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Abstract:
Tris(ethene)nickel(0) reacts with tmeda and butadiene in ether below −40°C to yield a deep-red solution of (tmeda)Ni(η2-C4H6)2 (3a), from which red crystals of the thermolabile dinuclear complex {(tmeda)Ni(η2-C4H6)}2(η2,η2-C4H6) (3b) can be separated. Results in the formation of mononuclear 3a, which also forms upon dissociation of 3b in solution, was identified from its 1H and 13C NMR spectra. Above −40°C, 3a,b decompose in solution, which coupling of the butadiene ligands to afford Ni(η3,η3,η2-C12H18), which was shown to be an intermediate of the nickel-catalyzed cyclotrimerisation reaction of butadiene. Thus 3a,b are the first butadiene complexes of nickel that are catalytically active despite the presence of stabilizing ligands.
