Diazadien-Nickel-Komplexe, I: Bis(diazadien)-nickel(O) und Bromo-diazadien-nickel(I) / Diazadiene Nickel Complexes, I: Bis(diazadiene) Nickel(O) and Bromo-diazadiene Nickel(I)

Abstract Reduction of anhydrous nickel(II) compounds in the presence of diazadienes RN=CR'-CR' = NR, |(DAD), yields (DAD) 2 Ni(0). This complex 1 with R = CH(i-C 3 H 7 ) 2 is especially reactive and comproportionates with DADNiBr 2 (2) to yield the bromobridged dimeric nickel(I) species (DADNiBr) 2 (3). The crystal and molecular structure of 3 has been determined by single crystal X-ray diffraction: Space group Pbca with a = 1225.8(12), b = 1474.8(14) and c = 2167.4(22) pm; Ra = 0.076, 1034 reflections. Catalytic tetramerisation of substituted alkynes with 1 is discussed in view of the very easy formation of dimers 3.