 interactions that give rise to a polymeric structure, whereas ambiphilic behavior with short Rh⋅⋅⋅Hg contacts is found for a RhI complex.