developed by noyori, binap (2,2'-diphenylphosphino-1,1'-binaphthyl) is a family of chiral diphosphine ligands featuring two triarylphosphine moieties installed on a binaphthalene backbone. binap chelates onto a metal (usually a late transition metal) to form a "c"-symmetric complex. as shown below in the structure of an "(r)"-binap ruthenium complex, among the four remaining coordination sites on an octahedral metal center, the two equatorial sites (purple) are strongly influenced by the equatorial phenyl groups, while the two axial sites (green) are influenced by the axial phenyl groups.