Sterically Congested Ligands: Synthesis and Solution Conformation of Bisphosphite Ligand Precursors

Abstract

The synthesis and characterization of precursors to sterically hindered bisphosphite ligands containing the dibenzo[d,f][1,3,2]dioxaphosphepin and dibenzo[d,g][1,3,2]dioxaphosphocin ring system is described. The δG ^# for ring inversion of the dibenzo[d,f][1,3,2]dioxaphosphepin ring was determined by VT ³¹P(¹H) NMR spectroscopy. The ¹H NMR spectra of the dibenzo[d,g][1,3,2]dioxaphosphocin ligands were consistent with the eight-membered ring adopting a boat-chair conformation in solution.

Key Words:

• Ligand, dibenzo[d,f][1,3,2]dioxaphosphepin ring
• dibenzo[d,g][1,3,2]dioxaphosphocin ring
• conformational analysis
• δG ^# for ring inversion