(
R)- and(
S)-1,3-bis(diphenylphosphino)-2-((diphenylphosphino)methyl)-1-phenylpropane((
R)- and (
S)-heliphos) were synthesized via anacid-catalyzed, diastereoselective Michaeladdition of diphenylphosphine tobis(1
R,2
S,5
R)-(-)-menthyl)benzylidenemalonate. Thecrystal structure of[Rh((
R)-heliphos)(NBD)](ClO
4)was determined by X-ray diffraction. Aspredicted by studies of molecular models, the framework of coordinated(
R)-heliphos adopteda left-handed (
) helical conformation in the solid state, and NMRexperiments indicatedthat it strongly favored this conformation in solution as well.The sense of helicity wascontrolled by the absolute configuration of the stereogenic carbon atomin the ligand.