An η<sup>2</sup>-Aryl−Metal Interaction Turns a Chiral Monodentate Phosphoramidite into a Chelating Ligand in (<i>S<sub>a</sub></i>,<i>S<sub>Ru</sub></i>,<i>R<sub>C</sub></i>,<i>R<sub>C</sub></i>)-[RuCl(η<sup>6</sup>-<i>p</i>-cymene) (<i>O</i>,<i>O</i>‘-(1,1‘-dinaphthyl-2,2‘-diyl)-<i>N</i>-(1-(1,2-η-1-naphthyl)ethyl)- <i>N</i>-(1-(1-naphthyl)ethyl)phosphoramidite-κ<i>P</i>)]PF<sub>6</sub>
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Chloride abstraction from the half-sandwich complex [RuCl2(η6-p-cymene)(1-κP)] (2; 1 = (Sa,RC,RC)-O,O‘-(1,1‘-dinaphthyl-2,2‘-diyl)-N,N-bis(1-(1-naphthyl)ethyl)phosphoramidite) with TlPF6 or (Et3O)PF6 gives the cationic, 18-electron complex (Sa,SRu,RC,RC)-[RuCl(η6-p-cymene)(O,O‘-(1,1‘-dinaphthyl-2,2‘-diyl)-N-(1-(1,2-η-1-naphthyl)ethyl)-N-(1-(1-naphthyl)ethyl)phosphoramidite-κP)]PF6, (Sa,SRu,RC,RC)-3, which features the η2-coordination of a naphthyl substituent of the phosphoramidite ligand, as indicated by 1H, 13C, and 31P NMR spectroscopy and by X-ray studies. Complex (Sa,SRu,RC,RC)-3 catalyzes the asymmetric cyclopropanation of styrene and α-methylstyrene with ethyl diazoacetate, giving good enantioselectivities for the latter olefin (up to 86% and 87% ee for the cis- and the trans-cyclopropane, respectively) when formed in situ in the presence of an excess of 1 to suppress ligand dissociation.
