Triphenylphosphine─Closed-Shell Metal Cation Interactions.

The interactions between group 1 and 11 monocations and group 2 dications with triphenylphosphine were studied by using a combination of correlated molecular orbital theory and density functional theory. Two binding modes were found: the front side (phosphorus lone pair) and back side (phenyl rings). Group 1 and 2 cations prefer binding to the π system rather than to the lone pair of the phosphorus atom, and their ligand binding energies (LBEs) correlate with the atomic ionic radii as well as the hardness of the atomic ion. Group 11 monocations prefer binding to the lone pair of the phosphorus atom, and their LBEs are correlated with the hardness of the cation but exhibit a different trend than for the groups 1 and 2 cations. The LBEs of the cations with C 2 H 4 , C 6 H 6 , and C 6 H 5 PH 2 are also reported to aid in the analysis of the cation-π interactions and the influence of the PH 2 substituent on the energy of this interaction. The LBEs for binding to C 2 H 4 and C 6 H 6 are the most complete and reliable set of values for these species.