PPh(3) Propeller Diastereomers: Bonding Motif Ph(PPh(3)) Face-On π-Ar in Half-Sandwich Compounds [(π-Ar)LL'MPPh(3)].

Chiral-at-metal compounds (R (Ru),S (C))/(S (Ru),S (C))-[CyRu(1O-2N)PPh(3)]PF(6) and (R (Ru),S (C))/(S (Ru),S (C))-[CyRu(2O-1N)PPh(3)]PF(6) were prepared using anions 1O-2N(-) and 2O-1N(-) of the Schiff bases, derived from the hydroxynaphthaldehydes and (S)-1-phenylethylamine. The pure (R (Ru),S (C))-diastereomers were obtained by crystallization. In the unit cell of (R (Ru),S (C))-[CyRu(1O-2N)PPh(3)]PF(6), there are three independent molecules, which differ in the propeller sense of the PPh(3) ligand. Molecules [1] and [2] have (M (PPh(3)) )-configuration and molecule [3] has (P (PPh(3)) )-PPh(3) configuration. PPh(3) diastereoisomerism is discussed including other pairs of compounds, differing only in the PPh(3) configuration. A conformational analysis reveals an internal stabilization inside the PPh(3) ligand by a system of attractive CH/π interactions and a new bonding motif Ph(PPh(3)) face-on π-Ar, both characteristic features of [(π-Ar)LL'MPPh(3)] compounds. The propeller diastereomers interconvert via a low-energy pathway and a high-energy pathway, corroborated by density functional theory calculations.