Spin delocalization from paramagnetic metal complexes [Cr(acac) 3 and Fe(acac) 3 ] to saturated hydrocarbons in CHCl 3 and CCl 4 solutions

Paramagnetic 13 C NMR shifts induced by tris(acetylacetonato)chromium(III) [Cr(acac) 3 ] and tris(acetylacetonato)iron(III) [Fe(acac) 3 ] in various saturated hydrocarbons were determined for the first time using a special technique. The observed shifts, Δδ spec , are the result of partial delocalization of unpaired electrons from the paramagnetic complexes on the alkanes. The value of Δδ spec depends strongly on the position of a carbon atom in the hydrocarbon molecule, and tends to decrease on passing from primary to quaternary carbon atoms. The observed spin transfer seems to reflect the ‘contact charge transfer.’ The Δδ spec shifts in the unsaturated hex‐1‐ene only slightly exceed those in alkanes.