STERICALLY CONGESTED LIGANDS - SYNTHESIS AND SOLUTION CONFORMATION OF BISPHOSPHITE LIGAND PRECURSORS

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 Delta G double dagger for ring inversion of the dibenzo[d,f][1,3,2]dioxaphosphepin ring was determined by VT P-31{H-1} NMR spectroscopy The H-1 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.