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Abstract

Displacement of the alkene ligand in Ligand-Ni(0)(1,6-diene) complexes by 1,6-heptadiyne, the parent 1,6-diyne, affords the complexes (Me₃P)Ni(η²,η²-C₇H₈) (1) and (Ph₃P)Ni(η²,η²-C₇H₈) (2). According to an X-ray structure analysis of the PMe₃ derivative 1 the nickel atom is ideally trigonal-planar coordinated by the phosphane and both C≡C bonds. The increased stability of the complexes as compared to Ligand-Ni(HC≡CH)₂ complexes is referred to the strong chelating effect which is special to the 1,6-functionalization. The compounds can be considered to be model complexes for the key intermediates of numerous transition metal-mediated coupling reactions of (substituted and unsubstituted) 1,6-diynes.