STRUCTURAL STUDIES ON PRODUCTS OF REDUCTION OF A NITRO-NI1C3N2-METALLOCENE

The reduction of oxa-5-hydra-tetradeca-2,7,10,12-tetrene)nickel(II) (N ioyl-NO2), with Zn(s) and NaOH or HCl solution or utilizing Pd-H-2 und er most conditions produces an intensely purple complex ion epsilon((m ax)) at 552 nm which is not the expected amine. This product was found to be a conjugated dimer ion with two Nioyls multiply bonded to a sin gle nitrogen atom. It was shown that the initial reduction produces th e amine or amine hydrochloride which oxidizes rapidly in the presence of traces of O-2 under low acidity conditions to the dimer. Under high acidity conditions the amine salt is isolated. The X-ray crystal stru ctures of three complexes are described: [(Nioyl)(2)NH](ClO4)(2) . 2.5 CCl(4), [(Nioyl-NH3)(2)H]ZnCl(4)Cl3H(2)O, [Nioyl-NH3]H-0.5(ClO4)(1.5) . 2CH(3)CN . 2H(2)O and structural differences are discussed. The 2e(- ) reduction of [(Nioyl)(2)N](+) with dithionite ion reversibly gives t he yellow [(Nioyl)(2)NH](+) which is extremely sensitive to air oxidat ion. A postulated reaction sequence is presented and discussed to expl ain the formation of the highly stable conjugated dimeric purple produ ct.