Crystal structures of bis-[2-(di-phenyl-phosphino-thio-yl)phen-yl] ether and bis-{2-[diphen-yl(selanyl-idene)phosphan-yl]phen-yl} ether.

The title compounds, C36H28OP2S2, (1), and C36H28OP2Se2, (2), exhibit remarkably similar structures although they are not isomorphous. The whole mol-ecule of compound (2) is generated by twofold symmetry, with the ether O atom located on the twofold axis. Both compounds have intra-molecular π-π inter-actions between terminal phenyl rings with centroid-centroid distances of 3.6214 (16) and 3.8027 (14) Å in (1) and (2), respectively. In the crystal of (1), short C-H⋯S hydrogen bonds link the mol-ecules, forming chains along [001], while in (2) there are no analogous C-H⋯Se inter-actions present.