Nuclear magnetic resonance shift reagents: Evidence for different mechanisms of contact contributions to 13C shifts induced by nickel and cobalt acetylacetonates with saturated amines and alcohols

The pattern of 13C and 1H nuclear magnetic resonance (NMR) shift changes produced by complexation of cobalt and nickel acetylacetonates with amines and alcohols indicates that there is more than one mode of operation of the contact interaction. A large effect with alternating signs is important at the α and ß carbons, but this effect seems to be overlaid by another influence that appears to fall off monotonically as one proceeds away from the site of complexation