PPh3 Propeller Diastereomers: Bonding MotifPhPPh3 Face-On π-Ar in Half-SandwichCompounds (π-Ar)LL′MPPh3

摘要

Chiral-at-metal compounds (RRu,SC)/(SRu,SC)-[CyRu(1O-2N)PPh3]PF6 and (RRu,SC)/(SRu,SC)-[CyRu(2O-1N)PPh3]PF6 were prepared using anions 1O-2N^– and 2O-1N^– of the Schiff bases, derived from the hydroxynaphthaldehydes and (S)-1-phenylethylamine. The pure (RRu,SC)-diastereomers were obtained by crystallization. In the unit cell of (RRu,SC)-[CyRu(1O-2N)PPh₃]PF₆, there are three independent molecules, which differ in the propeller sense of the PPh₃ ligand. Molecules [1] and [2] have (M_PPh3)-configuration and molecule [3] has (P_PPh3)-PPh₃ configuration. PPh₃ diastereoisomerism is discussed including other pairs of compounds, differing only in the PPh₃ configuration. A conformational analysis reveals an internal stabilization inside the PPh₃ ligand by a system of attractive CH/π interactions and a new bonding motif Ph_PPh3 face-on π-Ar, both characteristic features of [(π-Ar)LL′MPPh₃] compounds. The propeller diastereomers interconvert via a low-energy pathway and a high-energy pathway, corroborated by density functional theory calculations.