REACTION OF (1,4-DIAZABUTADIENE)BIS(ALKENE)NICKEL(0) COMPLEXES WITH ETHYNE

The (1,4-diazabutadiene)bis(alkene)nickel(0) complexes (iPr2Ph)2-dadNi(C2H4)2 [(iPr2Ph)2-dad = 2,6-iPr2C6H3-NCHCHN-C6H3-2,6-iPr2] (1) and (iPr2 Ph)2-dadNi(η2,η2-C6H10) (2) react with ethyne above -100°C (1) or -30°C (2) with coupling of two ethyne molecules to afford the dinuclear complex [(iPr2Ph)2- dadNi]2(C4H4) (3) which contains a ferrol-type nickelacyclopentadiene-nickel(0) bonding element. A single-crystal X-ray structure study of 3 revealed strongly distorted coordination geometries of the nickel centers, which are also present in solution at low temperature (1H, 13C-NMR). At higher temperatures dynamic processes take place by which the coordinative distortions at the nickel centers are reversed and the bonding situations of the nickel atoms are exchanged. However, a rotation of the phenyl groups around the NC bonds can be excluded. Similarly, [(Me2Ph)2-dadNi]2(C4H4) (4) has been obtained and characterized. © 1990.