CATALYTIC SYNTHESES OF POLYCYCLIC COMPOUNDS BASED ON NORBORNADIENE-2,5 IN THE PRESENCE OF NICKEL-COMPLEXES - I - A CHOICE OF THE MODEL FOR CYCLIC [2-PI-PI]-DIMERIZATION OF NORBORNADIENE-2,5(2)

The formation of Ni(0)-norbornadiene-2,5 complexes, which are efficien t catalysts for [2 pi + 2 pi]-cyclodimerization of norbornadiene-2,5 ( NBD), was studied. The analysis of processes occurring during the indu ction period of the catalytic reaction of NBD and the results of eleme ntal analyses of isolated intermediates suggest that the formation of true catalysts of NBD dimerization occurs in a similar manner if diffe rent initial nickel compounds are used, The true catalysts may be mono nuclear homoligand nickel complexes with two or three NBD molecules as ligands. These complexes are in equilibrium with each other. The cata lytic system formed from bis(eta(3)-allyl)nickel is a convenient model for the ongoing research into the catalytic processes and process opt imization.