Toward the synthesis and characterization of BIPHEP and OMe-BIPHEP ligands bearing bis(ortho-substituted phenyl)phosphino groups

Melissa A. Bouchard, William R. Lopez, Ayse B. Cemek, Kelly A. Swain, Lila J. Marlowe, Olivier Y. Servius, Alex Alba, Ashleigh D. Roberts, Rebecca E. Black

New College of Florida

The tunability of diphosphine ligands has allowed for significant advances in transition metal catalysis. Our research group is interested in developing more active alcohol acceptorless dehydrogenation (AAD) catalysts by preparing new ligands, specifically derivatives of 2,2’-(bis(diphenyl)phosphino)biphenyl (BIPHEP) and 2,2'-(bis(diphenyl)phosphino)-6,6'-dimethoxy-1,1’-biphenyl (OMe-BIPHEP). Many BIPHEP and OMe-BIPHEP ligands have been reported bearing meta- and para- substituents on the diarylphosphino (-PAr2) groups. However, there are no literature article reports of BIPHEP-type ligands with ortho-subtituents on the -PAr2 groups of these BIPHEP-type ligands. We hypothesize that ortho-subtituents will affect the BIPHEP dihedral angle, which has been shown to influence the performance of transition metal-BIPHEP complexes in asymmetric catalysis. This presentation will discuss our synthetic efforts toward a series of ortho-substituted BIPHEPs and OMe-BIPHEPs via appropriate biphenyl bisphosphonate intermediates as well as NMR and IR characterization of intermediates and products. Ru(II) complexes bearing these new ligands will be synthesized, characterized, and tested in AAD catalysis.