An enantiomerically pure P-stereogenic bisphosphine: (S,S)-ethylenebis[(2-methylphenyl)phenylphosphine] (o-tolyl-DiPAMP).

In connection with a research program involving the synthesis, structure determination, reactivity and ability to coordinate to metal centres of chiral bis­phosphine ligands, we have synthesized and structurally characterized, by means of single-crystal X-ray diffraction analysis, the title compound {systematic name: (S,S)-(ethane-1,2-di­yl)bis­[(2-methyl­phen­yl)phenyl­phosphane], abbreviated as o-tolyl-DiPAMP}, C28H28P2. So far, neither the free bisphosphine (DiPAMP) nor analogues that incorporate the ethyl­enebisphosphine frame have had their crystal structures reported. The investigated compound forms crystals which are isostructural with the bis­phosphine dioxide analogue [King et al. (2007). Acta Cryst. E63, o3278], despite the involvement of the dioxide in C—H⋯O(=P) hydrogen bonds and the lack of similar hydrogen bonds in the investigated crystal structure. In both mol­ecules, the P—C—C—P chain is in a trans conformation, extended further at both ends by one of the two P—Cipso bonds. The planes of the phenyl and o-tolyl rings attached to the same P atom are nearly perpendicular to one another. Both crystal structures are mainly stabilized by dispersive inter­actions.