X-ray Diffraction, PGSE Diffusion, and Related NMR Studies on a Series of Cp*-Based Ru(IV)(Cp*)(η3-CH2−CH−CHPh) Allyl Complexes

Abstract

The new ruthenium (IV) allyl complexes [Ru(Cp*)Cl(DMF)(η3-CH2−CH−CHPh)](PF6) (2b) and [Ru(Cp*)Cl(t-BuCN)(η3-CH2−CH−CHPh)](PF6) (2c) have been prepared and their structures determined. These results are compared with the analogous X-ray data for [Ru(Cp*)Cl(CH3CN)(η3-CH2−CH−CHPh)](PF6), [Ru(Cp*){OC(O-t-Bu)O}(η3-CH2−CH−CHPh)](PF6), [Ru(Cp*)(CH3CN)2(η3-CH2−CH−CHPh)](PF6)2, and [Ru(Cp*)(DMF)2(η3-CH2−CH−CHPh)](PF6)2. In all of the structures, the Ru−((η3-CH2−CH−CHPh) moiety is markedly distorted such that Ru−CPh(allyl) separation is much longer than the remaining two Ru−C(allyl) distances. The DMF and acetonitrile ligands are shown to exchange on the NMR time scale via both variable-temperature and 2-D exchange spectroscopy. Pulsed gradient spin−echo (PGSE) diffusion and 1H,19F HOESY NMR methods show that there is relatively little ion pairing in these salts in DMF and acetonitrile solutions. The PF6 anions take up specific positions with respect to the Ru(IV) cations.