2 a ) and ( 2 b ) can be explained by the Karplus equation[41, paying attention to the group electronegativity [51 of the substituents "61, and the ally1 coupling can be interpreted satisfactorily in terms of a relationship given by Garbisch"].It can be assumed with a high degree of certainty that N is fixed exclusively cis to the Fe2(C0)6 group, thus suggesting that the attacking nucleophile is transferred onto the ring by the agency of the metal.