Paramagnetic complexes of nickel(I) stabilized by norbornadiene

Nickel(I) compounds whose concentration was 10^–4–10^–6 of the total concentration of nickel added to the system were identified by EPR in the reaction of 2,5-norbornadiene with nickel homoligand allyl complexes Niall₂ (all is C₃H₅, 1-CH₃C₃H₄, or 2-CH₃C₃H₄). The Ni(I) complexes were stable at room temperature under oxygen-free conditions. It was shown that the paramagnetic complexes were in equilibrium with diamagnetic forms. The temperature dependence of the concentration of the paramagnetic species was determined. The structure of the paramagnetic nickel(I) complexes and the possible routes of their formation are discussed on the basis of the obtained data.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 4, pp. 490–493, July–August, 1990.