Diphosphine−Phosphenium Coordination Complexes Representing Monocations with Pendant Donors and Ligand Tethered Dications

Homoatomic P−P coordinate bonding is exploited to prepare the first examples of triphosphorus
monocations and tetraphosphorus dications using dimethylphosphenium or diphenylphosphenium Lewis
acceptors with diphosphinomethane, diphosphinoethane, diphosphinohexane, or diphosphinobenzene
ligands. Solid-state structures and spectroscopic characterization data for complexes involving bis(diphenylphosphino)methane ligands show coordination of only one donor site of the diphosphine ligand in the
monocations, and chelate complexation is not observed. Tetraphosphorus dications are observed with
longer diphosphines, in which the ligand tethers two phosphenium acceptors. The structural preferences
between monocations with pendant phosphines and tethered dications are dependent on intramolecular
steric interactions and the flexibility of the tether.