Diazadiene als Steuerliganden in der Homogenen Katalyse, VIII [1] Katalytische Trimerisierung substituierter Acetylencarbonsäureester und Isolierung eines Acetylendicarbonsäureester-Diazadien-Nickel(0)-Addukts / Diazadienes as Controlling Ligands in Homogeneous Catalysis, VIII [1] Catalytic Trimerization of Substituted Acetylene Carbonic Acid Esters and Isolation of an Acetylene Dicarbonic Acid Ester Diazadiene Nickel(0) Adduct

Nickel(0) complexes of diazadienes (dad = RN = CR' - CR ' = NR ) catalyse the trimerization of esters of 2-butynoic acid, phenylpropynoic acid and butynedioic acid to give hexasubstituted benzenes with the unsymmetrical esters 2 as the main products. A primary adduct 7 of acetylene dicarboxylic acid dimethyl ester of the type (dad)Ni(alkyne) could be isolated and characterized by 1H NMR, IR and UV spectroscopy. According to their characteristic CT absorption. 7 and its analogues are shown to persist during catalysis as an active species