Rigid trans-spanning triptycene-based ligands: How flexible they can be?

trans-[1,8-Bis(diisopropylphosphino)triptycene]nickel (II) dichloride, trans-[1,8-bis(diisopropylphosphino)triptycene]carbonylrhodium (I) chloride and cis-[1,8-bis(diisopropyl-phosphino)triptycene] platinum (II) dichloride have been prepared and fully characterized in order to evaluate the coordination diversity of triptycene-based bidentate ligands. Their structural features and coordination preferences were studied and compared to the previously reported palladium complexes. The comparative structural analysis revealed that 1,8-bis(diisopropylphosphino)triptycene is able to access a variety of bite angles and to stabilize metal centers in different geometries. In addition, intramolecular weak C–H⋯Cl–Pt hydrogen bonding interactions which stabilize [1,8-bis(diisopropyl-phosphino)triptycene] platinum (II) dichloride in a constrained cis form are discussed.