A Chiral Phosphoramidite beyond Monodentate Coordination: Secondary π-Interactions Turn a Dangling Aryl into a Two-, Four-, or Six-Electron Donor in d6 and d8 Complexes

Abstract

A study of the secondary interactions involving a pendant phenethyl group (NCH(CH3)Ph) of (Sa,RC,RC)-O,O′-[1,1′-binaphthyl-2,2′-diyl]-N,N′-bis[1-phenylethyl]phosphoramidite (1) in d8 and d6 metal complexes is reported. A 1,2-η-phenyl interaction is found in [Pd(η3-allyl)(1,2-η-Ph-1-κP)]+ (3), as indicated by NMR spectroscopy and by an X-ray study. The Rh(I) complexes [RhCl(NBD)(1-κP)] (4a) and [RhCl(COD)(1-κP)] (4b) were prepared, and their X-ray structures were determined. Chloride abstraction from 4a and 4b gave the corresponding cations [Rh(NBD)(1,2-η-Ph-1-κP)]+ (5a) and [Rh(COD)(1,2-η-Ph-1-κP)]+ (5b), which were fully characterized. Besides NMR spectroscopic data, the 1,2-η-phenyl interaction is supported by an X-ray study of 5a. Upon standing in MeOH solution, 5b undergoes loss of the COD and forms [Rh(1-κP)(η6-Ph-1-κP)]+ (6), whose η6-arene coordination was studied by NMR spectroscopy and by X-ray diffraction. For the sake of comparison with the d8 complex 6, the crystal structure of the previously ...