MAdPHOS, a P‑Stereogenic Aminodiphosphane Ligand withAdamantyl Groups: Synthesis, NH/PH Tautomerism, and Rhodiumand Nickel Complexes.

Abstract

A novel chiral ligand, named MAdPHOS, bearing aP-stereogenic phosphane and a diadamantyl phosphane linked by aNH bridge has been synthesized. This bulky, C1-symmetric, PNPligand has been prepared from enantiopure tert-butylmethylaminophosphane and was obtained as a crystalline solid. TheNH/PH tautomerism, air-stability, and σ-donor capacity ofMAdPHOS have been assessed herein. The free ligand has beenprepared, showing much higher stability, in the solid form, than itstert-butyl analogue MaxPHOS. Both rhodium and nickel CODcomplexes have been prepared. The Rh-MAdPHOS complex hasshown outstanding enantioselectivities in the asymmetric hydrogenationof enamides.