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Abstract:
The Ni-catalyzed cyclooligomerization of acetylene according to Reppeprobably proceeds stepwise via a nickelacyclopentadiene intermediate. By reaction of 1 with ethyne in excess and iPr2PCH2CH2PiPr2 in pentane at −78°C (!) it has now been possible for the first time to obtain a NiC4H4-complex via 2 and to characterize it IR and NMR spectroscopically. In the formula of 2 on the right a Ni(iPr2PCH2CH2PiPr2) unit has been omitted.